COPT Announces Offering of 4,000,000 Common Shares

Corporate Office Properties Trust (COPT) (NYSE: OFC) announced today that it plans to sell 4,000,000 newly issued common shares in an underwritten public offering pursuant to its effective shelf registration statement previously filed with the Securities and Exchange Commission.

The underwriters for the offering will be granted a 30-day option to purchase up to an additional 600,000 shares to cover over-allotments, if any.

The joint book-running managers for this offering are Wells Fargo Securities, RBC Capital Markets, and KeyBanc Capital Markets.

The Company intends to use the net proceeds from the offering to repay amounts outstanding under its unsecured revolving credit facility and for general corporate purposes.

Copies of the preliminary prospectus supplement relating to these securities may be obtained from Wells Fargo Securities, Equity Syndicate Department, 375 Park Avenue, New York, New York 10152, or by calling 800-326-5897 or by email at cmclientsupport@wellsfargo.com; from RBC Capital Markets, Attention: Prospectus Department, Three World Financial Center, 200 Vesey Street, 8th Floor, New York, NY 10281, or by calling (877) 822-4089; and from KeyBanc Capital Markets, Attention: Prospectus Delivery Department, 127 Public Square, 6th Floor, Cleveland, OH 44114, or by calling (216) 689-0421.

This announcement shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or other jurisdiction.

Company Information

COPT is a specialty office real estate investment trust (REIT) that focuses primarily on strategic customer relationships and specialized tenant requirements in the U.S. Government and Defense Information Technology sectors and Data Centers serving such sectors. The Company acquires, develops, manages and leases office and data center properties that are typically concentrated in large office parks primarily located adjacent to government demand drivers and/or in strong markets that we believe possess growth opportunities. As of March 31, 2011, the Company owned 272 office properties totaling 21.3 million rentable square feet, which includes 20 properties totaling 1.1 million square feet held through joint ventures. The Company’s portfolio primarily consists of technically sophisticated buildings in visually appealing settings that are environmentally sensitive, sustainable and meet unique customer requirements. COPT is an S&P MidCap 400 company and more information can be found at www.copt.com.

Forward-Looking Information

This press release may contain "forward-looking” statements, as defined in Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, that are based on the Company’s current expectations, estimates and projections about future events and financial trends affecting the Company. Forward-looking statements can be identified by the use of words such as "may,” "will,” "should,” "could,” "believe,” "anticipate,” "expect,” "estimate,” "plan” or other comparable terminology. Forward-looking statements are inherently subject to risks and uncertainties, many of which the Company cannot predict with accuracy and some of which the Company might not even anticipate. Accordingly, the Company can give no assurance that these expectations, estimates and projections will be achieved. Future events and actual results may differ materially from those discussed in the forward-looking statements.

Important factors that may affect these expectations, estimates, and projections include, but are not limited to:

• general economic and business conditions, which will, among other things, affect office property demand and rents, tenant creditworthiness, interest rates and financing availability;
• adverse changes in the real estate markets including, among other things, increased competition with other companies;
• the Company’s ability to borrow on favorable terms;
• risks of real estate acquisition and development activities, including, among other things, risks that development projects may not be completed on schedule, that tenants may not take occupancy or pay rent or that development or operating costs may be greater than anticipated;
• risks of investing through joint venture structures, including risks that the Company’s joint venture partners may not fulfill their financial obligations as investors or may take actions that are inconsistent with the Company’s objectives;
• changes in our plans for properties or views of market economic conditions or failure to obtain development rights, either of which could result in recognition of impairment losses;
• our ability to satisfy and operate effectively under Federal income tax rules relating to real estate investment trusts and partnerships;
• governmental actions and initiatives, including risks associated with the impact of a government shutdown such as a reduction in rental revenues and non-renewal of leases;
• the dilutive effects of issuing additional common shares; and
• environmental requirements.

The Company undertakes no obligation to update or supplement any forward-looking statements. For further information, please refer to the Company’s filings with the Securities and Exchange Commission, particularly the section entitled "Risk Factors” in Item 1A of the Company’s Annual Report on Form 10-K for the year ended December 31, 2010.