Corporate Office Properties Trust Signs 125,681 Square Foot Lease at the National Business Park.

COLUMBIA, Md. -- Corporate Office Properties Trust (NYSE: OFC) announced today the execution of a long-term lease with a large credit worthy tenant for the entire building to be located at 318 Carina Road, Annapolis Junction, Maryland. The building, to be known as 318 NBP, will be a 125,681 square foot Class A office building and is one of four buildings under construction in Phase II of The National Business Park (NBP).

Phase II at NBP when complete, will consist of 10 buildings totaling 1.3 million square feet. Including 318 NBP, Corporate Office Properties Trust has 677,709 square feet under construction in Phase I and Phase II at NBP. 318 NBP has a planned occupancy of fourth quarter 2005.

"This is another full building lease in a long line of leases at NBP demonstrating its high demand and our continued ability to deliver superior real estate solutions," stated Randall M. Griffin, President and Chief Operating Officer for Corporate Office Properties Trust.

Company Information

Corporate Office Properties Trust is a fully integrated, self-managed, real estate investment trust which focuses on the ownership, management, leasing, acquisition and development of suburban office properties located in select Mid-Atlantic submarkets. The Company also pursues selective expansion outside of our core markets to meet anticipated current tenant demand. The Company currently owns 145 office properties totaling 12.0 million rentable square feet, including two properties held through joint ventures. Corporate Development Services provides a wide range of development and construction management services. In addition, Corporate Office Services provides land planning, design/build services, consulting and merchant development to third party entities. The Company's shares are traded on the New York Stock Exchange under the symbol OFC. More information on Corporate Office Properties Trust can be found on the Internet 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", "expect", "estimate" 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:

--the Company's ability to borrow on favorable terms;

--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;

--risk of real estate acquisition and development, 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;

--governmental actions and initiatives; 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 1 of the Company's Annual Report on Form 10-K for the year ended December 31, 2003.