Exhibit 12.1

Corporate Office Properties Trust

Ratio of Earnings to Combined Fixed Charges and Preferred Share Dividends
(Dollars in thousands)

	Years Ended December 31,
Earnings:	2006			2005			2004			2003			2002
Income from continuing operations before equity in loss of unconsolidated entities, income taxes and minority interests	$	39,681		$	40,083		$	42,074		$	33,317		$	24,798
Gain (loss) on sales of real estate, excluding discontinued operations	889			366			(150		)	472			2,564
Combined fixed charges and preferred share dividends (from below)	110,541			85,240			70,627			71,541			57,894
Amortization of capitalized interest	527			337			285			254			195
Distributed income (loss) of equity investees	26			(164		)	(83		)	(181		)	295
Subtract:
Capitalized interest (from below)	(14,559		)	(9,871		)	(5,112		)	(2,846		)	(3,091		)
Preferred share dividends included in fixed charges	(15,404		)	(14,615		)	(16,329		)	(12,003		)	(10,134		)
Preferred unit distributions included in fixed charges	(660		)	(660		)	(179		)	(1,049		)	(2,287		)
Repurchase of preferred units in excess of recorded book value	—			—			—			(11,224		)	—
Issuance costs associated with redeemed preferred shares	(3,896		)	—			(1,813		)	—			—
Total earnings	$	117,145		$	100,716		$	89,320		$	78,281		$	70,234
Combined fixed charges and preferred share dividends:
Interest expense on continuing operations	$	71,378		$	54,872		$	42,148		$	38,730		$	36,501
Interest expense on discontinued operations	1,042			2,272			2,115			2,449			2,855
Capitalized interest (internal and external)	14,559			9,871			5,112			2,846			3,091
Amortization of debt issuance costs on continuing operations-expensed	2,847			2,229			2,420			2,756			2,490
Amortization of debt issuance costs on discontinued operations-expensed	134			11			11			11			11
Amortization of debt issuance costs-capitalized	237			272			113			—			59
Interest included in rental expense	384			438			387			473			466
Preferred share dividends	15,404			14,615			16,329			12,003			10,134
Preferred unit distributions	660			660			179			1,049			2,287
Repurchase of preferred units in excess of recorded book value	—			—			—			11,224			—
Issuance costs associated with redeemed preferred shares	3,896			—			1,813			—			—
Total combined fixed charges and preferred share dividends	$	110,541		$	85,240		$	70,627		$	71,541		$	57,894
Ratio of earnings to combined fixed charges and preferred share dividends	1.06			1.18			1.26			1.09			1.21