COPT Defense Properties Annual report pursuant to Section 13 and 15(d)

Concentration of Rental Revenue (Tables)

12 Months Ended

Dec. 31, 2011

	For the Years Ended December 31,

	2011			2010			2009
United States Government		17	%		16	%		15	%
Northrop Grumman Corporation(1)		8	%		9	%		8	%
Booz Allen Hamilton, Inc.		6	%		5	%		6	%
Five largest tenants		38	%		35	%		34	%

(1): Includes affiliated organizations and agencies and predecessor companies.

Tabular disclosure of the nature of a concentration, a benchmark to which it is compared, and the percentage that the risk is to the benchmark.