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Filed Pursuant to Rule 424(b)(5)
Registration File Number 333-136921

PROSPECTUS SUPPLEMENT

TO PROSPECTUS DATED AUGUST 28, 2006

1,600,000 Shares

Common Shares of Beneficial Interest

Washington Real Estate Investment Trust is selling all of the shares. Our shares are listed on The New York Stock Exchange under the symbol “WRE.” The closing price on The New York Stock Exchange on May 31, 2007 was $37.59 per share.

The underwriter has an option to purchase a maximum of 240,000 additional shares to cover over-allotments of shares.

Investing in our shares involves risks. See the “Risk Factors” section in our Annual Report on Form 10-K for the year ended December 31, 2006.

Delivery of the shares will be made on or about June 6, 2007.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus to which it relates is truthful or complete. Any representation to the contrary is a criminal offense.

Robert W. Baird & Co.

The date of this prospectus supplement is June 1, 2007.

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PROSPECTUS SUPPLEMENT

PROSPECTUS

You should rely only on the information contained in this document or to which we have referred you. We have not authorized anyone to provide you with information that is different. This document may only be used where it is legal to sell these securities. The information in this document may only be accurate on the date of this document.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary may not contain all of the information that may be important to you. You should read this prospectus supplement, the accompanying prospectus and the documents incorporated and deemed to be incorporated by reference into the prospectus, including the financial data and the related notes, in their entirety before making an investment decision. When used in this prospectus supplement, the terms “we,” “our,” “us” and “WRIT” refer to Washington Real Estate Investment Trust.

WRIT

Washington Real Estate Investment Trust is a self-administered, self-managed equity real estate investment trust. Our business consists of the ownership and operation of income-producing real properties. We have a fundamental strategy of regional focus, diversification by property type and conservative capital management. Our principal objective is to invest in high quality properties in prime locations, then proactively manage, lease and develop ongoing capital improvement programs to improve their long-term economic performance. On March 31, 2007, we owned 85 properties, consisting of 25 office buildings, 14 medical office buildings, 14 retail shopping centers, 9 multifamily buildings and 23 industrial/flex properties, and land for development.

While we have historically focused most of our investments within the greater Washington-Baltimore region, in order to maximize acquisition opportunities, we consider investments as far north as Philadelphia, Pennsylvania and as far south as Richmond, Virginia.

Our principal offices are located at 6110 Executive Boulevard, Suite 800, Rockville, Maryland 20852. Our telephone number there is (301) 984-9400.

Recent Developments

We have entered into multiple purchase agreements to acquire Woodholme Medical Office Building and Woodholme Center, a mixed-use development consisting of a five-story medical office building and a four-story general purpose office building located in Baltimore County, Maryland, for approximately $49 million, which will include the assumption of approximately $21.2 million of mortgage debt. The Woodholme Medical Office Building consists of approximately 125,000 net rentable square feet and the Woodholme Center consists of approximately 73,000 net rentable square feet. We expect to fund the cash portion of the purchase price of the properties with borrowings under our lines of credit. We anticipate closing of this acquisition to take place shortly following this offering.

We have entered into multiple purchase agreements to acquire Ashburn Farm Office Park, located in Loudon County, Virginia, a portfolio of three multi-story medical office buildings which consists of approximately 75,400 net rentable square feet located in Loudon County, Virginia, for approximately $23 million, which will include the assumption of approximately $5.6 million of mortgage debt. We expect to fund the cash portion of the purchase price of the properties with borrowings under our lines of credit. We anticipate closing of this acquisition to take place shortly following this offering.

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The Offering

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USE OF PROCEEDS

We estimate that the net proceeds from the sale of the shares we are offering with this prospectus supplement, assuming no exercise of the underwriter’s over-allotment option, will be approximately $57.7 million. “Net proceeds” is what we expect to receive after paying expenses of the offering, which we estimate will be approximately $200,000, and the deduction of the underwriting discount. We intend to use the net proceeds of this offering to repay borrowings outstanding under our lines of credit which were incurred principally to fund property acquisitions. As of May 31, 2007, borrowings under our lines of credit bore interest at a weighted average rate of approximately 5.76% per annum and totaled $119.2 million, including approximately $28 million borrowed on May 31, 2007 in anticipation of the acquisition of Woodholme Medical Office Building and Woodholme Center. The lines of credit have maturity dates between July 2008 and November 2010.

UNDERWRITING

Under the terms and subject to the conditions contained in an underwriting agreement dated June 1, 2007, we have agreed to sell to Robert W. Baird & Co., Incorporated all of the shares offered hereby.

The underwriting agreement provides that the underwriter is obligated to purchase all of the shares in the offering if any are purchased, other than the shares covered by the over-allotment option described below.

We have granted to the underwriter a 30-day option to purchase up to 240,000 additional shares at the initial public offering price less the underwriting discounts and commissions. The option may be exercised only to cover any over-allotments in the sale of the shares.

The underwriter proposes to offer the shares initially at the public offering price on the cover page of this prospectus supplement and to selling group members at that price less a selling concession of $0.40 per share. The underwriter and selling group members may allow a discount of $0.10 per share on sales to other broker/dealers. After the initial public offering, the underwriter may change the public offering price and concession and discount to broker/dealers.

The following table summarizes the compensation and estimated expenses we will pay:

We have agreed that we will not offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, or file with the Securities and Exchange Commission a registration statement under the Securities Act of 1933 relating to, any of our common shares of beneficial interest or securities convertible into or exchangeable or exercisable for any of our common shares of beneficial interest, or publicly disclose the intention to make any offer, sale, pledge, disposition or filing, without the prior written consent of Robert W. Baird & Co., Incorporated for a period of 60 days after the date of this prospectus, except issuances pursuant to the exercise of employee stock options outstanding on the date hereof or pursuant to our dividend reinvestment plan. However, in the event that either (1) during the last 17 days of the “lock-up” period, we release earnings results or material news or a material event relating to us occurs or (2) prior to the expiration of the ‘lock-up’ period, we announce that we will release earnings results during the 16-day period beginning on the last day of the ‘lock-up’ period, then in either case the expiration of the ‘lock-up” will be extended until the expiration of the 18-day period beginning on the date of the release of the earnings results or the occurrence of the material news or event, as applicable, unless Robert W. Baird & Co., Incorporated waives, in writing, such an extension.

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Our executive officers and trustees have agreed that they will not offer, sell, contract to sell, pledge or otherwise dispose of, directly or indirectly, any of our common shares of beneficial interest or securities convertible into or exchangeable or exercisable for any of our common shares of beneficial interest, enter into a transaction that would have the same effect, or enter into any swap, hedge or other arrangement that transfers, in whole or in part, any of the economic consequences of ownership of our common shares of beneficial interest, whether any of these transactions are to be settled by delivery of our common shares of beneficial interest or other securities, in cash or otherwise, or publicly disclose the intention to make any offer, sale, pledge or disposition, or to enter into any transaction, swap, hedge or other arrangement, without, in each case, the prior written consent of Robert W. Baird & Co., Incorporated for a period of 60 days after the date of this prospectus supplement. However, in the event that either (1) during the last 17 days of the ‘lock-up” period, we release earnings results or material news or a material event relating to us occurs or (2) prior to the expiration of the “lock-up” period, we announce that we will release earnings results during the 16-day period beginning on the last day of the “lock-up” period, then in either case the expiration of the “lock-up” will be extended until the expiration of the 18-day period beginning on the date of the release of the earnings results or the occurrence of the material news or event, as applicable, unless Robert W. Baird & Co., Incorporated waives, in writing, such an extension.

We have agreed to indemnify the underwriter against liabilities under the Securities Act, or contribute to payments that the underwriter may be required to make in that respect.

In connection with the offering the underwriter may engage in stabilizing transactions, over-allotment transactions, syndicate covering transactions, and penalty bids in accordance with Regulation M under the Securities Exchange Act of 1934.

These stabilizing transactions, syndicate covering transactions and penalty bids may have the effect of raising or maintaining the market price of our shares or preventing or retarding a decline in the market price of the shares. As a result, the price of our shares may be higher than the price that might otherwise exist in the open market. These transactions may be effected on the New York Stock Exchange or otherwise and, if commenced, may be discontinued at any time.

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A prospectus in electronic format may be made available on the web site maintained by the underwriter, or selling group members, if any, participating in this offering and the underwriter may distribute prospectuses electronically.

The underwriter from time to time provides investment banking and financial advisory services to us. It has received customary fees and commissions for these transactions.

EXPERTS

Ernst & Young LLP, our independent registered public accounting firm, has audited our consolidated financial statements and schedule included in our Annual Report on Form 10-K for the year ended December 31, 2006, and management’s assessment of the effectiveness of our internal control over financial reporting as of December 31, 2006, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements and schedule and management’s assessment are incorporated by reference in reliance on Ernst & Young LLP’s reports given on their authority as experts in accounting and auditing.

The historical summaries of gross income and direct operating expenses of (i) Albemarle Point for the year ended December 31, 2004, (ii) Alexandria Professional Center, 9707 Medical Center Drive, 15001 Shady Grove Road, Randolph Shopping Center, Montrose Shopping Center and Plumtree Medical Center for the year ended December 31, 2005, (iii) the Matan Portfolio and 15005 Shady Grove Road for the year ended December 31, 2005 and (iv) 270 Technology Park, Monument II and 2440 M Street for the year ended December 31, 2006, are incorporated in reliance on the reports dated August 10, 2005, June 23, 2006, September 8, 2006 and May 17, 2007, respectively, of Argy, Wiltse & Robinson, P.C., which we also incorporate by reference, and on the authority of that firm as experts in accounting and auditing.

LEGAL MATTERS

Arent Fox LLP, Washington, D.C., our legal counsel, will issue opinions about the valid issuance of the shares offered by this prospectus supplement and tax matters relating to the qualification of WRIT as a real estate investment trust. Vinson & Elkins L.L.P., Washington, D.C., will issue an opinion about some legal matters with respect to the shares offered by this prospectus supplement for the underwriter.

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PROSPECTUS

$500,000,000

WASHINGTON REAL ESTATE INVESTMENT TRUST

6110 EXECUTIVE BOULEVARD, SUITE 800

ROCKVILLE, MARYLAND 20852

(301) 984-9400

COMMON SHARES

PREFERRED SHARES

COMMON SHARE WARRANTS

DEBT SECURITIES

Washington Real Estate Investment Trust may offer from time to time its

up to an aggregate amount of $500,000,000 or an equivalent amount in one or more foreign currencies or composite currencies, including European currency units.

We may sell the offered securities in one or more ways: directly, through agents we designate from time to time or to or through underwriters or dealers. If we use any agents or underwriters in selling any of the offered securities, the prospectus supplement that we will provide will identify the agents and underwriters and describe any applicable purchase price, fee, commission or discount arrangement.

Our common shares of beneficial interest are listed on the New York Stock Exchange under the symbol “WRE”. Where applicable, the prospectus supplement will contain information on any listing on a securities exchange of securities covered by that prospectus supplement.

Investing in these securities involves risks that are described in the “Risk Factors” section of our Annual Report on Form 10-K for the year ended December 31, 2005.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the offered securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is August 28, 2006.

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YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS AND THE ACCOMPANYING PROSPECTUS SUPPLEMENT OR INCORPORATED BY REFERENCE IN THESE DOCUMENTS. NO DEALER, SALESPERSON OR OTHER PERSON IS AUTHORIZED TO GIVE ANY INFORMATION OR TO REPRESENT ANYTHING NOT CONTAINED OR INCORPORATED BY REFERENCE IN THIS PROSPECTUS OR THE ACCOMPANYING PROSPECTUS SUPPLEMENT. IF ANYONE PROVIDES YOU WITH DIFFERENT, INCONSISTENT OR UNAUTHORIZED INFORMATION OR REPRESENTATIONS, YOU MUST NOT RELY ON THEM. THIS PROSPECTUS AND THE ACCOMPANYING PROSPECTUS SUPPLEMENT ARE AN OFFER TO SELL ONLY THE SECURITIES OFFERED BY THESE DOCUMENTS, BUT ONLY UNDER CIRCUMSTANCES AND IN JURISDICTIONS WHERE IT IS LAWFUL TO DO SO. THE INFORMATION CONTAINED IN THIS PROSPECTUS OR ANY PROSPECTUS SUPPLEMENT IS CURRENT ONLY AS OF THE DATE ON THE FRONT OF THOSE DOCUMENTS.

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the SEC using a shelf registration process. Under this process, we may sell the common shares, the preferred shares, the common share warrants and the debt securities described in this prospectus in one or more offerings up to a total amount of $500,000,000. We may sell the offered securities in any combination—separately, together or as units with other offered securities—in one or more series or amounts and at prices and on other terms that we determine at the time of sale.

This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement containing information about the specific terms and method of the offering. The prospectus supplement may also add, update or change the information in this prospectus. You should read both this prospectus and the applicable prospectus supplement, together with additional information that we refer to under “Where You Can Find More Information,” before making an investment decision.

WASHINGTON REAL ESTATE INVESTMENT TRUST

Washington Real Estate Investment Trust, which is also known as WRIT, is a self-administered and self-managed equity real estate investment trust investing in income producing properties in the Mid-Atlantic area with a principal focus in the greater Washington-Baltimore region. As of June 30, 2006, WRIT owned a diversified portfolio of 77 properties consisting of 14 retail centers, 21 office properties, 11 medical office properties, 22 industrial/flex properties, 9 multi-family properties and land for development.

WRIT’s principal objective is to invest in high quality real estate in prime locations and proactively manage, lease and develop its properties through ongoing capital improvement programs to improve their economic performance. During the quarter ended June 30, 2006, the economic occupancy rates of our properties were:

WRIT’s total debt on June 30, 2006 was approximately $816.5 million.

WRIT’s funds from operations (“FFO”) per share has increased every year for 33 consecutive years. WRIT concentrates on increasing its income from operations and funds from operations to achieve its objective of paying increasing dividends to its shareholders. Funds from operations is a supplemental measure of real estate companies’ operating performance. As of January 1, 2000, the National Association of Real Estate Investment Trusts (“NAREIT”) defines funds from operations as income available for common shareholders before depreciation and amortization of real estate assets and before extraordinary items, less gains on sale of real estate. Prior to January 1, 2000 funds from operations also excluded significant nonrecurring events. Funds from operations does not replace net income as a measure of performance or net cash provided by operating activities as a measure of liquidity. Rather, funds from operations has been adopted by real estate investment trusts to provide a consistent measure of operating performance in the industry. WRIT has paid consecutive quarterly dividends to its shareholders for 45 years, and the annual dividend paid has increased every year for the past 36 years.

WRIT is a Maryland REIT, successor to a trust founded in 1960. Our principal offices are located at 6110 Executive Boulevard, Suite 800, Rockville, Maryland 20852, telephone (301) 984-9400 or (800) 565-9748.

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USE OF PROCEEDS

Unless we state otherwise in our prospectus supplement, we intend to use the net proceeds from the sale of offered securities for general business purposes, including the acquisition, renovation, expansion or improvement of income-producing properties or the repayment of debt. We expect that properties that we purchase in the future will be of the same general character as those we presently own. We may also use the net proceeds to acquire another REIT or other company that invests in income producing properties, although we do not have a specific plan to do so. Until we use the net proceeds for the purposes described above, we may invest them in short-term income producing investments, such as commercial paper, government securities or money market funds that invest in government securities and/or commercial paper.

RATIOS OF EARNINGS TO FIXED CHARGES

The following table sets forth WRIT’s ratios of earnings to fixed charges for the periods shown:

We computed the ratios of earnings to fixed charges by dividing earnings by fixed charges. For this purpose, earnings consist of income from continuing operations plus fixed charges. Fixed charges consist of interest expense, including interest costs capitalized, and the amortized costs of debt issuance.

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DESCRIPTION OF SHARES

General

WRIT is authorized to issue 100,000,000 common shares with a par value of $.01 per share. Under Maryland law and WRIT’s declaration of trust, WRIT may increase the aggregate number of authorized common shares without shareholder approval. As of June 30, 2006, there were 44,998,159 common shares outstanding.

WRIT’s board of trustees intends to propose to amend WRIT’s declaration of trust to authorize WRIT to issue preferred shares with a par value of $.01 per share. The preferred shares amendment will also include modifications to the declaration of trust to distinguish the rights of the holders of common shares and the holders of preferred shares. Adoption of the preferred shares amendment will require the approval of the holders of 70% of WRIT’s outstanding common shares at a meeting of WRIT’s shareholders. No preferred shares may be issued prior to the adoption of the preferred shares amendment.

We describe below some of the terms of the common shares and preferred shares. In addition, we describe selected provisions of WRIT’s declaration of trust and selected provisions of Maryland law. We will describe in a prospectus supplement the specific terms of any series of preferred shares. The descriptions in this prospectus and the applicable prospectus supplement are not complete and may not contain all of the information that may be important to you. To obtain further information, you should refer to the provisions of WRIT’s declaration of trust dated April 5, 1996, the amendments to the declaration of trust dated September 21, 1998, June 24, 1999 and May 31, 2006, the bylaws, the preferred shares amendment to be proposed and any applicable amendment to the declaration of trust fixing the terms of a series of preferred shares.

Common shares

Holders of common shares are entitled to receive dividends and distributions when and as declared by the board of trustees after payment of, or provision for, any cumulated dividends and distributions on and any required redemptions of any preferred shares then outstanding. Holders of common shares have one vote per share. Voting rights are not cumulative. This means that in the election of trustees at a shareholders’ meeting, the holders of a majority of the outstanding common shares can cast all of their votes for each trustee to be elected and elect all of the trustees then standing for election, and the votes held by the holders of the remaining common shares will not be sufficient to elect any trustee.

The declaration of trust establishes the number of trustees at not less than three nor more than eleven and divides the trustees into three classes to be elected on a staggered basis. Those trustees are elected by the holders of the common shares. If the preferred shares amendment is proposed and adopted, the board of trustees could establish a series of preferred stock having the right to elect up to two additional trustees, but less than a majority of the trustees, under specified circumstances and for specified periods, which we describe below.

Under the preferred shares amendment, the board of trustees could reclassify any unissued common shares in one or more classes and could amend the declaration of trust to decrease, as well as increase, the aggregate number of common shares authorized without shareholder approval.

Upon liquidation of WRIT, holders of common shares would receive their pro rata share of the distributable assets of WRIT remaining after the satisfaction of preferential rights of any preferred shares and the satisfaction of all debts and liabilities of WRIT. Holders of common shares do not have any preference, conversion, exchange, preemptive or redemption rights.

The common shares are listed on the New York Stock Exchange. Computershare Limited, Jersey City, New Jersey is the transfer agent for the common shares.

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Preferred shares

General. The following description of preferred shares is based upon the terms of the preferred shares amendment that WRIT’s board of trustees would propose to shareholders prior to offering preferred shares. Following shareholder approval of the preferred shares amendment, the board of trustees would be authorized, without further shareholder action, to issue preferred shares, in one or more series, with designations, preferences, rights and limitations as the board of trustees approves. Under the preferred shares amendment, WRIT would be authorized to issue 5,000,000 preferred shares with a par value of $.01 per share, but the board of trustees could amend the declaration of trust to increase or decrease the aggregate number of preferred shares authorized without shareholder approval.

The preferred shares are proposed to have the dividend, liquidation, redemption, conversion and voting rights described below unless the prospectus supplement relating to a particular series of preferred shares indicates otherwise. You should refer to the prospectus supplement relating to the particular series of preferred shares offered for specific terms, including:

The prospectus supplement also may discuss the federal income tax considerations applicable to the preferred shares offered.

The preferred shares, when issued, will be fully paid and nonassessable. Unless otherwise indicated in the prospectus supplement relating to a particular series of preferred shares, each series of preferred shares will rank equally with each other series of preferred shares as to dividends and distributions in the event of a liquidation and, in all cases, will be senior to the common shares.

Dividend Rights. Holders of preferred shares of each series will be entitled to receive, when declared by the board of trustees, cash dividends at the rates and on the dates described in the prospectus supplement relating to the series of preferred shares, out of WRIT’s assets legally available for that purpose. The rates may be fixed or variable or both and may be cumulative, noncumulative or partially cumulative.

As long as any preferred shares are outstanding, no dividends will be declared or paid and no distributions will be made on the common shares, other than a dividend payable in common shares, unless the accrued dividends on each series of preferred shares have been fully paid or declared and set apart for payment and, if the applicable prospectus supplement so indicates, WRIT has set apart any required amounts for any sinking funds for each series of preferred shares.

When dividends are not paid in full upon any series of preferred shares and any other series of preferred shares ranking equally as to dividends with that series of preferred shares, all dividends declared upon that series of preferred shares and any other series of preferred shares ranking equally as to dividends will be paid ratably in proportion to the amount of accrued dividends to which they are entitled.

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Each series of preferred shares will be entitled to dividends as described in the prospectus supplement relating to that series. Different series of preferred shares may be entitled to dividends at different dividend rates or based upon different methods of determination.

Rights Upon Liquidation. Upon any voluntary or involuntary liquidation, dissolution or winding up of WRIT, the holders of each series of preferred shares will be entitled to receive out of the assets of WRIT available for distribution to shareholders the amount stated or determined on the basis described in the prospectus supplement relating to that series. If, upon any voluntary or involuntary liquidation, dissolution or winding up of WRIT, the amounts payable on the preferred shares of any series and any other shares of stock of WRIT ranking as to distribution equally with that series of preferred shares are not paid in full, the holders of preferred shares of that series and of the other shares will share ratably in any distribution of assets of WRIT in proportion to the full preferential amounts to which they are entitled or on another basis as described in the applicable prospectus supplement. Any rights of the holders of any series of preferred shares to participate in the assets of WRIT remaining after the holders of other series of preferred shares have been paid their liquidation preferences upon any liquidation, dissolution or winding up of WRIT will be described in the prospectus supplement relating to that series.

Redemption. Subject to the terms of WRIT’s outstanding debt, a series of preferred shares may be redeemable, in whole or in part, at the option of WRIT or the option of the holder. In each case, the applicable prospectus supplement will describe the terms of any redemption rights including the number of shares, the price, the dates and the type of consideration.

If, after giving notice of redemption to the holders of a series of preferred shares, WRIT deposits with a designated bank funds sufficient to redeem those preferred shares, then after that deposit, all preferred shares called for redemption will no longer be outstanding for any purpose, other than the right to receive the redemption price and the right to convert those preferred shares into other classes of capital stock of WRIT.

Conversion Rights. A series of preferred shares may be convertible. The prospectus supplement for any series of preferred shares will describe the terms on which shares of that series may be converted into common shares or any other security issuable by WRIT.

Voting Rights. A holder of preferred shares will not be entitled to vote except as indicated in the prospectus supplement relating to a particular series of preferred shares or except as expressly required by Maryland law. Voting rights are proposed to be limited. The board of trustees may not establish a series of preferred shares having voting rights in addition to the following:

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Except as indicated otherwise in the prospectus supplement relating to a particular series of preferred shares, each full share will be entitled to one vote on matters on which holders of preferred shares are entitled to vote and fractional shares will not be entitled to any vote.

Transfer Agent and Registrar. WRIT will select the transfer agent, registrar and dividend disbursement agent for a series of preferred shares, which will be described in the applicable prospectus supplement. The registrar for preferred shares will send notices to shareholders of any meetings at which holders of preferred shares have the right to vote on any matter.

Business Combination Provisions

WRIT’s declaration of trust provides that any merger, consolidation or liquidation of WRIT, or any sale of all or substantially all of its assets, must be approved by a majority of WRIT’s trustees. In addition, if any of those transactions involves a related shareholder, the transaction must be approved by a majority of trustees not appointed or nominated by or acting on behalf of the related shareholder or an affiliate or associate of the related shareholder. A related shareholder is a person or entity beneficially owning, directly or indirectly, 5% or more of the outstanding shares, including among his or its shares those owned by an affiliate or associate.

As permitted by Maryland law, WRIT has expressly elected to be governed by the special voting requirements of Title 3, Subtitle 6, of the Maryland Corporations and Associations Article, which we refer to as the Special Voting Article. The Special Voting Article establishes special requirements with respect to a business combination between an interested stockholder and a Maryland corporation unless exemptions are applicable. The Special Voting Article prohibits a merger and other specified or similar transactions between a Maryland corporation and an interested stockholder for a five-year period and requires a super majority vote for those transactions after the end of the five-year period. For the purposes of the Special Voting Article and the Control Share Article, which we describe below, a Maryland corporation includes a Maryland real estate investment trust. We refer to them collectively in this section as a Maryland company.

An interested stockholder is a person owning beneficially, directly or indirectly, 10% or more of the outstanding voting stock of a Maryland company. Business combinations include any merger or similar transaction subject to a statutory vote and additional transactions involving transfers of assets or securities in specified amounts to interested stockholders or their affiliates.

Unless an exemption is available, a business combination may not be consummated between a Maryland company and an interested stockholder for a period of five years after the date on which the shareholder became an interested stockholder. After that five-year period, a business combination may not be consummated unless recommended by the board of the Maryland company and approved by the affirmative vote of at least 80% of the votes entitled to be cast by all holders of outstanding shares of voting stock and 66 ²/3% of the votes entitled to be cast by all holders of outstanding shares of voting stock other than the interested stockholder. These provisions do not apply if the company’s stockholders receive a minimum price, as defined in the Special Voting Article, for their shares and they receive the consideration in cash or in the same form as previously paid by the interested stockholder for its shares and if other conditions are met.

A business combination with an interested stockholder that is approved by the board of a Maryland company at any time before an interested stockholder first becomes an interested stockholder is not subject to the

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special voting requirements or fair price provisions of the Special Voting Article. An amendment to a Maryland company’s charter electing not to be subject to the foregoing requirements must be approved by the affirmative vote of at least 80% of the votes entitled to be cast by all holders of outstanding shares of voting stock and 66 ²/3% of the votes entitled to be cast by holders of outstanding shares of voting stock who are not interested stockholders. The amendment will not be effective until 18 months after the vote of stockholders and does not apply to any business combination of a company with a stockholder who was an interested stockholder on the date of the stockholder vote.

As permitted by Maryland law, WRIT has also expressly elected to be governed by the control share provisions of Title 3, Subtitle 7, of the Maryland Corporations and Associations Article, which we refer to as the Control Share Article. Under the Control Share Article, control shares of a Maryland company acquired in a control share acquisition have no voting rights except to the extent approved by a vote of two-thirds of the votes entitled to be cast on the matter, excluding shares of stock owned by the acquiror or by officers or directors who are employees of the company. Control shares are voting shares of stock that, if aggregated with all other shares of stock previously acquired by the acquiror, would entitle the acquiror to exercise voting power in electing directors or trustees within one of the following ranges of voting power: (1) 20% or more but less than 33 ¹/3%, (2) 33 ¹/3% or more but less than a majority or (3) a majority of all voting power. Control shares do not include shares the acquiring person is then entitled to vote as a result of having previously obtained shareholder approval. A control share acquisition is, subject to specified exceptions, the acquisition of, ownership of or the power to direct the exercise of voting power with respect to control shares.

A person who has made or proposes to make a control share acquisition upon satisfaction of specified conditions, including an undertaking to pay expenses, may compel the board of directors to call a special meeting of shareholders to be held within 50 days of demand to consider the voting rights of the shares. If no request for a meeting is made, the Maryland company may itself present the question at any shareholders’ meeting.

If voting rights for control shares are not approved at the meeting or if the acquiring person does not deliver an acquiring person statement as permitted by the statute, then subject to specified conditions and limitations, the Maryland company may redeem any or all of the control shares, except those for which voting rights have previously been approved, for fair value, without regard to the absence of voting rights for the control shares. Fair value will be determined as of the date of the meeting of the shareholders at which the voting rights of the control shares are considered but not approved. If no meeting is held, fair value will be determined as of the date of the last acquisition of control shares by the acquiring person. If voting rights for control shares are approved at a shareholders’ meeting and the acquiror becomes entitled to a majority of the shares entitled to vote, all other shareholders may exercise appraisal rights. The fair value of the shares as determined for purposes of the appraisal rights may not be less than the highest price per share paid in the control share acquisition. Some limitations and restrictions otherwise applicable to the exercise of dissenters’ rights do not apply in the context of a control share acquisition.

The Control Share Article does not apply to

The Special Voting Article and the Control Share Article may have the effect of discouraging unilateral tender offers or other takeover proposals, which some shareholders might consider in their interests or that might provide a substantial premium for their shares. The Control Share Article in particular has the effect of making a unilateral tender offer or other takeover of WRIT more difficult. The provisions could also have the effect of insulating current management against the possibility of removal and could, by possibly reducing temporary fluctuations in market price caused by accumulations of shares, deprive shareholders of opportunities to sell their shares at a temporarily higher market price.

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Restrictions on Ownership

For WRIT to qualify as a REIT under the Internal Revenue Code, in any taxable year, not more than 50% in value of WRIT’s outstanding shares may be owned, directly or indirectly, by five or fewer individuals during the last six months of the year, and the shares must be owned by 100 or more persons during at least 335 days of a taxable year or a proportionate part of a taxable year less than 12 months. To meet these and other requirements, the trustees have the power to redeem or prohibit the transfer of a sufficient number of shares to maintain or bring the ownership of the shares into conformity with the requirements. In that regard, the declaration of trust provides that if any person is or becomes at any time the beneficial owner, directly or indirectly, of more than 10% of WRIT’s outstanding shares or if WRIT’s tax status is or can be endangered by the purchase or retention of shares by any person, the trustees may in their sole discretion (1) repurchase any or all shares held by that person or (2) refuse to sell, transfer or deliver shares to that person. The preferred shares amendment if adopted would amend this provision in the declaration of trust to clarify that the 10% threshold applies to all of the outstanding shares computed on the basis of the value of the shares.

The purchase price for any shares repurchased will be (1) the cost or the last sale price of the shares as of the date immediately preceding the day on which the demand for repurchase is mailed, whichever price is higher, or (2) the amount provided in the terms of that class or series of shares called for repurchase, if the preferred shares amendment is adopted. From the date fixed for repurchase by the trustees, and so long as payment of the purchase price for the shares to be repurchased has been made or provided for, the holder of any shares called for repurchase will cease to be entitled to distributions, voting rights and other benefits with respect to those shares, except the right to payment of the purchase price for the shares.

The declaration of trust includes provisions to ensure that any rent paid to WRIT by a sister corporation not become disqualified as rent from real property by virtue of Section 856(d)(2)(B) of the Internal Revenue Code. For purposes of these provisions, a sister corporation is a corporation the shares of which are owned by exactly or substantially the same persons and in exactly or substantially the same numbers as are the shares of WRIT. Under these provisions, if the trustees, at any time and in good faith, are of the opinion that direct or indirect ownership of shares has or may become concentrated to an extent that would cause any rent to be paid to WRIT by a sister corporation, if one existed, to fail to qualify or be disqualified as rent from real property by virtue of Section 856(d)(2)(B) of the Internal Revenue Code, the trustees have the power

These provisions will apply even if a sister corporation does not exist (1) at the time the trustees determine that the ownership of shares has or may become so concentrated, or (2) at the time the trustees call shares for purchase or refuse to register the transfer of shares. The purchase price for the shares purchased under these provisions will be equal to

From the date fixed for purchase by the trustees, the holder of any shares called for purchase will cease to be entitled to dividends, voting rights and other benefits with respect to those shares, except the right to payment of the purchase price fixed as described above.

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To further assure that ownership of the shares does not become concentrated, the declaration of trust provides that if any transfer of shares would prevent amounts received by WRIT from a sister corporation, if one existed, from qualifying as rents from real property as defined in Section 856(d) of the Internal Revenue Code, by virtue of the application of Section 856(d)(2)(B) of the Internal Revenue Code, the transfer will be void from inception and the intended transferee of the shares will be treated as never having had an interest in those shares. If this provision is invalid by virtue of any legal decision, statute, rule or regulation, then the transferee of the shares will be treated as having acted as an agent on behalf of WRIT in acquiring those shares and as holding those shares on WRIT’s behalf. Furthermore, the declaration of trust provides that shareholders will be required upon demand to disclose to the trustees in writing information with respect to their direct and indirect ownership of the shares that the trustees deem necessary to determine whether WRIT satisfies the provisions of Sections 856(a)(5) and (6) and Section 856(d) of the Internal Revenue Code or the regulations under such sections or to comply with the requirements of any other taxing authority.

Under an amendment to the declaration of trust, a provision has been added to the declaration of trust specifying that (1) the share ownership limitation provisions described above, or any other provision of the declaration of trust, will not preclude the settlement of any transaction entered through the facilities of the New York Stock Exchange or any other national securities exchange or automated inter-dealer quotation system and (2) the occurrence of the settlement of any transaction will not negate the effect of the share ownership limitation provisions or any other provision of the declaration of trust.

The share ownership limitation provisions, like the business combination provisions, may deter or render more difficult an attempt by a third party to obtain control of WRIT if the attempt is not supported by the board of trustees.

Taxation

WRIT has elected to be taxed as a REIT under the Internal Revenue Code. A REIT that meets specified qualifications is relieved of federal income taxes on ordinary income and capital gains distributed to shareholders. In the opinion of Arent Fox PLLC, legal counsel for WRIT, WRIT has qualified as a REIT for the years 2001-2005 and its present and contemplated method of operation will put it in a position to continue to qualify as a REIT. David M. Osnos, a trustee, is of counsel to Arent Fox PLLC.

DESCRIPTION OF COMMON SHARE WARRANTS

WRIT may issue common share warrants for the purchase of common shares. WRIT may issue common share warrants independently or together with any other offered securities offered by any prospectus supplement. Common share warrants may be attached to or separate from the other offered securities. Each series of common share warrants will be issued under a separate warrant agreement to be entered into between WRIT and a warrant agent identified in the applicable prospectus supplement. The warrant agent will act solely as an agent of WRIT in connection with the common share warrants of a series and will not assume any obligation or relationship of agency or trust for any holders or beneficial owners of common share warrants.

The applicable prospectus supplement will describe the terms of the common share warrants, including, where applicable, the following:

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DESCRIPTION OF DEBT SECURITIES

General

WRIT will issue senior debt securities under a senior indenture dated as of August 1, 1996, as supplemented from time to time, between WRIT and The J.P. Morgan Trust Company, N.A., as senior indenture trustee, or pursuant to an additional indenture adopted by us in the future. WRIT will issue subordinated debt securities under a subordinated indenture between WRIT and a commercial bank we will select to act as subordinated indenture trustee. We use the term indenture trustee to refer to the senior indenture trustee or subordinated indenture trustee, as appropriate. We refer to the senior indenture and the subordinated indenture together as the indentures and individually as an indenture. The senior indenture and the form of the subordinated indenture are filed as exhibits to the registration statement of which this prospectus is a part. The indentures will be available for inspection at the corporate trust offices of the senior indenture trustee and the subordinated indenture trustee and as described below under “Where You Can Find More Information.” The indentures are subject to and governed by the Trust Indenture Act of 1939.

We describe below some of the terms of the debt securities and some of the provisions of the indentures. We will describe in a prospectus supplement the specific terms of the debt securities and the extent to which the provisions described below apply. The descriptions in this prospectus and the applicable prospectus supplement are not complete and may not contain all of the information that may be important to you. To obtain further information, you should refer to the provisions of the indentures and the debt securities. We have included in this prospectus references to sections of the indentures to help you locate those provisions in the indentures.

Terms

The debt securities will be direct, unsecured obligations of WRIT. The senior debt securities will rank equally with all other unsecured and unsubordinated debt of WRIT. Payments on the subordinated debt securities will be subordinated to the prior payment in full of WRIT’s senior debt, as described in this section under “Subordination.” Each indenture provides that WRIT may issue debt securities without limit as to aggregate principal amount, in one or more series, in each case as established from time to time in, or under authority granted by, a resolution of WRIT’s board of trustees or as established in one or more supplemental indentures. WRIT may issue debt securities with terms different from those of debt securities previously issued. Debt securities of one series may be issued at different times and, unless otherwise provided, a series may be reopened, without the consent of the holders of the debt securities of that series, for issuances of additional debt securities of that series. (Section 301 of each indenture).

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More than one indenture trustee may be appointed under either indenture, with each indenture trustee acting as to one or more series of debt securities. Any indenture trustee may resign or be removed as to one or more series of debt securities, and a successor indenture trustee may be appointed to act regarding that series. (Section 608 of each indenture). If two or more persons are appointed as indenture trustee regarding different series of debt securities, each will act under the applicable indenture as an indenture trustee of a trust separate from the trust administered by any other indenture trustee. (Section 609 of each indenture). Except as otherwise indicated in this prospectus, an indenture trustee may act only with respect to the one or more series of debt securities for which it is indenture trustee under the applicable indenture.

The prospectus supplement relating to the series of debt securities being offered will contain information on the specific terms of the debt securities including:

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WRIT may issue debt securities at a discount below their principal amount. If that occurs, the debt securities may provide for less than their entire principal amount to be payable upon declaration of acceleration of the maturity of the debt securities. We refer to those debt securities as original issue discount securities. The applicable prospectus supplement will describe the special U.S. federal income tax, accounting and other considerations applicable to original issue discount securities.

Except as described below under “Covenants” and as may be described in any prospectus supplement, the indentures will not contain any provisions

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The applicable prospectus supplement will provide information regarding any deletions from, modifications of, or additions to the events of default or covenants of WRIT that are described below, including any addition of a covenant or other provision providing protection for risks similar to those referred to above.

Denominations, Interest, Registration and Transfer

Unless otherwise described in the applicable prospectus supplement, the debt securities of any series issued in registered form will be issuable in denominations of $1,000 and integral multiples of $1,000, and the debt securities of any series issued in bearer form will be issuable in denominations of $5,000. (Section 302 of each indenture).

Unless otherwise described in the applicable prospectus supplement, the principal of, any premium and interest on any series of senior debt securities will be payable at the corporate trust office of the senior indenture trustee, which initially will be c/o J.P. Morgan Trust Company, National Association, 4 New York Plaza, First Floor, New York, New York 10004. Unless otherwise described in the applicable prospectus supplement, the principal of, any premium and interest on any series of subordinated debt securities will be payable at the corporate trust office of the subordinated indenture trustee. WRIT may instead pay interest on any series of debt securities by check mailed to the address of the person entitled to the payment as it appears in the applicable register for the debt securities or by wire transfer of funds to that person at an account maintained within the United States. (Sections 301, 307 and 1002 of each indenture).

Any interest not punctually paid or duly provided for on any interest payment date will cease to be payable to the holder of the debt security on the applicable regular record date and may be paid to the person in whose name the debt security is registered at the close of business on a special record date for the payment of defaulted interest to be fixed by the indenture trustee. If that occurs, notice will be given to the holder of the debt security not less than 10 days prior to the special record date. Alternatively, defaulted interest may be paid at any time in any other lawful manner. (Section 307 of each indenture).

Subject to limitations imposed upon debt securities issued in book-entry form, the debt securities of any series will be exchangeable for other debt securities of the same series and of a like aggregate principal amount and tenor of different authorized denominations upon surrender of the debt securities at the corporate trust office of the applicable indenture trustee. In addition, subject to limitations imposed upon debt securities issued in book-entry form, the debt securities of any series may be surrendered for conversion, registration of transfer or exchange at the corporate trust office of the applicable indenture trustee. Every debt security surrendered for conversion, registration of transfer or exchange must be properly endorsed or accompanied by a written instrument of transfer. No service charge will be made for any registration of transfer or exchange of any debt securities, but WRIT may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with the registration of transfer or exchange. (Section 305 of each indenture). If WRIT designates a transfer agent, in addition to the applicable indenture trustee, regarding any series of debt securities, WRIT may at any time rescind the designation of the transfer agent or approve a change in the location through which the transfer agent acts, but WRIT is required to maintain a transfer agent in each place of payment for each series of debt securities. WRIT may at any time designate additional transfer agents regarding any series of debt securities. (Section 1002 of each indenture).

Neither WRIT nor any indenture trustee will be required to:

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Merger, Consolidation or Sale

WRIT will be permitted to consolidate with, or sell, lease or convey all or substantially all of its assets to, or merge with or into, any other entity if:

Covenants

In this part of the prospectus, we use several capitalized terms to refer to defined terms. We describe the definitions of those terms after the paragraph in which we use them for the first time. The senior indenture provides for the following covenants, which we may modify or delete upon the issuance of any series of senior debt securities:

Senior Indenture Limitations on Incurrence of Debt. The senior indenture provides that WRIT will not, and will not permit any Subsidiary to, incur any additional Debt if, immediately after giving effect to the incurrence of the additional Debt and the application of the proceeds from the incurrence of the additional Debt, the aggregate principal amount of all outstanding Debt of WRIT and its Subsidiaries on a consolidated basis determined in accordance with generally accepted accounting principles is greater than 60% of the sum of, without duplication:

“Subsidiary” means a corporation, partnership or limited liability company, a majority of the outstanding voting stock, partnership interests or membership interests of which is owned or controlled, directly or indirectly, by WRIT or by one or more other Subsidiaries of WRIT. For the purposes of this definition, “voting stock” means stock having voting power for the election of directors or trustees, whether at all times or only so long as no senior class of stock has the voting power by reason of any contingency.

“Debt” of WRIT or any Subsidiary means any debt of WRIT or any Subsidiary, whether or not contingent, in connection with:

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“Disqualified Stock” means any Capital Stock that by its terms, or by the terms of any security into which it is convertible or for which it is exchangeable or exercisable, upon the happening of any event or otherwise:

“Capital Stock” means any capital stock, including preferred stock, shares, interests, participations or other ownership interests however designated and any rights, other than debt securities convertible into or exchangeable for corporate stock, warrants or options to purchase.

“Total Assets” as of any date means the sum of

“Undepreciated Real Estate Assets” as of any date means the original cost plus capital improvements of real estate assets of WRIT and its Subsidiaries on that date, before depreciation and amortization, determined on a consolidated basis in accordance with generally accepted accounting principles.

In addition to the limitations on the incurrence of Debt described above, the senior indenture provides that WRIT will not, and will not permit any Subsidiary to, incur any Secured Debt, whether owned at the date of the senior indenture or subsequently acquired, if, immediately after giving effect to the incurrence of the additional Secured Debt and the application of the proceeds, the aggregate principal amount of all outstanding Secured Debt of WRIT and its Subsidiaries on a consolidated basis is greater than 40% of WRIT’s Adjusted Total Assets. (Section 1011 of the senior indenture.) “Secured Debt” means any Debt secured by any mortgage, lien, charge, pledge, encumbrance or security interest of any kind upon any of the property of WRIT or any Subsidiary.

The senior indenture also provides that WRIT will not, and will not permit any Subsidiary to, incur any additional Debt if the ratio of Consolidated Income Available for Debt Service to the Annual Service Charge for the four consecutive fiscal quarters most recently ended before the date on which the additional Debt is to be incurred is less than 1.5 to 1.0, on a pro forma basis after giving effect to the incurrence of that Debt and to the application of the proceeds from the incurrence of that Debt. The ratio is calculated assuming that:

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“Consolidated Income Available for Debt Service” for any period means Consolidated Net Income of WRIT and its Subsidiaries

“Consolidated Net Income” for any period means the amount of consolidated net income or loss of WRIT and its Subsidiaries for that period determined on a consolidated basis in accordance with generally accepted accounting principles.

“Annual Service Charge” as of any date means the maximum amount that is payable in any period for interest on, and original issue discount of, Debt of WRIT and its Subsidiaries.

“Acquired Debt” means Debt of a person

in each case, other than Debt incurred in connection with, or in contemplation of, the person becoming a Subsidiary or the acquisition. Acquired Debt will be treated as incurred on the date of the related acquisition of assets from any person or the date the acquired person becomes a Subsidiary.

For purposes of the provisions limiting the incurrence of Debt, Debt is treated as incurred by WRIT or a Subsidiary whenever WRIT or a Subsidiary creates, assumes, guarantees or otherwise becomes liable on the Debt.

Maintenance of Total Unencumbered Assets. The senior indenture also provides that WRIT is required to maintain Total Unencumbered Assets of not less than 150% of the aggregate outstanding principal amount of WRIT’s Unsecured Debt. (Section 1012 of the senior indenture).

“Total Unencumbered Assets” means the sum of

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“Encumbrance” means any mortgage, security interest, pledge, hypothecation, assignment, deposit arrangement, encumbrance, statutory or other lien or preference, priority or other security agreement, except:

“Total Assets” as of any date means the sum of

“Unsecured Debt” means Debt of WRIT or any Subsidiary that is not secured by any mortgage, lien, charge, pledge or security interest of any kind upon any of the properties owned by WRIT or any of its Subsidiaries.

Existence. Except as described under the section below entitled “Merger, Consolidation or Sale,” WRIT will be required to do everything necessary to preserve and keep in full force and effect its existence, rights and franchises. But WRIT will not be required to preserve any right or franchise if it determines that the preservation of the right or franchise is no longer desirable in the conduct of its business. (Section 1004 of each indenture).

Maintenance of Properties. To the extent WRIT believes it necessary for the proper conduct of business, WRIT will be required to keep all of its material properties used in the conduct of its business or the business of any Subsidiary in good condition, repair and working order and supplied with all necessary equipment and to make all necessary repairs and improvements of those properties. (Section 1005 of each indenture).

Insurance. WRIT will be required to, and will be required to cause each of its Subsidiaries to, keep all of its insurable properties insured against loss or damage at least equal to their then full insurable value with insurers of recognized responsibility and, if described in the applicable prospectus supplement, having a specified rating from a recognized insurance rating service. (Section 1006 of each indenture).

Payment of Taxes and Other Claims. WRIT will be required to pay or discharge before they become delinquent (1) all taxes, assessments and governmental charges levied or imposed upon it or any Subsidiary or upon the income, profits or property of WRIT or any Subsidiary, and (2) all lawful claims for labor, materials and supplies that, if unpaid, might by law become a material lien upon the property of WRIT or any Subsidiary.

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But WRIT will not be required to pay or discharge any tax, assessment, charge or claim whose amount, applicability or validity is being contested in good faith. (Section 1007 of each indenture).

Provision of Financial Information. Whether or not WRIT is subject to Section 13 or 15(d) of the Securities Exchange Act, WRIT will be required, within 15 days of each of the dates by which WRIT would have been required to file annual reports, quarterly reports and other documents with the SEC if WRIT were subject to those sections, to

Additional Covenants. The prospectus supplement will describe any additional covenants of WRIT relating to any series of debt securities.

Events of Default, Notice and Waiver

Unless otherwise specified in the applicable prospectus supplement, each of the following is an Event of Default with respect to any series of debt securities issued under either indenture:

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“Significant Subsidiary” means any Subsidiary that meets any of the following:

If an Event of Default occurs and continues under any indenture relating to debt securities of any series at the time outstanding, then the indenture trustee or the holders of 25% or more in principal amount of the outstanding debt securities of that series may declare the principal amount of, and any premium on, all of the debt securities of that series to be due and payable immediately. If the debt securities of that series are original issue discount securities or indexed securities, then only the portion of the principal amount as may be specified in the terms of those securities plus any premium on those securities may be declared due and payable. To declare an acceleration, an indenture trustee must provide written notice to WRIT. If the holders declare an acceleration, they must provide written notice to WRIT and to the indenture trustee.

At any time after a declaration of acceleration relating to debt securities of a series, or of all debt securities then outstanding under the applicable indenture, has been made, but before a judgment or decree for payment of the money due has been obtained by the indenture trustee, the holders of a majority in principal amount of outstanding debt securities of the series, or of all debt securities then outstanding under the applicable indenture, may rescind the declaration and its consequences if:

The holders of a majority in principal amount of the outstanding debt securities of any series, or of all debt securities then outstanding under the applicable indenture, may waive any past default relating to that series and its consequences, except a default (1) in the payment of the principal of or any premium, interest or additional amounts payable on any debt security of that series or (2) relating to a covenant or provision contained in the applicable indenture that cannot be modified or amended without the consent of the holder of each outstanding debt security affected. (Section 513 of each indenture).

Each indenture trustee will be required to give notice to the holders of debt securities within 90 days of a default under the applicable indenture unless the default has been cured or waived. But the indenture trustee may

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withhold notice to the holders of any series of debt securities of any default relating to that series, except a default in the payment of the principal of, any premium, interest or additional amount payable on any debt security of that series or in the payment of any sinking fund installment relating to any security of that series, if specified responsible officers of the indenture trustee consider withholding notice to be in the interest of the holders of that series. (Section 601 of each indenture).

No holder of debt securities of any series may institute any proceeding, judicial or otherwise, relating to the indenture or for any remedy under the indenture, unless the indenture trustee fails to act within 60 days after it has received a written request to institute proceedings relating to a continuing Event of Default from the holders of 25% or more in principal amount of the outstanding debt securities of that series, as well as an offer of indemnity reasonably satisfactory to it. (Section 507 of each indenture). But this provision does not prevent any holder of debt securities from instituting suit to enforce payment of the principal of and any premium, interest and additional amount payable on the debt securities on the due dates of those payments. (Section 508 of each indenture).

Subject to provisions in each indenture relating to the indenture trustee’s duties if a default occurs, each indenture trustee will not be obligated to exercise any of its rights or powers under the applicable indenture at the request or direction of any holders of any series of debt securities then outstanding under the indenture, unless the holders have offered to the indenture trustee reasonable security or indemnity. (Section 602 of each indenture). The holders of a majority in principal amount of the outstanding debt securities of any series, or of all debt securities then outstanding under the applicable indenture, will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the indenture trustee, or of exercising any trust or power conferred upon the indenture trustee. But an indenture trustee may refuse to follow any direction that (1) is in conflict with any law or the indenture, (2) may involve the indenture trustee in personal liability or (3) may be unduly prejudicial to the holders of debt securities of that series not joining in the direction. (Section 512 of each indenture).

Within 120 days after the close of each fiscal year, WRIT will be required to deliver to each indenture trustee a certificate, signed by one of several specified officers of WRIT, stating whether that officer has knowledge of any default under the applicable indenture and, if so, specifying each known default and its nature and status. (Section 1009 of each indenture).

Modification of the Indentures

Each indenture may be modified or amended only with the consent of the holders of a majority in principal amount of all outstanding debt securities affected by the modification or amendment. But no modification or amendment may, without the consent of the holder of each debt security affected by the modification or amendment:

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The holders of a majority in principal amount of outstanding debt securities issued under either indenture may waive compliance by WRIT with specified covenants and conditions in the indenture. (Section 1013 of each indenture).

WRIT and the applicable indenture trustee may modify or amend each indenture without the consent of any holder of debt securities for any of the following purposes:

Each indenture provides that in determining whether the holders of the requisite principal amount of outstanding debt securities of a series have given any request, demand, authorization, direction, notice, consent or waiver under the indenture or whether a quorum is present at a meeting of holders of debt securities,

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Each indenture contains provisions for convening meetings of the holders of debt securities of a series. (Section 1501 of each indenture). A meeting may be called at any time by the applicable indenture trustee, and also, upon request, by WRIT or the holders of at least 10% in principal amount of the outstanding debt securities of that series, if notice is given as provided in the applicable indenture. (Section 1502 of each indenture).

Any resolution presented at a meeting or adjourned meeting properly reconvened at which a quorum is present may be adopted by the affirmative vote of the holders of a majority in principal amount of the outstanding debt securities of that series. But any resolution relating to any request or demand that may be made, notice or consent that may be given, or waiver or action that may be taken by the holders of a specified percentage, which is less than a majority in principal amount of the outstanding debt securities of a series, may be adopted at a meeting or adjourned meeting properly reconvened at which a quorum is present by the affirmative vote of the holders of that specified percentage in principal amount of the outstanding debt securities of that series. The provisions described above in this paragraph do not apply to those situations where modifications or amendments of the applicable indenture require the consent of the holders of each debt security affected. (Section 1504 of each indenture).

Any resolution passed or decision taken at any meeting of holders of debt securities of any series properly held in accordance with the applicable indenture will be binding on all holders of debt securities of that series. The quorum at any meeting called to adopt a resolution, and at any reconvened meeting, will be persons holding or representing a majority in principal amount of the outstanding debt securities of a series. But if any action is to be taken at the meeting relating to a consent or waiver that may be given by the holders of not less than a specified percentage in principal amount of the outstanding debt securities of a series, the persons holding or representing that specified percentage in principal amount of the outstanding debt securities of that series will constitute a quorum (Section 1504 of each indenture).

Despite the foregoing provisions, if any action is to be taken at a meeting of holders of debt securities of any series relating to any request, demand, notice, consent, waiver or other action that the indenture expressly provides may be made, given or taken by the holders of a specified percentage in principal amount of all outstanding debt securities affected by that action, or of the holders of that series and one or more additional series:

Subordination

Upon any distribution to creditors of WRIT in a liquidation, dissolution or reorganization, the payment of the principal of and interest on the subordinated debt securities will be subordinated, to the extent provided in the

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subordinated indenture, to the prior payment in full of all Senior Debt, which we define below. (Sections 1601 and 1602 of the subordinated indenture). But WRIT’s obligation to make payment of the principal and interest on the subordinated debt securities will not otherwise be affected. (Section 1608 of the subordinated indenture). No payment of principal or interest may be made on the subordinated debt securities at any time if a default on Senior Debt exists that permits the holders of the Senior Debt to accelerate its maturity and the default is the subject of judicial proceedings or WRIT receives notice of the default. (Section 1603 of the subordinated indenture). After all Senior Debt is paid in full and until the subordinated debt securities are paid in full, holders will be subrogated to the rights of holders of Senior Debt to the extent that distributions otherwise payable to holders of the subordinated debt have been applied to the payment of Senior Debt. (Section 1607 of the subordinated indenture). By reason of the subordination, if assets are distributed upon insolvency, some general creditors of WRIT may recover more, ratably, than holders of the subordinated debt securities.

“Senior Debt” as defined in the subordinated indenture means the principal of and interest on, or substantially similar payments to be made by WRIT regarding the following, whether outstanding at the date of execution of the subordinated indenture or subsequently incurred, created or assumed:

At June 30, 2006, Senior Debt aggregated approximately $618.7 million in principal amount. The subordinated indenture does not restrict the creation of additional Senior Debt. But the senior indenture contains limitations on WRIT’s incurrence of indebtedness. See “Covenants—Senior Indenture Limitations on Incurrence of Debt.”

Discharge, Defeasance and Covenant Defeasance

Under each indenture, WRIT may discharge obligations to holders of any series of debt securities issued under the indenture that have not already been delivered to the applicable indenture trustee for cancellation and that either have become due and payable or will become due and payable within one year. To do so WRIT must irrevocably deposit in trust with the applicable indenture trustee, funds in currencies, currency units or composite currencies in which those debt securities are payable in an amount sufficient to pay the entire debt on those debt securities including principal, any premium, interest and any additional amounts payable to the date of the deposit, if the debt securities have become due and payable, or, if they have not, to the stated maturity or redemption date. (Section 401 of each indenture).

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Each indenture provides that, if specified provisions of the indenture are made applicable to the debt securities of or within any series, WRIT may elect either:

To elect defeasance or covenant defeasance, WRIT must irrevocably deposit in trust with the applicable indenture trustee, an amount sufficient to pay the principal of, any premium and interest on those debt securities, and any mandatory sinking fund or similar payments, on the scheduled due dates. The amount deposited may be in currencies, currency units or composite currencies in which those debt securities are payable at stated maturity, or Government Obligations, which we define below, or both. But the scheduled payment of principal and interest on any Government Obligations deposited must be before the scheduled due date of the principal of, any premium and interest on the debt securities. (Section 1404 of each indenture).

“Government Obligations” means securities that are:

A defeasance trust or covenant defeasance trust may be established only if WRIT has delivered to the applicable indenture trustee an opinion of counsel, as specified in each indenture, to the effect that the holders of the defeased debt securities will not recognize income, gain or loss for United States federal income tax purposes as a result of the defeasance or covenant defeasance and will be subject to United States federal income tax on the same amounts, in the same manner and at the same times as would have been the case if the defeasance or covenant defeasance had not occurred. In the case of defeasance, the opinion of counsel must also refer to and be based upon a ruling of the Internal Revenue Service or a change in applicable United States federal income tax law occurring after the date of the indenture. (Section 1404 of each indenture).

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Unless otherwise described in the applicable prospectus supplement, if after WRIT has deposited funds or Government Obligations or both to effect defeasance or covenant defeasance relating to debt securities of any series, (1) the holder of a debt security of the series is entitled to, and does, under specified provisions of the indenture or the terms of the debt security, elect to receive payment in a currency, currency unit or composite currency other than that in which the deposit has been made, or (2) a Conversion Event, which we define below, occurs in regard to the currency, currency unit or composite currency in which the deposit has been made, the debt represented by the debt security will be treated as fully discharged and satisfied through the payment of the principal of, any premium, and interest on the debt security as they become due out of the proceeds yielded by converting the amount so deposited into the currency, currency unit or composite currency in which the debt security becomes payable as a result of the election or the Conversion Event based on the applicable market exchange rate. (Section 1405 of each indenture).

“Conversion Event” means the ceasing the use of:

Unless otherwise indicated in the applicable prospectus supplement, all payments of principal of, any premium, and interest on any debt security that is payable in a foreign currency that ceases to be used by its government of issuance will be in U.S. dollars.

If WRIT effects covenant defeasance relating to any debt securities and the debt securities are declared due and payable because an Event of Default occurs, there is a risk that the amount in the currency, currency unit or composite currency in which the debt securities are payable, and Government Obligations on deposit with the applicable indenture trustee, though sufficient to pay amounts due on the debt securities at the time of their stated maturity, may not be sufficient to pay amounts due on the debt securities at the time of the acceleration resulting from the Event of Default. But WRIT would remain liable to make payment of the amounts due at the time of acceleration.

The applicable prospectus supplement may further describe any provisions, permitting defeasance or covenant defeasance, including any modifications to the provisions described above, relating to the debt securities of or within a particular series.

Conversion rights

If the debt securities are convertible into common shares or preferred shares, the applicable prospectus supplement will describe the terms and conditions of conversion. The terms will include:

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Global securities

The debt securities of a series may be issued in whole or in part in the form of one or more global securities that will be deposited with, or on behalf of, a depositary identified in the applicable prospectus supplement relating to that series. Global securities may be issued in either registered or bearer form and in either temporary or permanent form. The applicable prospectus supplement will describe the specific terms of the depositary arrangement relating to that series of debt securities.

PLAN OF DISTRIBUTION

We may sell the offered securities to one or more underwriters for public offering and sale by them or may sell the offered securities to investors directly or through agents, which agents may be affiliated with us. Direct sales to investors may be accomplished through subscription offerings or through subscription rights distributed to our shareholders. In connection with subscription offerings or the distribution of subscription rights to shareholders, if all of the underlying offered securities are not subscribed for, we may sell such unsubscribed offered securities to third parties directly or through agents and, in addition, whether or not all of the underlying offered securities are subscribed for, we may concurrently offer additional offered securities to third parties directly or through agents, which agents may be affiliated with us. Any underwriter or agent involved in the offer and sale of the offered securities will be named in the applicable prospectus supplement.

The distribution of the offered securities may be effected from time to time in one or more transactions at a fixed price or prices, which may be changed, or at prices related to the prevailing market prices at the time of sale, such as an “at the market offering,” or at negotiated prices, any of which may represent a discount from the prevailing market price. We also may, from time to time, authorize underwriters acting as our agents to offer and sell the offered securities upon the terms and conditions set forth in the applicable prospectus supplement. In connection with the sale of offered securities, underwriters may be deemed to have received compensation from us in the form of underwriting discounts or commissions and may also receive commissions from purchasers of offered securities for whom they may act as agent. Underwriters may sell offered securities to or through dealers, and such dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for whom they may act as agent.

Any underwriting compensation paid by us to underwriters or agents in connection with the offering of offered securities, and any discounts, concessions or commissions allowed by underwriters to participating dealers, will be set forth in the applicable prospectus supplement. Underwriters, dealers and agents participating in the distribution of the offered securities may be deemed to be underwriters, and any discounts and commissions received by them and any profit realized by them on resale of the offered securities may be deemed to be underwriting discounts and commissions, under the Securities Act. Underwriters, dealers and agents may be entitled, under agreements entered into with us, to indemnification against and contribution toward civil liabilities, including liabilities under the Securities Act. Any such indemnification agreements will be described in the applicable prospectus supplement.

If so indicated in the applicable prospectus supplement, we will authorize dealers acting as our agents to solicit offers by institutions to purchase offered securities from us at the public offering price set forth in such prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on the date or dates stated in such prospectus supplement. Each contract will be for an amount not less than, and the aggregate principal amount of offered securities sold pursuant to contracts shall be not less nor more than, the respective amounts stated in the applicable prospectus supplement. Institutions with whom contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions, and other institutions but will in all cases be subject to our approval.

Contracts will not be subject to any conditions except the purchase by an institution of the offered securities covered by its contracts shall not at the time of delivery be prohibited under the laws of any jurisdiction in the

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United States to which such institution is subject, and if the offered securities are being sold to underwriters, we shall have sold to such underwriters the total principal amount of the offered securities less the principal amount of the securities covered by contracts. Some of the underwriters and their affiliates may be customers of, engage in transactions with and perform services for us and our subsidiaries in the ordinary course of business.

Unless otherwise indicated in the applicable prospectus supplement, any securities issued under this prospectus will be new issues of securities with no established market. Any underwriters or agents to or through whom the securities are sold by us for public offering and sale may make a market in the securities, but the underwriters or agents will not be obligated to do so and may discontinue any market making at any time without notice. We do not know how liquid the trading market for any of our securities will be.

LEGAL OPINIONS

The validity of the offered securities is being passed upon for WRIT by Arent Fox PLLC, Washington, D.C. David M. Osnos, a trustee of WRIT, is of counsel to Arent Fox PLLC. The validity of the offered securities will be passed upon for any underwriters by the counsel named in the applicable prospectus supplement.

EXPERTS

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements and schedule included in our Annual Report on Form 10-K for the year ended December 31, 2005, and management’s assessment of the effectiveness of our internal control over financial reporting as of December 31, 2005, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements and schedule and management’s assessment are incorporated by reference in reliance on Ernst & Young LLP’s reports, given on their authority as experts in accounting and auditing.

The historical summaries of gross income and direct operating expenses of (i) Prosperity Medical Center for the year ended December 31, 2002, (ii) Albemarle Point for the year ended December 31, 2004 and (iii) Alexandria Professional Center, 9707 Medical Center Drive, 15001 Shady Grove Road, Randolph Shopping Center, Montrose Shopping Center and Plumtree Medical Center for the year ended December 31, 2005, are incorporated in reliance on the reports dated December 2, 2003, August 10, 2005 and June 23, 2006, respectively, of Argy, Wiltse & Robinson, P.C., which we also incorporate by reference, and on the authority of that firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public at the SEC’s website at http://www.sec.gov. You may also read and copy any document we file at the SEC’s Public Reference Room at 100 F Street, N.E. Washington, D.C. 20549. Please call the SEC at 1-(800) SEC-0330 for further information on the operating rules and procedures for the public reference room.

Because our common shares are listed on the New York Stock Exchange, you also may read our reports, proxy statements and other information at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005.

We have filed with the SEC a registration statement relating to the offered securities on Form S-3 under the Securities Act of 1933. This prospectus does not contain all the information in the registration statement. We have omitted parts of it in accordance with the SEC’s rules and regulations. For further information, you should refer to the registration statement including its exhibits and amendments.

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The SEC permits us to incorporate by reference in this prospectus some information that is contained in other documents we file with the SEC. This means that we may disclose important information by referring you to other documents that contain the information, including documents that we file after the date of this prospectus. The information that is incorporated by reference is considered to be part of this prospectus.

We incorporate by reference the documents listed below:

Information in this prospectus may add to, update or change information in a previously filed document incorporated by reference in this prospectus. In that case, you should rely on the information in this prospectus. Information in a document filed after the date of this prospectus may add to, update or change information in this prospectus or in a previously filed document incorporated by reference in this prospectus. In that case, you should rely on the information in the later filed document.

You may request a copy of these filings and any amendments thereto at no cost, by writing or telephoning us. Those copies will not include exhibits to those documents unless the exhibits are specifically incorporated by reference in the documents or unless you specifically request them. Please direct your request to:

Investor Relations, Washington REIT, 6110 Executive Boulevard, Suite 800, Rockville, Maryland 20852, (301) 984-9400.

We maintain a website at www.writ.com. Statements made in our website are not part of this prospectus.

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1,600,000 Common Shares of Beneficial Interest

Prospectus Supplement

June 1, 2007

Robert W. Baird & Co.