Supplemental Information

(Unaudited)

December 31, 2010

Corporate Office Properties Trust

Index to Supplemental Information (Unaudited)

December 31, 2010

	Page
Highlights and Discussion
Reporting Period Highlights — Periods Ended December 31, 2010	1
Forward-Looking Statements	4
Financial Statements
Selected Financial Summary Data	5
Quarterly Consolidated Balance Sheets	6
Consolidated Statements of Operations	7
Consolidated Reconciliations of Funds From Operations (FFO), Adjusted FFO (AFFO), Earnings Per Share (EPS)	8
Consolidated Reconciliations of Earnings Before Interest, Income Taxes, Depreciation and Amortization (EBITDA), Net Operating Income (NOI), Discontinued Operations, Gains on Sales of Real Estate and Certain Non-GAAP Measures	9
Reconciliations of Non-GAAP Measurements	10
Selected Financial Analyses
Real Estate Revenues from Continuing and Discontinued Operations and NOI by Geographic Region	11
Same Office Property Cash and GAAP NOI	12
Operating Ratios	13
Debt Analysis	14
Debt Maturity Schedule — December 31, 2010	15
Quarterly Equity Analysis	16
Dividend Analysis	17
Investor Composition and Analyst Coverage	18
Portfolio Summary
Property Summary by Region — December 31, 2010 — Wholly Owned Office Properties	19
Property Summary by Region — December 31, 2010 — Joint Venture Office Properties	25
Property Occupancy Rates by Region by Quarter — Wholly Owned Office Properties	26
Property Occupancy Rates by Region by Quarter — Joint Venture Office Properties	27
Top Twenty Tenants of Wholly Owned Office Properties as of December 31, 2010	28
Average Occupancy Rates by Region for Same Office Properties	29
Lease Expiration Analysis by Year for Wholly Owned Operating Office Properties	30
Renewal Analysis for Wholly Owned Office Properties for Periods Ended December 31, 2010	31
Office Property Development Summary as of December 31, 2010	32
Office Property Construction Placed into Service as of December 31, 2010	34
Office Property Construction Leasing as of December 31, 2010	35
Land Controlled as of December 31, 2010	36
Wholesale Data Center Summary as of December 31, 2010	37
Real Estate Joint Venture Summary as of December 31, 2010	38

To Members of the Investment Community:

We prepared this supplemental information package to provide you with additional detail on our properties and operations.  The information in this package is unaudited, furnished to the Securities and Exchange Commission (“SEC”) and should be read in conjunction with our quarterly and annual reports.  If you have any questions or comments, please contact Stephanie Krewson, Vice President, Investor Relations at (443) 285-5453 or stephanie.krewson@copt.com.  Reconciliations between GAAP and non-GAAP measurements have been provided.  Refer to our Form 8-K for definitions of certain terms used herein.

Corporate Office Properties Trust (COPT) (NYSE: OFC) 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.  More information on COPT can be found at www.copt.com.

Reporting Period Highlights — Year Ended December 31, 2010

Financial Results

·FFO, excluding the effect of $3.4 million in operating property acquisition costs ($0.06 per diluted share), was $171.7 million, or $2.36 per diluted share, for the year ended December 31, 2010 as compared to $173.3 million, or $2.49 per diluted share, for the year ended December 31, 2009, representing a decrease of 5% per share.  FFO was $168.3 million, or $2.30 per diluted share, for the year ended December 31, 2010.  The decrease in FFO was due primarily to a $19.7 million increase in interest expense, an $8.0 million decrease in NOI from same office properties and a $5.4 million decrease in NOI from three properties that we expect to redevelop, including two properties in Greater Philadelphia.  These decreases were partially offset by NOI from acquired properties and development placed in service and gains recognized on our investment in The KEYW Holding Corporation.

·Net income attributable to COPT common shareholders was $26.7 million, or $0.43 per diluted share, for the year ended December 31, 2010 as compared to $40.2 million, or $0.70 per diluted share, for the year ended December 31, 2009, a decrease of 39% per share.

·Diluted AFFO available to common share and common unit holders was $112.7 million for the year ended December 31, 2010 as compared to $119.8 million for the year ended December 31, 2009, a decrease of 6%.

·Our diluted FFO payout ratio, excluding the effect of operating property acquisition costs, was 70% for the year ended December 31, 2010 as compared to 62% for the year ended December 31, 2009.  Our diluted AFFO payout ratio was 94% for the year ended December 31, 2010 as compared to 80% for the year ended December 31, 2009.

Acquisitions / Dispositions

·In 2010, we completed the following acquisitions totaling $317 million:

·1550 Westbranch Drive, a 152,000 square feet office property in McLean, Virginia that is 100% leased to The MITRE Corporation, for $40.0 million on June 28, 2010.

·9651 Hornbaker Road, a 233,000 square foot wholesale data center known as Power Loft @ Innovation in Manassas, Virginia, for $115.5 million on September 14, 2010.  Rents for this property are based on the amount of megawatts of power made available for the exclusive use of tenants in the property (referred to as critical load).  This property, the shell of which was completed in early 2010, was 17% leased on the date of acquisition to two tenants that have a combined initial critical load of three megawatts and further expansion rights of up to a combined five megawatts.  We expect to complete the development of the property to an initial stabilization critical load of 18 megawatts for additional development costs initially estimated at $166 million.  Full critical load of the property is expected to be up to 30 megawatts.

·Two office properties totaling 362,000 square feet at 1201 M Street SE and 1220 12th Street SE (known as Maritime Plaza I and II) in the Capitol Riverfront submarket of Washington, DC that were 100% leased on September 28, 2010 for approximately $119 million, including the assumption of a $70.1 million mortgage loan having a fair value of $73.3 million with a fixed interest rate of 5.35% that matures in March 2014.  The buildings are subject to ground leases that expire in 2099 and 2100.

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·3120 Fairview Park Drive, a 183,000 square foot, shell-complete, office property in Falls Church, Virginia that was 4% leased, for $43.0 million on November 23, 2010.

·On September 8, 2010, we sold two office properties in Dayton, New Jersey totaling 201,000 square feet for $20.9 million and recognized a gain of $780,000.  We also on September 8, 2010 sold a land parcel that was contiguous to these properties for $3.0 million and recognized a gain of $2.5 million.

Development Activities

·We entered two new submarkets by:

·Completing the formation of LW Redstone Company, LLC, a joint venture created to develop Redstone Gateway, a 468 acre land parcel adjacent to Redstone Arsenal in Huntsville, Alabama.  The land is owned by the U.S. Government and is under a long term master lease to the joint venture through the Enhanced Use Lease program.  Through this master lease, we will work closely with Redstone Arsenal to create a business park that we expect will total approximately 4.6 million square feet of office and retail space when completed, including approximately 4.4 million square feet of Class A office space.  In addition, the business park will include hotel and other amenities.  We are the managing partner of the joint venture with a controlling interest and responsibility for development, leasing and management of the office space at the business park.  Development and construction of the business park is expected to take place over a 15 to 20 year period.

·Acquiring 15 acres on which we are entitled to develop up to 978,000 square feet in Springfield, Virginia.  The property, which is known as Patriot Ridge, is located adjacent to the new 2.4 million square foot National Geospatial Intelligence Agency (NGA) headquarters currently under construction at Fort Belvoir, a government demand driver that we expect to benefit as a result of mandates by the Base Realignment and Closure Commission.

·We placed into service an aggregate of 816,000 square feet in newly-constructed space in nine properties during the year ended December 31, 2010.  These properties were 77% leased as of December 31, 2010.

·We completed leasing on an aggregate of 808,000 square feet in newly-constructed space during the year ended December 31, 2010.

Operations

·Same office cash NOI for the year ended December 31, 2010, excluding gross lease termination fees, decreased by $3.1 million, or 1%, as compared to the year ended December 31, 2009.  Including gross lease termination fees, our same office property cash NOI decreased by $5.0 million, or 2%, as compared to the year ended December 31, 2009.  Our same office portfolio consists of 230 properties and represents 85% of the rentable square footage of our consolidated office properties as of December 31, 2010.

·We renewed 2.5 million square feet in the year ended December 31, 2010 with an average committed cost of $7.84 per square foot.  For our renewed space during the year ended December 31, 2010, we realized an increase of 3% in total rent, as measured from the GAAP straight-line rent in effect preceding the renewal date, and a decrease of 5% in total cash rent.  For our renewed and retenanted space of 3.2 million square feet during the year ended December 31, 2010, we realized an increase of 2% in total rent, as measured from the GAAP straight-line rent in effect preceding the renewal date, and a decrease of 6% in total cash rent.  The average committed cost for our space renewed and retenanted during the year ended December 31, 2010 totaled $11.72 per square foot.

·We recognized $3.4 million in lease termination fees for the year ended December 31, 2010, net of write-offs of related straight-line rents and intangible assets and liabilities, as compared to $4.6 million in the year ended December 31, 2009.

Financing Activity and Capital Transactions

·On April 7, 2010, we issued $240.0 million aggregate principal amount of 4.25% Exchangeable Senior Notes due 2030.  The notes have an exchange settlement feature that provides that the notes may, under certain circumstances, be exchangeable for cash and our common shares at an initial exchange rate (subject to adjustment) of 20.7658 shares per $1,000 principal amount of the notes (equivalent to an exchange price of $48.16 per common share, a 20% premium over the closing price on the NYSE on the transaction pricing date).  On or after April 20, 2015, we may redeem the notes in cash, in whole or in part.  The holders of the notes have the right to require us to repurchase the notes in cash, in whole or in part, on each of April 15, 2015, April 15, 2020 and April 15, 2025, or in the event of a “fundamental change,” as defined under the terms of the notes.  We used the proceeds for general corporate purposes, including repayment of borrowings under our Revolving Credit Facility.

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·On November 5, 2010, we issued 7.5 million common shares at a public offering price of $34.25 per share for net proceeds of $245.8 million after underwriting discounts but before offering expenses.  The net proceeds were used to pay down our Revolving Credit Facility and for general corporate purposes.

·During 2010, we increased the borrowing capacity under our Revolving Credit Facility by $200.0 million, from $600.0 million to $800.0 million.

·For the year ended December 31, 2010, we achieved an EBITDA interest coverage ratio of 3.01x and an EBITDA fixed charge coverage ratio of 2.54x.

Reporting Period Highlights — Quarter Ended December 31, 2010

Financial Results

·FFO, excluding the effect of $470,000 in operating property acquisition costs ($0.01 per diluted share), was $52.7 million, or $0.70 per diluted share, for the quarter ended December 31, 2010 as compared to $39.1 million, or $0.55 per diluted share, for the quarter ended December 31, 2009, representing an increase of 27% per share.  Including these costs, FFO was $52.2 million, or $0.69 per diluted share, for the quarter ended December 31, 2010.  The increase in FFO was due primarily to NOI from acquired properties and development placed in service and gains recognized on our investment in The KEYW Holding Corporation.

·Net income attributable to COPT common shareholders was $11.5 million, or $0.18 per diluted share, for the quarter ended December 31, 2010 as compared to $5.1 million, or $0.08 per diluted share, for the quarter ended December 31, 2009, an increase of 125% per share.

·Diluted AFFO available to common share and common unit holders was $31.0 million for the quarter ended December 31, 2010 as compared to $22.4 million for the quarter ended December 31, 2009, an increase of 38%.

·Our diluted FFO payout ratio, excluding the effect of operating property acquisition costs, was 62% for the quarter ended December 31, 2010 as compared to 72% for the quarter ended December 31, 2009.  Our diluted AFFO payout ratio was 95% for the quarter ended December 31, 2010 as compared to 111% for the quarter ended December 31, 2009.

Operations

·Our wholly owned office property portfolio was 88.2% occupied and 89.5% leased as of December 31, 2010.  Our entire office property portfolio was 87.2% occupied and 88.5% leased as of December 31, 2010.

·The weighted average remaining lease term of our wholly owned office portfolio was 4.9 years as of December 31, 2010, with an average contractual rental rate (including tenant reimbursements of operating costs) of $25.56 per square foot.

·Same office property cash NOI for the quarter ended December 31, 2010, excluding gross lease termination fees, decreased by $1.7 million, or 3%, as compared to the quarter ended December 31, 2009.  Including gross lease termination fees, our same office property cash NOI was flat as compared to the quarter ended December 31, 2009.

·We renewed 1.1 million square feet in the quarter ended December 31, 2010 with an average committed cost of $8.13 per square foot.  For our renewed space during the quarter ended December 31, 2010, we realized an increase of 3% in total rent, as measured from the GAAP straight-line rent in effect preceding the renewal date, and a decrease of 5% in total cash rent.  For our renewed and retenanted space of 1.5 million square feet during the quarter ended December 31, 2010, we realized an increase of 4% in total rent, as measured from the GAAP straight-line rent in effect preceding the renewal date, and a decrease of 4% in total cash rent.  The average committed cost for our space renewed and retenanted during the quarter ended December 31, 2010 totaled $14.02 per square foot.

·We recognized $2.0 million in lease termination fees for the quarter ended December 31, 2010, net of write-offs of related straight-line rents and intangible assets and liabilities, as compared to $236,000 in the quarter ended December 31, 2009.

Financing Activity and Capital Transactions

·As of December 31, 2010, our ratio of debt to total market capitalization was 46% and our ratio of debt to undepreciated book value of real estate assets was 57%.

·For the quarter ended December 31, 2010, we achieved an EBITDA interest coverage ratio of 3.36x and an EBITDA fixed charge coverage ratio of 2.86x.

·For the quarter ended December 31, 2010, our debt to EBITDA ratio was 7.29x and our adjusted debt to EBITDA ratio (excluding construction in progress) was 6.08x.

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·As of December 31, 2010, 78% of our debt had fixed interest rates, including the effect of interest rate swaps in effect.

Forward-Looking Statements

This supplemental information contains “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 our current expectations, estimates and projections about future events and financial trends affecting us.  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 we cannot predict with accuracy and some of which we might not even anticipate.  Accordingly, we 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;

·our ability to borrow on favorable terms;

·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 our joint venture partners may not fulfill their financial obligations as investors or may take actions that are inconsistent with our objectives;

·changes in our plans 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; and

·environmental requirements.

We undertake no obligation to update or supplement any forward-looking statements.  For further information, please refer to our filings with the Securities and Exchange Commission, particularly the section entitled “Risk Factors” in Item 1A of our Annual Report on Form 10-K for the year ended December 31, 2009.

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Selected Financial Summary Data

(dollars in thousands, except per share data)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Real estate revenues from continuing operations	$	123,765		$	114,550		$	109,257		$	112,228		$	108,737		$	459,800		$	423,984
Total revenues from continuing operations	$	151,402		$	128,158		$	135,322		$	149,593		$	178,290		$	564,475		$	767,071
NOI	$	76,694		$	70,724		$	69,847		$	64,700		$	66,822		$	281,965		$	269,449
EBITDA	$	79,652		$	66,976		$	65,259		$	61,683		$	61,056		$	273,570		$	255,726
Net income	$	16,752		$	8,926		$	9,151		$	10,675		$	9,546		$	45,504		$	61,299
Net income attributable to noncontrolling interests	(1,228		)	(94		)	(685		)	(737		)	(458		)	(2,744		)	(4,970		)
Preferred share dividends	(4,026		)	(4,025		)	(4,026		)	(4,025		)	(4,026		)	(16,102		)	(16,102		)
Net income attributable to COPT common shareholders	$	11,498		$	4,807		$	4,440		$	5,913		$	5,062		$	26,658		$	40,227
Diluted EPS	$	0.18		$	0.08		$	0.07		$	0.10		$	0.08		$	0.43		$	0.70
FFO	$	52,222		$	39,053		$	38,870		$	38,156		$	37,180		$	168,301		$	171,325
FFO, excluding operating property acquisition costs	$	52,692		$	41,717		$	39,141		$	38,175		$	39,147		$	171,725		$	173,292
Basic and diluted FFO available to common share and common unit holders	$	47,227		$	34,278		$	33,880		$	33,260		$	32,586		$	148,645		$	152,626
Diluted FFO per share	$	0.69		$	0.54		$	0.53		$	0.53		$	0.52		$	2.30		$	2.46
Diluted FFO per share, excluding operating property acquisition costs	$	0.70		$	0.58		$	0.54		$	0.53		$	0.55		$	2.36		$	2.49
Diluted AFFO available to common share and common unit holders	$	30,962		$	29,498		$	26,992		$	25,234		$	22,422		$	112,686		$	119,837
Payout ratios:
Diluted FFO payout ratio, excluding operating property acquisition costs	61.7		%	71.3		%	73.2		%	75.2		%	72.0		%	69.6		%	61.8		%
Diluted AFFO payout ratio	95.0		%	89.3		%	92.6		%	99.2		%	110.9		%	93.9		%	79.7		%
Total dividends/distributions	$	33,604		$	30,518		$	29,199		$	29,217		$	29,063		$	122,538		$	112,320

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Quarterly Consolidated Balance Sheets

(dollars in thousands)

	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09
Assets
Properties, net
Operating properties	$	3,305,805		$	3,241,507		$	3,040,414		$	2,954,575		$	2,950,327
Land - development	256,487			241,937			234,662			236,350			231,809
Construction in progress	386,195			344,924			319,846			317,283			270,376
Less: accumulated depreciation	(503,032		)	(479,218		)	(464,408		)	(443,246		)	(422,612		)
Total properties, net	3,445,455			3,349,150			3,130,514			3,064,962			3,029,900
Cash and cash equivalents	10,102			11,733			9,879			10,180			8,262
Restricted cash and marketable securities	22,582			21,095			20,738			18,981			16,549
Accounts receivable, net	18,938			18,906			12,552			13,982			17,459
Deferred rent receivable	79,160			76,833			75,683			74,113			71,805
Intangible assets on real estate acquisitions, net	113,735			123,307			96,151			94,925			100,671
Deferred leasing and financing costs, net	60,649			56,568			55,762			50,974			51,570
Prepaid expenses and other assets	93,896			79,780			66,004			70,235			83,806
Total assets	$	3,844,517		$	3,737,372		$	3,467,283		$	3,398,352		$	3,380,022
Liabilities and equity
Liabilities:
Debt, net	$	2,323,681		$	2,468,419		$	2,182,375		$	2,107,131		$	2,053,841
Accounts payable and accrued expenses	99,699			88,461			84,164			86,650			116,455
Rents received in advance and security deposits	31,603			26,919			28,328			32,575			32,177
Dividends and distributions payable	32,986			29,899			28,580			28,556			28,440
Deferred revenue associated with operating leases	14,802			15,790			12,929			13,827			14,938
Distributions received in excess of investment in unconsolidated real estate joint venture	5,545			5,458			5,351			5,238			5,088
Other liabilities	13,063			12,698			13,990			13,836			8,451
Total liabilities	2,521,379			2,647,644			2,355,717			2,287,813			2,259,390
Commitments and contingencies	—			—			—			—			—
Equity:
COPT’s shareholders’ equity:
Preferred shares (aggregate liquidation preference of $216,333)	81			81			81			81			81
Common shares	669			594			593			589			583
Additional paid-in capital	1,511,844			1,271,363			1,269,142			1,244,046			1,238,704
Cumulative distributions in excess of net income	(281,794		)	(265,695		)	(246,008		)	(227,189		)	(209,941		)
Accumulated other comprehensive loss	(4,163		)	(4,861		)	(4,263		)	(3,278		)	(1,907		)
Total COPT’s shareholders’ equity	1,226,637			1,001,482			1,019,545			1,014,249			1,027,520
Noncontrolling interests in subsidiaries
Common units in the Operating Partnership	69,337			61,867			63,675			68,113			73,892
Preferred units in the Operating Partnership	8,800			8,800			8,800			8,800			8,800
Other consolidated entities	18,364			17,579			19,546			19,377			10,420
Total noncontrolling interests in subsidiaries	96,501			88,246			92,021			96,290			93,112
Total equity	1,323,138			1,089,728			1,111,566			1,110,539			1,120,632
Total liabilities and equity	$	3,844,517		$	3,737,372		$	3,467,283		$	3,398,352		$	3,380,022

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Consolidated Statements of Operations

(in thousands, except per share data)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Revenues
Rental revenue	$	100,584		$	93,345		$	91,173		$	91,010		$	89,346		$	376,112		$	352,813
Tenant recoveries and other real estate operations revenue	23,181			21,205			18,084			21,218			19,391			83,688			71,171
Construction contract and other service revenues	27,637			13,608			26,065			37,365			69,553			104,675			343,087
Total revenues	151,402			128,158			135,322			149,593			178,290			564,475			767,071
Expenses
Property operating expenses	47,019			44,260			40,005			48,135			42,567			179,419			157,154
Depreciation and amortization associated with real estate operations	35,347			30,745			29,548			27,596			27,261			123,236			108,529
Construction contract and other service expenses	27,154			13,347			25,402			36,399			68,230			102,302			336,519
General and administrative expenses	6,103			6,079			5,926			5,900			5,965			24,008			23,240
Business development expenses	691			2,886			465			155			2,149			4,197			3,699
Total operating expenses	116,314			97,317			101,346			118,185			146,172			433,162			629,141
Operating income	35,088			30,841			33,976			31,408			32,118			131,313			137,930
Interest expense	(26,878		)	(26,537		)	(25,812		)	(22,638		)	(23,273		)	(101,865		)	(82,187		)
Interest and other income	7,626			395			245			1,302			215			9,568			5,164
Income from continuing operations before equity in income (loss) of unconsolidated entities and income taxes	15,836			4,699			8,409			10,072			9,060			39,016			60,907
Equity in income (loss) of unconsolidated entities	1,005			648			(72		)	(205		)	134			1,376			(941		)
Income tax expense	(33		)	(27		)	(7		)	(41		)	(27		)	(108		)	(196		)
Income from continuing operations	16,808			5,320			8,330			9,826			9,167			40,284			59,770
Discontinued operations	(56		)	1,129			486			832			379			2,391			1,529
Income before gain on sales of real estate	16,752			6,449			8,816			10,658			9,546			42,675			61,299
Gain on sales of real estate, net of income taxes	—			2,477			335			17			—			2,829			—
Net income	16,752			8,926			9,151			10,675			9,546			45,504			61,299
Less net income attributable to noncontrolling interests
Common units in the Operating Partnership	(862		)	(363		)	(364		)	(527		)	(463		)	(2,116		)	(4,495		)
Preferred units in the Operating Partnership	(165		)	(165		)	(165		)	(165		)	(165		)	(660		)	(660		)
Other consolidated entities	(201		)	434			(156		)	(45		)	170			32			185
Net income attributable to COPT	15,524			8,832			8,466			9,938			9,088			42,760			56,329
Preferred share dividends	(4,026		)	(4,025		)	(4,026		)	(4,025		)	(4,026		)	(16,102		)	(16,102		)
Net income attributable to COPT common shareholders	$	11,498		$	4,807		$	4,440		$	5,913		$	5,062		$	26,658		$	40,227
For diluted EPS computations:
Numerator for diluted EPS
Net income attributable to common shareholders	$	11,498		$	4,807		$	4,440		$	5,913		$	5,062		$	26,658		$	40,227
Amount allocable to restricted shares	(264		)	(267		)	(250		)	(290		)	(247		)	(1,071		)	(1,010		)
Numerator for diluted EPS	$	11,234		$	4,540		$	4,190		$	5,623		$	4,815		$	25,587		$	39,217
Denominator:
Weighted average common shares - basic	63,404			58,656			58,489			57,844			57,604			59,611			55,930
Dilutive effect of share-based compensation awards	236			296			421			364			413			333			477
Weighted average common shares - diluted	63,640			58,952			58,910			58,208			58,017			59,944			56,407
Diluted EPS	$	0.18		$	0.08		$	0.07		$	0.10		$	0.08		$	0.43		$	0.70

7

Consolidated Reconciliations of FFO, AFFO, EPS

(in thousands, except per share data)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Net income	$	16,752		$	8,926		$	9,151		$	10,675		$	9,546		$	45,504		$	61,299
Real estate-related depreciation and amortization	35,347			30,745			29,548			27,603			27,475			123,243			109,386
Depreciation and amortization on unconsolidated real estate entities	119			166			171			175			159			631			640
Gain on sales of previously depreciated operating properties, net of income taxes	4			(784		)	—			(297		)	—			(1,077		)	—
FFO	52,222			39,053			38,870			38,156			37,180			168,301			171,325
Noncontrolling interests - preferred units in the Operating Partnership	(165		)	(165		)	(165		)	(165		)	(165		)	(660		)	(660		)
Noncontrolling interests - other consolidated entities	(201		)	434			(156		)	(45		)	170			32			185
Preferred share dividends	(4,026		)	(4,025		)	(4,026		)	(4,025		)	(4,026		)	(16,102		)	(16,102		)
Depreciation and amortization allocable to noncontrolling interests in other consolidated entities	(157		)	(666		)	(297		)	(282		)	(242		)	(1,402		)	(493		)
Basic and diluted FFO allocable to restricted shares	(446		)	(353		)	(346		)	(379		)	(331		)	(1,524		)	(1,629		)
Basic and diluted FFO available to common share and common unit holders	47,227			34,278			33,880			33,260			32,586			148,645			152,626
Straight line rent adjustments	(2,047		)	1,267			(1,473		)	(2,346		)	1,676			(4,599		)	(3,847		)
Amortization of acquisition intangibles included in NOI	(231		)	(96		)	(94		)	(270		)	(679		)	(691		)	(2,126		)
Recurring capital expenditures	(15,960		)	(10,156		)	(7,080		)	(6,211		)	(13,900		)	(39,407		)	(31,738		)
Amortization of discount on Exchangeable Senior Notes, net of amounts capitalized	1,503			1,541			1,488			782			772			5,314			2,955
Operating property acquisition costs	470			2,664			271			19			1,967			3,424			1,967
Diluted AFFO available to common share and common unit holders	$	30,962		$	29,498		$	26,992		$	25,234		$	22,422		$	112,686		$	119,837
Preferred dividends	$	4,026		$	4,025		$	4,026		$	4,025		$	4,026		$	16,102		$	16,102
Preferred distributions	165			165			165			165			165			660			660
Common distributions	1,816			1,834			1,749			1,867			1,988			7,266			7,962
Common dividends	27,597			24,494			23,259			23,160			22,884			98,510			87,596
Total dividends/distributions	$	33,604		$	30,518		$	29,199		$	29,217		$	29,063		$	122,538		$	112,320
Denominator for diluted EPS	63,640			58,952			58,910			58,208			58,017			59,944			56,407
Weighted average common units	4,412			4,453			4,558			5,017			5,078			4,608			5,717
Denominator for diluted FFO per share	68,052			63,405			63,468			63,225			63,095			64,552			62,124
FFO	$	52,222		$	39,053		$	38,870		$	38,156		$	37,180		168,301			171,325
Operating property acquisition costs	470			2,664			271			19			1,967			3,424			1,967
FFO, excluding operating property acquisition costs	$	52,692		$	41,717		$	39,141		$	38,175		$	39,147		171,725			173,292
Diluted FFO available to common share and common unit holders	$	47,227		$	34,278		$	33,880		$	33,260		$	32,586		$	148,645		$	152,626
Operating property acquisition costs	470			2,664			271			19			1,967			3,424			1,967
Diluted FFO available to common share and common unit holders, excluding operating property acquisition costs	$	47,697		$	36,942		$	34,151		$	33,279		$	34,553		$	152,069		$	154,593
Diluted FFO per share, excluding operating property acquisition costs	$	0.70		$	0.58		$	0.54		$	0.53		$	0.55		$	2.36		$	2.49

8

Consolidated Reconciliations of EBITDA, NOI, Discontinued Operations,

Gains on Sales of Real Estate and Certain Non-GAAP Measures

(in thousands)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Net income	$	16,752		$	8,926		$	9,151		$	10,675		$	9,546		$	45,504		$	61,299
Interest expense on continuing and discontinued operations	26,878			26,626			25,921			22,703			23,332			102,128			82,420
Total income tax expense (1)	33			27			7			52			27			119			196
Depreciation of furniture, fixtures and equipment (FF&E)	642			652			632			650			676			2,576			2,425
Real estate-related depreciation and amortization	35,347			30,745			29,548			27,603			27,475			123,243			109,386
EBITDA	$	79,652		$	66,976		$	65,259		$	61,683		$	61,056		$	273,570		$	255,726
Add back:
General and administrative	6,103			6,079			5,926			5,900			5,965			24,008			23,240
Business development	691			2,886			465			155			2,149			4,197			3,699
Depreciation of FF&E	(642		)	(652		)	(632		)	(650		)	(676		)	(2,576		)	(2,425		)
Income from construction contracts and other service operations	(483		)	(261		)	(663		)	(966		)	(1,323		)	(2,373		)	(6,568		)
Interest and other income	(7,626		)	(395		)	(245		)	(1,302		)	(215		)	(9,568		)	(5,164		)
Gain on sales of operating properties	4			(784		)	—			(297		)	—			(1,077		)	—
Non-operational property sales	—			(2,477		)	(335		)	(28		)	—			(2,840		)	—
Equity in (income) loss of unconsolidated entities	(1,005		)	(648		)	72			205			(134		)	(1,376		)	941
NOI	$	76,694		$	70,724		$	69,847		$	64,700		$	66,822		$	281,965		$	269,449
Discontinued Operations
Revenues from real estate operations	$	(52	)	$	478		$	734		$	768		$	713		$	1,928		$	2,871
Property operating expenses	—			(44		)	(139		)	(161		)	(61		)	(344		)	(252		)
Depreciation and amortization	—			—			—			(7		)	(214		)	(7		)	(857		)
Interest	—			(89		)	(109		)	(65		)	(59		)	(263		)	(233		)
Gain on sales of depreciated real estate properties	(4		)	784			—			297			—			1,077			—
Discontinued operations	$	(56	)	$	1,129		$	486		$	832		$	379		$	2,391		$	1,529
Gain on sales of real estate, net, per statements of operations	$	—		$	2,477		$	335		$	17		$	—		$	2,829		$	—
Add income taxes	—			—			—			11			—			11			—
Gain on sales of real estate from discontinued operations	(4		)	784			—			297			—			1,077			—
Gain on sales of real estate from continuing and discontinued operations	(4		)	3,261			335			325			—			3,917			—
Gain on sales of non-operating properties	—			(2,477		)	(335		)	(28		)	—			(2,840		)	—
Gain on sales of operating properties	$	(4	)	$	784		$	—		$	297		$	—		$	1,077		$	—

(1) Includes income taxes from continuing operations, discontinued operations and gains on other sales of real estate (see components on page 10).

9

Reconciliations of Non-GAAP Measurements

(Dollars in thousands)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Total Assets or Denominator for Debt to Total Assets	$	3,844,517		$	3,737,372		$	3,467,283		$	3,398,352		$	3,380,022
Accumulated depreciation	503,032			479,218			464,408			443,246			422,612
Intangible assets on real estate acquisitions, net	113,735			123,307			96,151			94,925			100,671
Assets other than assets included in properties, net	(399,062		)	(388,222		)	(336,769		)	(333,390		)	(350,122		)
Denominator for Debt to Undepreciated Book Value of Real Estate Assets	$	4,062,222		$	3,951,675		$	3,691,073		$	3,603,133		$	3,553,183
GAAP revenues from real estate operations from continuing operations	$	123,765		$	114,550		$	109,257		$	112,228		$	108,737		$	459,800		$	423,984
Revenues from discontinued operations	(52		)	478			734			768			713			1,928			2,871
Real estate revenues from continuing and discontinued operations	$	123,713		$	115,028		$	109,991		$	112,996		$	109,450		$	461,728		$	426,855
GAAP revenues from real estate operations from continuing operations	$	123,765		$	114,550		$	109,257		$	112,228		$	108,737		$	459,800		$	423,984
Property operating expenses	(47,019		)	(44,260		)	(40,005		)	(48,135		)	(42,567		)	(179,419		)	(157,154		)
Revenues from discontinued operations	(52		)	478			734			768			713			1,928			2,871
Property operating expenses from discontinued operations	—			(44		)	(139		)	(161		)	(61		)	(344		)	(252		)
NOI	$	76,694		$	70,724		$	69,847		$	64,700		$	66,822		$	281,965		$	269,449
Depreciation and amortization assoc. with real estate operations from continuing operations	$	35,347		$	30,745		$	29,548		$	27,596		$	27,261		$	123,236		$	108,529
Depreciation and amortization from discontinued operations	—			—			—			7			214			7			857
Real estate-related depreciation and amortization	$	35,347		$	30,745		$	29,548		$	27,603		$	27,475		$	123,243		$	109,386
Total tenant improvements and incentives on operating properties	$	8,761		$	7,789		$	4,630		$	4,071		$	2,359		$	25,251		$	13,931
Total capital improvements on operating properties	6,879			1,717			1,524			870			9,475			10,990			16,270
Total leasing costs for operating properties	4,573			2,004			1,350			1,338			2,801			9,265			7,232
Less: Nonrecurring tenant improvements and incentives on operating properties	(3,003		)	(1,067		)	(136		)	(77		)	(851		)	(4,283		)	(3,631		)
Less: Nonrecurring capital improvements on operating properties	(1,342		)	(171		)	(293		)	(60		)	(117		)	(1,866		)	(1,457		)
Less: Nonrecurring leasing costs for operating properties	10			(120		)	(3		)	54			(186		)	(59		)	(1,102		)
Add: Recurring capital expenditures on operating properties held through joint ventures	82			4			8			15			419			109			495
Recurring capital expenditures	$	15,960		$	10,156		$	7,080		$	6,211		$	13,900		$	39,407		$	31,738
Interest expense from continuing operations	$	26,878		$	26,537		$	25,812		$	22,638		$	23,273		$	101,865		$	82,187
Interest expense from discontinued operations	—			89			109			65			59			263			233
Total interest expense	$	26,878		$	26,626		$	25,921		$	22,703		$	23,332		$	102,128		$	82,420
Less: Amortization of deferred financing costs	(1,696		)	(1,554		)	(1,495		)	(1,126		)	(1,125		)	(5,871		)	(4,214		)
Less: Amortization of discount on Exchangeable Senior Notes, net of amounts capitalized	(1,503		)	(1,541		)	(1,488		)	(782		)	(772		)	(5,314		)	(2,955		)
Denominator for interest coverage	$	23,679		$	23,531		$	22,938		$	20,795		$	21,435		$	90,943		$	75,251
Scheduled principal amortization	3,607			3,420			3,500			3,469			3,289			13,996			11,489
Denominator for debt service coverage	$	27,286		$	26,951		$	26,438		$	24,264		$	24,724		$	104,939		$	86,740
Scheduled principal amortization	(3,607		)	(3,420		)	(3,500		)	(3,469		)	(3,289		)	(13,996		)	(11,489		)
Preferred dividends - redeemable non-convertible	4,026			4,025			4,026			4,025			4,026			16,102			16,102
Preferred distributions	165			165			165			165			165			660			660
Denominator for fixed charge coverage	$	27,870		$	27,721		$	27,129		$	24,985		$	25,626		$	107,705		$	92,013
Common share dividends	$	27,597		$	24,494		$	23,259		$	23,160		$	22,884		$	98,510		$	87,596
Common unit distributions	1,816			1,834			1,749			1,867			1,988			7,266			7,962
Dividends and distributions for FFO and AFFO payout ratios	$	29,413		$	26,328		$	25,008		$	25,027		$	24,872		$	105,776		$	95,558
Debt, net	$	2,323,681		$	2,468,419		$	2,182,375		$	2,107,131		$	2,053,841		$	2,323,681		$	2,053,841
Less: Construction in progress	(386,195		)	(344,924		)	(319,846		)	(317,283		)	(270,376		)	(386,195		)	(270,376		)
Adjusted debt for adjusted debt to EBITDA ratio	$	1,937,486		$	2,123,495		$	1,862,529		$	1,789,848		$	1,783,465		$	1,937,486		$	1,783,465
Income tax expense from continuing operations	$	33		$	27		$	7		$	41		$	27		$	108		$	196
Income tax expense from gain on other sales of real estate	—			—			—			11			—			11			—
Total income tax expense	$	33		$	27		$	7		$	52		$	27		$	119		$	196

10

Real Estate Revenues from Continuing and Discontinued Operations by Geographic Region

(Dollars in thousands)

	Three Months Ended										Year Ended
	12/31/10		9/30/10		6/30/10		3/31/10		12/31/09		12/31/10		12/31/09
Office Properties:
Baltimore/Washington Corridor	$	52,829	$	51,946	$	50,623	$	52,058	$	50,681	$	207,456	$	197,610
Northern Virginia	19,283		18,949		18,172		18,659		19,186		75,063		79,132
Greater Baltimore	18,870		18,288		16,827		17,865		16,265		71,850		58,275
Colorado Springs	6,235		6,176		6,154		6,332		6,190		24,897		23,125
Suburban Maryland	5,235		5,243		5,452		5,829		4,697		21,759		19,620
St. Mary’s and King George Counties	3,417		3,431		3,530		3,589		3,566		13,967		13,960
San Antonio	7,898		5,609		4,228		3,938		3,805		21,673		13,566
Washington, DC - Capitol Riverfront	4,543		135		—		—		—		4,678		—
Greater Philadelphia	1,794		1,793		1,510		1,202		1,627		6,299		7,983
Other	3,609		3,458		3,495		3,524		3,433		14,086		13,584
Real estate revenues from cont. and discont. operations	$	123,713	$	115,028	$	109,991	$	112,996	$	109,450	$	461,728	$	426,855

NOI by Geographic Region

(Dollars in thousands)

	Three Months Ended										Year Ended
	12/31/10		9/30/10		6/30/10		3/31/10		12/31/09		12/31/10		12/31/09
Office Properties:
Baltimore/Washington Corridor	$	33,442	$	33,001	$	33,770	$	29,903	$	31,647	$	130,116	$	124,708
Northern Virginia	12,382		11,754		11,466		11,346		11,684		46,948		49,021
Greater Baltimore	11,528		10,460		9,516		8,855		9,201		40,359		32,715
Colorado Springs	4,026		3,796		3,915		4,023		3,662		15,760		15,734
Suburban Maryland	3,096		2,625		3,253		3,128		2,458		12,102		11,227
St. Mary’s and King George Counties	2,377		2,279		2,489		2,482		2,641		9,627		10,469
San Antonio	3,877		2,912		2,128		2,309		2,354		11,226		9,087
Washington, DC - Capitol Riverfront	2,835		135		—		—		—		2,970		—
Greater Philadelphia	1,315		1,561		710		439		981		4,025		6,712
Other	1,816		2,201		2,600		2,215		2,194		8,832		9,776
NOI	$	76,694	$	70,724	$	69,847	$	64,700	$	66,822	$	281,965	$	269,449

11

Same Office Property Cash NOI

(Dollars in thousands)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Office Properties: (1)
Baltimore/Washington Corridor	$	30,059		$	33,046		$	31,326		$	27,172		$	31,709		$	121,603		$	122,136
Northern Virginia	11,696			10,543			11,781			11,603			11,637			45,623			49,242
Greater Baltimore	8,410			7,818			7,608			6,612			6,808			30,448			28,812
Colorado Springs	3,483			3,418			3,423			3,423			2,995			13,747			13,354
Suburban Maryland	1,907			1,601			1,947			2,200			2,194			7,655			10,247
St. Mary’s and King George Counties	2,413			2,325			2,538			2,496			2,630			9,772			10,239
San Antonio	1,973			1,962			1,735			1,906			2,019			7,576			7,518
Greater Philadelphia	723			773			677			406			783			2,579			2,687
Other	1,976			2,025			1,908			1,910			1,884			7,819			7,573
Total Office Properties	$	62,640		$	63,511		$	62,943		$	57,728		$	62,659		$	246,822		$	251,808
Less: Lease termination fees, gross	(2,059		)	(209		)	(1,086		)	(278		)	(347		)	(3,632		)	(5,531		)
Same office property cash NOI, excluding gross lease termination fees	$	60,581		$	63,302		$	61,857		$	57,450		$	62,312		$	243,190		$	246,277

Same Office Property GAAP NOI

(Dollars in thousands)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Office Properties: (1)
Baltimore/Washington Corridor	$	30,182		$	29,831		$	31,789		$	28,179		$	29,895		$	119,981		$	120,646
Northern Virginia	11,564			10,711			11,487			11,476			11,829			45,238			49,449
Greater Baltimore	8,836			7,896			7,889			6,861			7,385			31,482			30,897
Colorado Springs	3,645			3,569			3,581			3,609			3,223			14,404			14,361
Suburban Maryland	1,946			1,668			2,141			2,224			2,327			7,979			10,789
St. Mary’s and King George Counties	2,378			2,280			2,491			2,483			2,652			9,632			10,485
San Antonio	2,302			2,338			2,115			2,287			2,405			9,042			9,211
Greater Philadelphia	713			762			680			513			796			2,668			2,590
Other	2,168			2,227			2,136			2,147			2,130			8,678			8,668
Total Office Properties	$	63,734		$	61,282		$	64,309		$	59,779		$	62,642		$	249,104		$	257,096
GAAP net operating income for same office properties	$	63,734		$	61,282		$	64,309		$	59,779		$	62,642		$	249,104		$	257,096
Add (less): Straight-line rent adjustments	(433		)	2,651			(875		)	(1,480		)	640			(137		)	(3,305		)
Less: Amortization of deferred market rental revenue	(661		)	(422		)	(491		)	(571		)	(623		)	(2,145		)	(1,983		)
Same office property cash NOI	$	62,640		$	63,511		$	62,943		$	57,728		$	62,659		$	246,822		$	251,808
Less: Lease termination fees, gross	(2,059		)	(209		)	(1,086		)	(278		)	(347		)	(3,632		)	(5,531		)
Same office property cash NOI, excluding gross lease termination fees	$	60,581		$	63,302		$	61,857		$	57,450		$	62,312		$	243,190		$	246,277

(1) Same office properties represent buildings owned and 100% operational since January 1, 2009.

12

Operating Ratios

(Dollars in thousands except per share data and ratios)

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
OPERATING RATIOS — All computations include the effect of discontinued operations
Net income as a % of Real estate revenues from cont. and discont. operations (Net income / Real estate revenues from cont. and discont. operations)	13.5		%	7.8		%	8.3		%	9.4		%	8.7		%	9.9		%	14.4		%
NOI as a % of Real estate revenues from cont. and discont. operations (NOI / Real estate revenues from cont. and discont. operations)	62.0		%	61.5		%	63.5		%	57.3		%	61.1		%	61.1		%	63.1		%
EBITDA as a % of Real estate revenues from cont. and discont. operations (EBITDA / Real estate revenues from cont. and discont. operations)	64.4		%	58.2		%	59.3		%	54.6		%	55.8		%	59.2		%	59.9		%
G&A as a % of Real estate revenues from cont. and discont. operations (G&A / Real estate revenues from cont. and discont. operations)	4.9		%	5.3		%	5.4		%	5.2		%	5.4		%	5.2		%	5.4		%
G&A as a % of EBITDA (G&A / EBITDA)	7.7		%	9.1		%	9.1		%	9.6		%	9.8		%	8.8		%	9.1		%
Recurring Capital Expenditures	$	15,960		$	10,156		$	7,080		$	6,211		$	13,900		$	39,407		$	31,738
Recurring Capital Expenditures per average square foot of consolidated properties	$	0.78		$	0.50		$	0.36		$	0.32		$	0.73		$	1.98		$	1.68
Recurring Capital Expenditures as a % of NOI	20.8		%	14.4		%	10.1		%	9.6		%	20.8		%	14.0		%	11.8		%

13

Debt Analysis

(Dollars in thousands)

	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09
Debt Outstanding
Mortgage Loans	$	1,485,860		$	1,449,817		$	1,432,544		$	1,452,845		$	1,439,608
Construction Loans (1)	159,092			138,655			119,640			100,225			93,086
Unsecured Revolving Credit Facility (2)	295,000			498,000			250,000			397,000			365,000
Exchangeable Senior Notes	383,729			381,947			380,191			157,061			156,147
	$	2,323,681		$	2,468,419		$	2,182,375		$	2,107,131		$	2,053,841
Interest Rate Data
Fixed-Mortgage Loans	$	1,175,305		$	1,179,060		$	1,161,652		$	1,165,073		$	1,168,462
Fixed-Exchangeable Senior Notes	383,729			381,947			380,191			157,061			156,147
Variable	504,712			687,412			420,532			564,997			509,232
Variable Subject to Interest Rate Swaps (3)	259,935			220,000			220,000			220,000			220,000
	$	2,323,681		$	2,468,419		$	2,182,375		$	2,107,131		$	2,053,841
% of Fixed Rate Loans (3)	78.28		%	72.15		%	80.73		%	73.19		%	75.21		%
% of Variable Rate Loans (3)	21.72		%	27.85		%	19.27		%	26.81		%	24.79		%
	100.00		%	100.00		%	100.00		%	100.00		%	100.00		%
	Three Months Ended															Year Ended
	12/31/2010			9/30/2010			6/30/2010			3/31/2010			12/31/2009			12/31/2010		12/31/2009
Average Contract Interest Rates
Mortgage & Construction Loans	5.30		%	5.39		%	5.43		%	5.45		%	5.49		%	5.40	%	5.25	%
Unsecured Revolving Credit Facility (4)	2.07		%	2.19		%	2.53		%	1.93		%	2.43		%	2.14	%	2.75	%
Exchangeable Senior Notes (5)	3.95		%	3.95		%	3.95		%	3.50		%	3.50		%	3.88	%	3.50	%
Total Weighted Average	4.92		%	5.06		%	5.26		%	4.83		%	5.07		%	5.01	%	4.86	%
Debt ratios (coverage ratios excluding capitalized interest) — All coverage computations include the effect of discontinued operations
NOI interest coverage ratio	3.24x			3.01x			3.05x			3.11x			3.12x			3.10x		3.58x
EBITDA interest coverage ratio	3.36x			2.85x			2.85x			2.97x			2.85x			3.01x		3.40x
NOI debt service coverage ratio	2.81x			2.62x			2.64x			2.67x			2.70x			2.69x		3.11x
EBITDA debt service coverage ratio	2.92x			2.49x			2.47x			2.54x			2.47x			2.61x		2.95x
NOI fixed charge coverage ratio	2.75x			2.55x			2.57x			2.59x			2.61x			2.62x		2.93x
EBITDA fixed charge coverage ratio	2.86x			2.42x			2.41x			2.47x			2.38x			2.54x		2.78x
Debt to EBITDA ratio (6)	7.29x			9.21x			8.36x			8.54x			8.41x
Adjusted debt to EBITDA ratio (7)	6.08x			7.93x			7.14x			7.25x			7.30x

(1)Includes $142.3 million due under our Revolving Construction Facility at December 31, 2010.  This facility provides for the borrowing of up to $225.0 million to finance construction of the Company’s wholly owned buildings.

(2)As of December 31, 2010, our borrowing capacity under the Revolving Credit Facility was $800.0 million, of which $503.1 million was available.

(3)Includes the effect of interest rate swaps in effect during certain of the periods set forth above that hedge the risk of changes in interest rates on certain of our one-month LIBOR-based variable rate debt.

(4)Includes effect of interest expense incurred on interest rate swaps.

(5)Represents the weighted average of the stated interest rates on our Exchangeable Senior Notes.

(6)  Represents debt divided by EBITDA for the three month period multiplied by four.

(7)Represents debt adjusted to subtract construction in progress as of period end divided by EBITDA for the three month period multiplied by four.

14

Debt Maturity Schedule -  December 31, 2010

(Dollars in thousands)

			Non-Recourse Debt (1)						Recourse Debt (1)
Year of Maturity			Annual Amortization of Monthly Payments		Balloon Payments Due on Maturity		Weighted Average Interest Rate of Amounts Maturing		Annual Amortization of Monthly Payments		Balloon Payments Due on Maturity		Weighted Average Interest Rate of Amounts Maturing			Revolver (2)			Total Scheduled Payments
January - March			$	3,604	$	—	N/A		$	244	$	—	N/A			$	—		$	3,848
April - June			3,609		—		N/A		246		159,092		1.98		%	—			162,947
July - September			3,479		102,264		5.47	%	257		—		N/A			295,000			401,000
October - December			3,186		—		N/A		258		—		N/A			—			3,444
Total 2011			$	13,878	$	102,264	5.47	%	$	1,005	$	159,092	1.98		%	$	295,000		$	571,239
2011	(3	)	$	13,878	$	102,264			$	1,005	$	159,092				$	295,000		$	571,239
2012			12,802		257,523				1,065		—					—			271,390
2013			10,075		134,843				1,131		—					—			146,049
2014	(4	)	6,688		175,931				840		26,766					—			210,225
2015			5,209		135,734				530		15,000					—			156,473
2016			3,481		274,605				556		—					—			278,642
2017			193		300,610				585		—					—			301,388
2018			—		—				617		—					—			617
2019			—		—				573		39					—			612
2020			—		—				200		—					—			200
2021			—		—				200		—					—			200
2022			—		—				200		—					—			200
2023			—		—				200		—					—			200
2024			—		—				200		—					—			200
2025			—		—				200		—					—			200
2026			—		—				50		11					—			61
			$	52,326	$	1,381,510			$	8,152	$	200,908				$	295,000		$	1,937,896
					Net premium														2,056
					Mortgage and Other Loans Payable														$	1,939,952
													3.5		%	4.25		%
					Exchangeable Senior Notes-Face Amount								$	162,500		$	240,000		$	402,500
					Net discount								(2,617		)	(16,154		)	(18,771		)
					Exchangeable Senior Notes (5)								$	159,883		$	223,846		383,729
					Total Debt														$	2,323,681

Notes:

(1) Certain mortgages contain extension options, generally either for a period of six months or one year, subject to certain conditions. The maturity dates presented above in the table assume that the extension options have not been exercised.

(2) As of December 31, 2010, our borrowing capacity under the Revolving Credit Facility was $800.0 million, of which $503.1 million was available.

(3) Includes $295.0 million due under our Revolving Credit Facility at December 31, 2010 that may be extended by us for a one-year period, subject to certain conditions.  Also includes $142.3 million due under our Revolving Construction Facility at December 31, 2010 that was extended to May 2012 in January 2011; this facility provides for the borrowing of up to $225.0 million to finance construction of the Company’s wholly owned buildings.

(4) We have $74.3 million of nonrecourse debt maturing in 2034 that may be prepaid in 2014, subject to certain conditions. The above table includes $69.2 million in maturities on these loans in 2014.

(5) 3.5% Exchangeable Senior Notes mature in September 2026 but are subject to a put by the holders in September 2011 and every five years thereafter.  4.25% Exchangeable Senior Notes mature in April 2030 but are subject to a put by the holders in April 2015 and every five years thereafter.

15

Quarterly Equity Analysis

(Dollars and shares in thousands except per share data)

	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09
Common Equity - End of Quarter
Common Shares	66,932			59,406			59,288			58,927			58,343
Common Units	4,403			4,446			4,456			4,757			5,066
Total	71,334			63,852			63,744			63,684			63,409
End of Quarter Common Share Price	$	34.95		$	37.31		$	37.76		$	40.13		$	36.63
Market Value of Common Shares/Units	$	2,493,134		$	2,382,318		$	2,406,973		$	2,555,639		$	2,322,672
Common Shares Trading Volume
Average Daily Volume (Shares)	784			728			887			654			751
Average Daily Volume	$	27,910		$	27,241		$	35,095		$	24,583		$	26,570
As a Percentage of Weighted Average Common Shares	1.2		%	1.2		%	1.5		%	1.1		%	1.3		%
Common Share Price Range (price per share)
Quarterly High	$	38.96		$	39.85		$	43.61		$	42.44		$	38.29
Quarterly Low	$	33.33		$	35.04		$	34.82		$	32.69		$	31.77
Quarterly Average	$	35.59		$	37.44		$	39.58		$	37.57		$	35.38
Convertible Preferred Equity - End of Quarter
Convertible Series I Preferred Units Outstanding	352			352			352			352			352
Conversion Ratio	0.5000			0.5000			0.5000			0.5000			0.5000
Common Shares Issued Assuming Conversion	176			176			176			176			176
Convertible Series K Preferred Shares Outstanding	532			532			532			532			532
Conversion Ratio	0.8163			0.8163			0.8163			0.8163			0.8163
Common Shares Issued Assuming Conversion	434			434			434			434			434
Nonconvertible Preferred Equity - End of Quarter
Redeemable Series G Shares Outstanding	2,200			2,200			2,200			2,200			2,200
Redeemable Series H Shares Outstanding	2,000			2,000			2,000			2,000			2,000
Redeemable Series J Shares Outstanding	3,390			3,390			3,390			3,390			3,390
Total Nonconvertible Preferred Equity	7,590			7,590			7,590			7,590			7,590
Convertible Preferred Equity
Convertible Series K Shares Outstanding	884			884			884			884			884
Total Preferred Equity	8,474			8,474			8,474			8,474			8,474
Nonconvertible Preferred Equity ($25 par value)
Redeemable Series G Shares	$	55,000		$	55,000		$	55,000		$	55,000		$	55,000
Redeemable Series H Shares	50,000			50,000			50,000			50,000			50,000
Redeemable Series J Shares	84,750			84,750			84,750			84,750			84,750
Total Nonconvertible Preferred Equity	$	189,750		$	189,750		$	189,750		$	189,750		$	189,750
Convertible Preferred Equity ($25 liquidation value)
Convertible Series I Units	$	8,800		$	8,800		$	8,800		$	8,800		$	8,800
Convertible Preferred Equity ($50 liquidation value)
Convertible Series K Shares	26,583			26,583			26,583			26,583			26,583
Total Convertible Preferred Equity	$	35,383		$	35,383		$	35,383		$	35,383		$	35,383
Total Liquidation Value of Preferred Equity	$	225,133		$	225,133		$	225,133		$	225,133		$	225,133
Weighted Average Shares for quarter ended:
Common Shares Outstanding	63,404			58,656			58,489			57,844			57,604
Dilutive effect of share-based compensation awards	236			296			421			364			413
Common Units	4,412			4,453			4,558			5,017			5,078
Denominator for FFO per share - diluted	68,052			63,405			63,468			63,225			63,095
Capitalization
Liquidation Value of Preferred Shares/Units	$	225,133		$	225,133		$	225,133		$	225,133		$	225,133
Market Value of Common Shares/Units	2,493,134			2,382,318			2,406,973			2,555,639			2,322,672
Total Equity Market Capitalization	$	2,718,267		$	2,607,451		$	2,632,107		$	2,780,772		$	2,547,805
Total Debt	$	2,323,681		$	2,468,419		$	2,182,375		$	2,107,131		$	2,053,841
Total Market Capitalization	$	5,041,948		$	5,075,870		$	4,814,482		$	4,887,903		$	4,601,646
Debt to Total Market Capitalization	46.1		%	48.6		%	45.3		%	43.1		%	44.6		%
Debt to Total Assets	60.4		%	66.0		%	62.9		%	62.0		%	60.8		%
Debt to Undepreciated Book Value of Real Estate Assets	57.2		%	62.5		%	59.1		%	58.5		%	57.8		%

16

Dividend Analysis

	Three Months Ended															Year Ended
	12/31/10			9/30/10			6/30/10			3/31/10			12/31/09			12/31/10			12/31/09
Common Share Dividends
Dividends per share/unit	$	0.4125		$	0.4125		$	0.3925		$	0.3925		$	0.3925		$	1.6100		$	1.5300
Increase over prior period	0.0		%	5.1		%	0.0		%	0.0		%	0.0		%	5.2		%	7.4		%
Common Dividend Payout Ratios
Diluted FFO Payout, excluding operating property acquisition costs	61.7		%	71.3		%	73.2		%	75.2		%	72.0		%	69.6		%	61.8		%
Diluted AFFO Payout	95.0		%	89.3		%	92.6		%	99.2		%	110.9		%	93.9		%	79.7		%
Dividend Coverage - Diluted FFO, excluding operating property acquisition costs	1.62x			1.40x			1.37x			1.33x			1.39x			1.44x			1.62x
Dividend Coverage - Diluted AFFO	1.05x			1.12x			1.08x			1.01x			0.90x			1.07x			1.25x
Common Dividend Yields
Dividend Yield at Quarter End	4.72		%	4.42		%	4.16		%	3.91		%	4.29		%
Series I Preferred Unit Distributions
Preferred Unit Distributions Per Unit	$	0.46875		$	0.46875		$	0.46875		$	0.46875		$	0.46875
Preferred Unit Distributions Yield	7.500		%	7.500		%	7.500		%	7.500		%	7.500		%
Quarter End Recorded Book Value	$	25.00		$	25.00		$	25.00		$	25.00		$	25.00
Series G Preferred Share Dividends
Preferred Share Dividends Per Share	$	0.50000		$	0.50000		$	0.50000		$	0.50000		$	0.50000
Preferred Share Dividend Yield	8.000		%	8.000		%	8.000		%	8.000		%	8.000		%
Quarter End Recorded Book Value	$	25.00		$	25.00		$	25.00		$	25.00		$	25.00
Series H Preferred Share Dividends
Preferred Share Dividends Per Share	$	0.46875		$	0.46875		$	0.46875		$	0.46875		$	0.46875
Preferred Share Dividend Yield	7.500		%	7.500		%	7.500		%	7.500		%	7.500		%
Quarter End Recorded Book Value	$	25.00		$	25.00		$	25.00		$	25.00		$	25.00
Series J Preferred Share Dividends
Preferred Share Dividends Per Share	$	0.47656		$	0.47656		$	0.47656		$	0.47656		$	0.47656
Preferred Share Dividend Yield	7.625		%	7.625		%	7.625		%	7.625		%	7.625		%
Quarter End Recorded Book Value	$	25.00		$	25.00		$	25.00		$	25.00		$	25.00
Series K Preferred Share Dividends
Preferred Share Dividends Per Share	$	0.70000		$	0.70000		$	0.70000		$	0.70000		$	0.70000
Preferred Share Dividend Yield	5.600		%	5.600		%	5.600		%	5.600		%	5.600		%
Quarter End Recorded Book Value	$	50.00		$	50.00		$	50.00		$	50.00		$	50.00

17

Investor Composition and Analyst Coverage

as of December 31, 2010

			As if Converted		Diluted
	Common	Common	Preferred		Ownership
	Shares	Units	Shares / Units	Total	% of Total
SHAREHOLDER CLASSIFICATION
Insiders	1,037,762	3,740,427	—	4,778,189	6.64	%
Non-insiders	65,893,820	662,300	610,014	67,166,134	93.36	%
	66,931,582	4,402,727	610,014	71,944,323	100.00	%

	12/31/10	9/30/10	6/30/10	3/31/10	12/31/09
RESEARCH COVERAGE
BMO Capital Markets	x	x	x	x	x
Citigroup Global Markets	x	x	x	x	x
Cowen and Company	x	n/a	n/a	n/a	n/a
Friedman Billings Ramsey & Co.	x	x	n/a	n/a	x
Green Street Advisors	x	x	x	x	x
ISI Group	x	x	x	x	x
Jeffries & Co.	x	x	n/a	n/a	n/a
JP Morgan	x	x	x	x	x
Keefe, Bruyette & Woods	x	x	n/a	n/a	n/a
KeyBanc Capital Markets	x	x	x	x	n/a
Macquarie Securities	x	x	x	x	n/a
Raymond James	x	x	x	x	x
RBC Capital Markets	x	x	x	x	x
Robert W. Baird & Co. Incorporated	x	x	x	x	x
Stifel, Nicolaus & Company, Incorporated	x	x	x	x	x
Wells Fargo Securities	x	x	x	x	x

18

Office Property Summary by Region - December 31, 2010

Wholly Owned Properties

Operating Property Count		Submarket	Business Park	Year Built or Renovated	S or M	Total Operational Square Feet	Total Square Feet Under Construction / Redevelopment
	Baltimore /Washington Corridor
1	2730 Hercules Road	BWI Airport	NBP	1990	M	240,336
2	300 Sentinel Drive (300 NBP)	BWI Airport	NBP	2009	M	192,562
3	304 Sentinel Drive (304 NBP)	BWI Airport	NBP	2005	M	162,647
4	306 Sentinel Drive (306 NBP)	BWI Airport	NBP	2006	M	155,883
5	2720 Technology Drive (220 NBP)	BWI Airport	NBP	2004	M	156,730
6	302 Sentinel Drive (302 NBP)	BWI Airport	NBP	2007	M	153,598
7	2711 Technology Drive (211 NBP)	BWI Airport	NBP	2002	M	152,196
8	308 Sentinel Drive (308 NBP)	BWI Airport	NBP	2010	M	31,128	120,415
9	320 Sentinel Way (320 NBP)	BWI Airport	NBP	2007	M	125,681
10	318 Sentinel Way (318 NBP)	BWI Airport	NBP	2005	M	125,681
11	322 Sentinel Way (322 NBP)	BWI Airport	NBP	2006	M	125,568
12	324 Sentinel Way (324 NBP)	BWI Airport	NBP	2010	M	125,118
13	140 National Business Parkway	BWI Airport	NBP	2003	M	119,904
14	132 National Business Parkway	BWI Airport	NBP	2000	M	118,598
15	2721 Technology Drive (221 NBP)	BWI Airport	NBP	2000	M	118,093
16	2701 Technology Drive (201 NBP)	BWI Airport	NBP	2001	M	117,450
17	2691 Technology Drive (191 NBP)	BWI Airport	NBP	2005	M	103,683
18	134 National Business Parkway	BWI Airport	NBP	1999	M	93,482
19	135 National Business Parkway	BWI Airport	NBP	1998	M	87,422
20	133 National Business Parkway	BWI Airport	NBP	1997	M	87,401
21	141 National Business Parkway	BWI Airport	NBP	1990	M	87,206
22	131 National Business Parkway	BWI Airport	NBP	1990	M	69,336
23	114 National Business Parkway	BWI Airport	NBP	2002	S	9,908
24	314 Sentinel Way (314 NBP)	BWI Airport	NBP	2008	S	4,462
						2,764,073	120,415
1	1550 West Nursery Road	BWI Airport	APS	2009	M	162,101
2	1306 Concourse Drive	BWI Airport	APS	1990	M	116,307
3	1304 Concourse Drive	BWI Airport	APS	2002	M	101,792
4	900 Elkridge Landing Road	BWI Airport	APS	1982	M	100,824
5	880 Elkridge Landing Road	BWI Airport	APS	1981	M	99,524
6	1199 Winterson Road	BWI Airport	APS	1988	M	96,636
7	920 Elkridge Landing Road	BWI Airport	APS	1982	M	96,566
8	1302 Concourse Drive	BWI Airport	APS	1996	M	84,053
9	881 Elkridge Landing Road	BWI Airport	APS	1986	M	73,572
10	1099 Winterson Road	BWI Airport	APS	1988	M	70,583
11	1190 Winterson Road	BWI Airport	APS	1987	M	68,899
12	849 International Drive	BWI Airport	APS	1988	M	68,768
13	911 Elkridge Landing Road	BWI Airport	APS	1985	M	68,296
14	1201 Winterson Road	BWI Airport	APS	1985	M	67,903
15	999 Corporate Boulevard	BWI Airport	APS	2000	M	66,889
16	901 Elkridge Landing Road	BWI Airport	APS	1984	M	58,035
17	891 Elkridge Landing Road	BWI Airport	APS	1984	M	57,955
18	800 International Drive	BWI Airport	APS	1988	S	57,379
19	930 International Drive	BWI Airport	APS	1986	S	57,272
20	900 International Drive	BWI Airport	APS	1986	S	57,140
21	939 Elkridge Landing Road	BWI Airport	APS	1983	M	54,280
22	921 Elkridge Landing Road	BWI Airport	APS	1983	M	54,175
23	938 Elkridge Landing Road	BWI Airport	APS	1984	M	52,988
24	870 Elkridge Landing Road	BWI Airport	APS	1981	S	5,627
						1,797,564
1	7467 Ridge Road	BWI Airport	Comm./Pkwy.	1990	M	74,136
2	7240 Parkway Drive	BWI Airport	Comm./Pkwy.	1985	M	74,153
3	7272 Park Circle Drive	BWI Airport	Comm./Pkwy.	1991/1996	M	59,888
4	7318 Parkway Drive	BWI Airport	Comm./Pkwy.	1984	S	59,204
5	7320 Parkway Drive	BWI Airport	Comm./Pkwy.	1983	S	56,964
6	1340 Ashton Road	BWI Airport	Comm./Pkwy.	1989	S	45,867
7	1362 Mellon Road	BWI Airport	Comm./Pkwy.	2006	M	43,232
8	1334 Ashton Road	BWI Airport	Comm./Pkwy.	1989	S	37,317
9	1331 Ashton Road	BWI Airport	Comm./Pkwy.	1989	S	28,998
10	1350 Dorsey Road	BWI Airport	Comm./Pkwy.	1989	S	18,698
11	1344 Ashton Road	BWI Airport	Comm./Pkwy.	1989	M	16,964
12	1341 Ashton Road	BWI Airport	Comm./Pkwy.	1989	S	15,947
13	1343 Ashton Road	BWI Airport	Comm./Pkwy.	1989	S	9,903
14	1348 Ashton Road	BWI Airport	Comm./Pkwy.	1988	S	3,108
						544,379	—
62	Subtotal (continued on next page)					5,106,016	120,415

The S or M notation indicates single story or multi-story, respectively.

19

Office Property Summary by Region - December 31, 2010 (continued)

Wholly Owned Properties

Operating Property Count		Submarket	Business Park	Year Built or Renovated	S or M	Total Operational Square Feet	Total Square Feet Under Construction / Redevelopment
62	Subtotal (continued from prior page)					5,106,016	120,415
1	5520 Research Park Drive (UMBC) (1)	BWI Airport	bwtech@UMBC	2009	M	103,990
2	5522 Research Park Drive (UMBC) (1)	BWI Airport	bwtech@UMBC	2007	S	23,500
						127,490
1	2500 Riva Road	Annapolis		2000	M	155,000
1	Old Annapolis Road	Howard Co. Perimeter	Oakland Ridge	1985	M	171,436
1	7125 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1973/1999	M	470,249
2	7000 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1999	M	145,806
3	6721 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2009	M	131,451
4	6731 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2002	M	123,847
5	6711 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2006-2007	M	123,599
6	6940 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1999	M	108,822
7	6950 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1998	M	112,861
8	7067 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2001	M	86,027
9	8621 Robert Fulton Drive	Howard Co. Perimeter	Columbia Gateway	2005-2006	M	86,033
10	6750 Alexander Bell Drive	Howard Co. Perimeter	Columbia Gateway	2001	M	75,328
11	6700 Alexander Bell Drive	Howard Co. Perimeter	Columbia Gateway	1988	M	76,347
12	6740 Alexander Bell Drive	Howard Co. Perimeter	Columbia Gateway	1992	M	63,480
13	7015 Albert Einstein Drive	Howard Co. Perimeter	Columbia Gateway	1999	S	61,203
14	8671 Robert Fulton Drive	Howard Co. Perimeter	Columbia Gateway	2002	S	56,350
15	6716 Alexander Bell Drive	Howard Co. Perimeter	Columbia Gateway	1990	M	52,131
16	8661 Robert Fulton Drive	Howard Co. Perimeter	Columbia Gateway	2002	S	49,307
17	7142 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1994	S	47,668
18	7130 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1989	S	46,460
19	6708 Alexander Bell Drive	Howard Co. Perimeter	Columbia Gateway	1988	M	39,203
20	7065 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2000	S	38,560
21	7138 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1990	S	38,225
22	7063 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2000	S	36,472
23	6760 Alexander Bell Drive	Howard Co. Perimeter	Columbia Gateway	1991	M	36,225
24	7150 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1991	S	35,812
25	7061 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2000	M	29,910
26	6724 Alexander Bell Drive	Howard Co. Perimeter	Columbia Gateway	2001	M	28,107
27	7134 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	1990	S	21,991
28	6741 Columbia Gateway Drive	Howard Co. Perimeter	Columbia Gateway	2008	S	4,592
						2,226,066	—
1	7200 Riverwood Drive	Howard Co. Perimeter	Rivers Corporate Park	1986	S	160,000
2	7160 Riverwood Drive	Howard Co. Perimeter	Rivers Corporate Park	2000	M	61,984
3	9140 Guilford Road	Howard Co. Perimeter	Rivers Corporate Park	1983	S	40,286
4	7150 Riverwood Drive	Howard Co. Perimeter	Rivers Corporate Park	2000	M	39,496
5	9160 Guilford Road	Howard Co. Perimeter	Rivers Corporate Park	1984	M	37,034
6	7170 Riverwood Drive	Howard Co. Perimeter	Rivers Corporate Park	2000	M	29,162
7	9150 Guilford Road	Howard Co. Perimeter	Rivers Corporate Park	1984	S	18,592
8	10280 Old Columbia Road	Howard Co. Perimeter	Rivers Corporate Park	1988/2001	S	16,195
9	10270 Old Columbia Road	Howard Co. Perimeter	Rivers Corporate Park	1988/2001	S	15,910
10	9130 Guilford Road	Howard Co. Perimeter	Rivers Corporate Park	1984	S	13,700
11	10290 Old Columbia Road	Howard Co. Perimeter	Rivers Corporate Park	1988/2001	S	10,263
						442,622	—
1	9720 Patuxent Woods Drive	Howard Co. Perimeter	Owen Brown South	1986/2001	M	40,004
2	9740 Patuxent Woods Drive	Howard Co. Perimeter	Owen Brown South	1986/2001	M	38,292
3	9700 Patuxent Woods Drive	Howard Co. Perimeter	Owen Brown South	1986/2001	M	31,220
4	9730 Patuxent Woods Drive	Howard Co. Perimeter	Owen Brown South	1986/2001	M	30,485
5	9710 Patuxent Woods Drive	Howard Co. Perimeter	Owen Brown South	1986/2001	M	14,778
						154,779	—
1	9020 Mendenhall Court	Howard Co. Perimeter	Sieling Business Park	1982/2005	S	49,217
111	Total Baltimore/Washington Corridor					8,432,626	120,415

The S or M notation indicates single story or multi-story building, respectively.

(1) This property is a land-lease property.

20

Office Property Summary by Region - December 31, 2010 (continued)

Wholly Owned Properties

Operating Property Count		Submarket	Business Park	Year Built or Renovated	S or M	Total Operational Square Feet	Total Square Feet Under Construction / Redevelopment
	St. Mary’s & King George Counties
1	22309 Exploration Drive	St. Mary’s County	Exploration Park	1984/1997	M	98,860
2	22289 Exploration Drive	St. Mary’s County	Exploration Park	2000	M	58,676
3	22299 Exploration Drive	St. Mary’s County	Exploration Park	1998	M	58,363
4	22300 Exploration Drive	St. Mary’s County	Exploration Park	1997	M	44,830
						260,729	—
1	46579 Expedition Drive	St. Mary’s County	Expedition Park	2002	M	61,156
2	46591 Expedition Drive	St. Mary’s County	Expedition Park	2005-2006	M	59,483
						120,639	—
1	44425 Pecan Court	St. Mary’s County	Wildewood Tech Park	1997	M	58,981
2	44408 Pecan Court	St. Mary’s County	Wildewood Tech Park	1986	S	50,532
3	23535 Cottonwood Parkway	St. Mary’s County	Wildewood Tech Park	1984	M	46,656
4	44417 Pecan Court	St. Mary’s County	Wildewood Tech Park	1989	S	29,053
5	44414 Pecan Court	St. Mary’s County	Wildewood Tech Park	1986	S	25,444
6	44420 Pecan Court	St. Mary’s County	Wildewood Tech Park	1989	S	25,200
						235,866	—
1	16480 Commerce Drive	King George County	Dahlgren Technology Center	2000	M	70,728
2	16541 Commerce Drive	King George County	Dahlgren Technology Center	1996	S	36,053
3	16539 Commerce Drive	King George County	Dahlgren Technology Center	1990	S	32,076
4	16442 Commerce Drive	King George County	Dahlgren Technology Center	2002	S	25,518
5	16501 Commerce Drive	King George County	Dahlgren Technology Center	2002	S	22,833
6	16543 Commerce Drive	King George County	Dahlgren Technology Center	2002	S	17,370
						204,578	—
18	Total St. Mary’s & King George Counties					821,812	—
	Northern Virginia
1	15000 Conference Center Drive	Dulles South	Westfields Corporate Center	1989	M	471,440
2	15010 Conference Center Drive	Dulles South	Westfields Corporate Center	2006	M	223,610
3	15059 Conference Center Drive	Dulles South	Westfields Corporate Center	2000	M	145,224
4	15049 Conference Center Drive	Dulles South	Westfields Corporate Center	1997	M	145,706
5	14900 Conference Center Drive	Dulles South	Westfields Corporate Center	1999	M	126,158
6	14280 Park Meadow Drive	Dulles South	Westfields Corporate Center	1999	M	114,126
7	4851 Stonecroft Boulevard	Dulles South	Westfields Corporate Center	2004	M	88,094
8	14850 Conference Center Drive	Dulles South	Westfields Corporate Center	2000	M	72,194
9	14840 Conference Center Drive	Dulles South	Westfields Corporate Center	2000	M	69,710
						1,456,262	—
1	13200 Woodland Park Road	Herndon	Woodland Park	2002	M	404,665
1	13454 Sunrise Valley Road	Herndon	Dulles Tech	1998	M	111,816
2	13450 Sunrise Valley Road	Herndon	Dulles Tech	1998	M	53,776
						165,592	—
1	3120 Fairview Park Drive	Herndon	Fairview Park	2008	M	7,080	176,360
1	1751 Pinnacle Drive	Tysons Corner		1989/1995	M	260,469
2	1753 Pinnacle Drive	Tysons Corner		1976/2004	M	186,707
3	1550 Westbranch Drive	Tysons Corner		2002	M	152,240
						599,416	—
1	2900 Towerview Road	Route 28 South	Renaissance Park	1982/2008	M	139,802
17	Total Northern Virginia					2,772,817	176,360
	Other
1	11751 Meadowville Lane	Richmond Southwest	Meadowville Technology Park	2007	M	193,000
1	201 Technology Park Drive	Southwest Virginia	Russell Regional Business Tech Park	2007	S	102,842
2	Total Other					295,842	—

The S or M notation indicates single story or multi-story building, respectively.

21

Office Property Summary by Region - December 31, 2010 (continued)

Wholly Owned Properties

Operating Property Count		Submarket	Business Park	Year Built or Renovated	S or M	Total Operational Square Feet	Total Square Feet Under Construction / Redevelopment
	Greater Philadelphia
	755 Arbor Way	Blue Bell	Arborcrest	1992	S	—	418,430
1	785 Jolly Road	Blue Bell	Arborcrest	1996	M	219,065	—
2	801 Lakeview Drive	Blue Bell	Arborcrest	1994	M	156,695	61,958
	751 Arbor Way	Blue Bell	Arborcrest	1991	M	—	113,500
2	Total Greater Philadelphia					375,760	593,888
	San Antonio, Texas
2	7700 Potranco Road	San Antonio Northwest	Sentry Gateway	1982/1985	M	508,412
3	8000 Potranco Road	San Antonio Northwest	Sentry Gateway	2010	M	125,005
4	8030 Potranco Road	San Antonio Northwest	Sentry Gateway	2010	M	125,005
5	7700-5 Potranco-Warehouse	San Antonio Northwest	Sentry Gateway	2009	S	25,056
6	7700-1 Potranco Road	San Antonio Northwest	Sentry Gateway	2007	S	8,674
						792,152	—
1	1560 Cable Ranch Road - Building B	San Antonio Northwest	151 Technology Center	1985/2006	M	77,040
2	1560 Cable Ranch Road - Building A	San Antonio Northwest	151 Technology Center	1985/2007	M	45,935
						122,975	—
8	Total San Antonio, Texas					915,127	—
	Colorado Springs, Colorado
1	655 Space Center Drive	Colorado Springs East	Patriot Park	2008	M	103,970
2	985 Space Center Drive	Colorado Springs East	Patriot Park	1989	M	104,028
3	565 Space Center Drive	Colorado Springs East	Patriot Park	2009	M	89,899
4	745 Space Center Drive	Colorado Springs East	Patriot Park	2006	M	51,500
5	980 Technology Court	Colorado Springs East	Patriot Park	1995	S	33,207
6	525 Babcock Road	Colorado Springs East	Patriot Park	1967	S	14,000
						396,604	—
1	1055 North Newport Road	Colorado Springs East	Aerotech Commerce Park	2007-2008	M	59,763
1	3535 Northrop Grumman Point	Colorado Springs East	Colorado Springs Airport	2008	M	124,305
1	1670 North Newport Road	Colorado Springs East	Newport	1986-1987	M	67,500
2	1915 Aerotech Drive	Colorado Springs East		1985	S	37,946
3	1925 Aerotech Drive	Colorado Springs East		1985	S	37,946
						143,392	—
1	10807 New Allegiance Drive	I-25 North Corridor	InterQuest Office	2009	M	145,723
2	12515 Academy Ridge View	I-25 North Corridor	InterQuest Office	2006	M	61,372
3	9965 Federal Drive	I-25 North Corridor	InterQuest Office	1983/2007	M	74,749
4	9945 Federal Drive	I-25 North Corridor	InterQuest Office	2009	S	74,005
5	9950 Federal Drive	I-25 North Corridor	InterQuest Office	2001	S	66,223
6	9925 Federal Drive	I-25 North Corridor	InterQuest Office	2008	S	53,788
7	9960 Federal Drive	I-25 North Corridor	InterQuest Office	2001	S	46,948
						522,808	—
1	5775 Mark Dabling Boulevard	Colorado Springs Northwest	Northcreek	1984	M	109,678
2	5725 Mark Dabling Boulevard	Colorado Springs Northwest	Northcreek	1984	M	108,976
3	5755 Mark Dabling Boulevard	Colorado Springs Northwest	Northcreek	1989	M	103,400
						322,054	—
21	Total Colorado Springs, Colorado					1,568,926	—
	Washington, DC - Capitol Riverfront
1	1201 M Street	Washington, DC - Capitol Riverfront	Maritime Plaza	2001	M	200,509
2	1220 12th Street	Washington, DC - Capitol Riverfront	Maritime Plaza	2003	M	161,165
	Total Washington, D.C. - Capitol Riverfront					361,674	—

The S or M notation indicates single story or multi-story building, respectively.

22

Office Property Summary by Region - December 31, 2010 (continued)

Wholly Owned Properties

Operating Property Count		Submarket	Business Park	Year Built or Renovated	S or M	Total Operational Square Feet	Total Square Feet Under Construction / Redevelopment
	Suburban Maryland
1	11800 Tech Road	North Silver Spring	Montgomery Industrial	1989	M	228,179
1	400 Professional Drive	Gaithersburg	Crown Point	2000	M	129,355
1	110 Thomas Johnson Drive	Frederick		1987/1999	M	122,490
1	45 West Gude Drive	Rockville		1987	M	108,588
2	15 West Gude Drive	Rockville		1986	M	106,694
						215,282	—
5	Total Suburban Maryland					695,306	—
	Greater Baltimore
1	11311 McCormick Road	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1984/1994	M	214,704
2	200 International Circle	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1987	M	125,352
3	226 Schilling Circle	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1980	M	97,309
4	201 International Circle	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1982	M	78,243
5	11011 McCormick Road	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1974	M	57,104
6	216 Schilling Circle	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1988/2001	M	35,806
7	222 Schilling Circle	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1978/1997	M	28,618
8	224 Schilling Circle	Hunt Valley/Rte 83 Corridor	Hunt Valley Business Comm.	1978/1997	M	27,575
						664,711	—
1	10150 York Road	Hunt Valley/Rte 83 Corridor		1985	M	174,737
2	9690 Deereco Road	Hunt Valley/Rte 83 Corridor		1988	M	133,861
3	375 West Padonia Road	Hunt Valley/Rte 83 Corridor		1986	M	104,885
						413,483	—
1	7210 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1972	S	83,435
2	7152 Windsor Boulevard	Baltimore County Westside	Rutherford Business Center	1986	S	57,855
3	21 Governor’s Court	Baltimore County Westside	Rutherford Business Center	1981/1995	M	56,383
4	7125 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1985	M	50,604
5	7104 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1988	M	30,081
6	17 Governor’s Court	Baltimore County Westside	Rutherford Business Center	1981	S	14,454
7	15 Governor’s Court	Baltimore County Westside	Rutherford Business Center	1981	S	14,568
8	7127 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1985	S	11,630
9	7129 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1985	S	11,075
10	7108 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1988	S	8,811
11	7102 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1988	S	8,879
12	7106 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1988	S	8,899
13	7131 Ambassador Road	Baltimore County Westside	Rutherford Business Center	1985	S	7,734
						364,408	—
1	502 Washington Avenue	Towson		1984	M	90,435
2	102 West Pennsylvania Avenue	Towson		1968/2001	M	49,701
3	100 West Pennsylvania Avenue	Towson		1952/1989	M	20,099
4	109-111 Allegheny Avenue	Towson		1971	M	18,431
						178,666	—
1	1501 South Clinton Street	Baltimore	Canton Crossing	2006	M	474,637
1	209 Research Boulevard	Harford County	Northgate Business Park	2010	M	47,930	29,262
2	210 Research Boulevard	Harford County	Northgate Business Park	2010	M	27,551	52,022
						75,481	81,284
31	Subtotal (continued on next page)					2,171,386	81,284

The S or M notation indicates single story or multi-story building, respectively.

23

Office Property Summary by Region - December 31, 2010 (continued)

Wholly Owned Properties

Operating Property Count		Submarket	Business Park	Year Built or Renovated	S or M	Total Operational Square Feet	Total Square Feet Under Construction / Redevelopment
31	Subtotal (continued from prior page)					2,171,386	81,284
1	4940 Campbell Boulevard	White Marsh	Campbell Corporate Center	1990	M	50,415
1	8140 Corporate Drive	White Marsh	Corporate Place	2003	M	76,271
2	8110 Corporate Drive	White Marsh	Corporate Place	2001	M	79,091
						155,362	—
1	9910 Franklin Square Drive	White Marsh	Franklin Ridge	2005	S	57,812
2	9920 Franklin Square Drive	White Marsh	Franklin Ridge	2006	S	42,891
3	9930 Franklin Square Drive	White Marsh	Franklin Ridge	2001	S	39,750
4	9900 Franklin Square Drive	White Marsh	Franklin Ridge	1999	S	33,800
5	9940 Franklin Square Drive	White Marsh	Franklin Ridge	2000	S	32,242
						206,495	—
1	8020 Corporate Drive	White Marsh	McLean Ridge	1997	S	50,796
2	8094 Sandpiper Circle	White Marsh	McLean Ridge	1998	S	49,585
3	8098 Sandpiper Circle	White Marsh	McLean Ridge	1998	S	46,485
4	8010 Corporate Drive	White Marsh	McLean Ridge	1998	S	38,487
						185,353	—
1	5355 Nottingham Ridge Road	White Marsh	Nottingham Ridge	2005	S	35,930
2	5325 Nottingham Ridge Road	White Marsh	Nottingham Ridge	2002	S	35,678
						71,608	—
1	7941-7949 Corporate Drive	White Marsh	Tyler Ridge	1996	S	57,782
2	8007 Corporate Drive	White Marsh	Tyler Ridge	1995	S	41,799
3	8019 Corporate Drive	White Marsh	Tyler Ridge	1990	S	32,423
4	8013 Corporate Drive	White Marsh	Tyler Ridge	1990	S	29,995
5	8003 Corporate Drive	White Marsh	Tyler Ridge	1999	S	17,599
6	8015 Corporate Drive	White Marsh	Tyler Ridge	1990	S	15,669
7	8023 Corporate Drive	White Marsh	Tyler Ridge	1990	S	9,486
						204,753	—
1	5020 Campbell Boulevard	White Marsh	White Marsh Business Center	1986-1988	S	43,623
2	5024 Campbell Boulevard	White Marsh	White Marsh Business Center	1986-1988	S	33,710
3	5026 Campbell Boulevard	White Marsh	White Marsh Business Center	1986-1988	S	30,163
4	5022 Campbell Boulevard	White Marsh	White Marsh Business Center	1986-1988	S	26,748
						134,244	—
1	10001 Franklin Square Drive	White Marsh	White Marsh Commerce Center	1997	S	218,215
1	8114 Sandpiper Circle	White Marsh	White Marsh Health Center	1986	S	45,806
1	4979 Mercantile Road	White Marsh	White Marsh Hi-Tech Center	1985	S	51,198
2	4969 Mercantile Road	White Marsh	White Marsh Hi-Tech Center	1983	S	47,132
						98,330	—
1	7939 Honeygo Boulevard	White Marsh	White Marsh Professional Center	1984	M	28,208
2	8133 Perry Hall Boulevard	White Marsh	White Marsh Professional Center	1988	M	27,996
3	7923 Honeygo Boulevard	White Marsh	White Marsh Professional Center	1985	M	23,481
						79,685	—
1	8031 Corporate Drive	White Marsh		1988/2004	S	66,000
2	8615 Ridgely’s Choice Drive	White Marsh		2005	M	37,746
3	8029 Corporate Drive	White Marsh		1988/2004	S	25,000
						128,746	—
66	Total Greater Baltimore					3,750,398	81,284
251	TOTAL WHOLLY-OWNED OFFICE PROPERTY PORTFOLIO					19,990,288	971,947

The S or M notation indicates single story or multi-story building, respectively.

24

Property Summary by Region - December 31, 2010

Joint Venture Office Properties

Operating Property Count		Submarket	Business Park	Year Built or Renovated	S or M	Total Operational Square Feet	Total Square Feet Under Construction / Redevelopment
	Unconsolidated Joint Venture Office Properties
	Greater Harrisburg
1	2605 Interstate Drive	East Shore	Commerce Park	1990	M	79,456
2	2601 Market Place	East Shore	Commerce Park	1989	M	65,411
						144,867	—
1	6345 Flank Drive	East Shore	Gtwy Corp. Ctr.	1989	S	69,443
2	6340 Flank Drive	East Shore	Gtwy Corp. Ctr.	1988	S	68,200
3	6400 Flank Drive	East Shore	Gtwy Corp. Ctr.	1992	S	52,439
4	6360 Flank Drive	East Shore	Gtwy Corp. Ctr.	1988	S	46,589
5	6385 Flank Drive	East Shore	Gtwy Corp. Ctr.	1995	S	32,671
6	6380 Flank Drive	East Shore	Gtwy Corp. Ctr.	1991	S	32,668
7	6405 Flank Drive	East Shore	Gtwy Corp. Ctr.	1991	S	32,000
8	95 Shannon Road	East Shore	Gtwy Corp. Ctr.	1999	S	21,976
9	75 Shannon Road	East Shore	Gtwy Corp. Ctr.	1999	S	20,887
10	6375 Flank Drive	East Shore	Gtwy Corp. Ctr.	2000	S	19,783
11	85 Shannon Road	East Shore	Gtwy Corp. Ctr.	1999	S	12,863
						409,519	—
1	5035 Ritter Road	West Shore	Rossmoyne Bus. Ctr.	1988	S	56,556
2	5070 Ritter Road - Building A	West Shore	Rossmoyne Bus. Ctr.	1989	S	31,710
3	5070 Ritter Road - Building B	West Shore	Rossmoyne Bus. Ctr.	1989	S	28,347
						116,613	—
16	Total Greater Harrisburg					670,999	—
16	Total Unconsolidated Joint Venture Office Properties					670,999	—
	Consolidated Joint Venture Office Properties
	Suburban Maryland
1	5825 University Research Court	College Park	M Square Business Park	2008	M	118,528
2	5850 University Research Court	College Park	M Square Business Park	2009	M	123,464
						241,992	—
1	4230 Forbes Boulevard	Lanham	Forbes 50	2003	S	55,866
3	Total Suburban Maryland					297,858	—
	Baltimore/Washington Corridor
1	7740 Milestone Parkway	BWI Airport	Arundel Preserve	2009	M	143,939	—
	Total Baltimore/Washington Corridor					143,939	—
4	Total Consolidated Joint Venture Properties					441,797	—
20	TOTAL JOINT VENTURE OFFICE PROPERTY PORTFOLIO					1,112,796	—

The S or M notation indicates single story or multi-story building, respectively.

25

Property Occupancy Rates by Region by Quarter

Wholly Owned Office Properties

	Baltimore /								St. Mary’s &
	Washington		Northern		Greater		Suburban		King George		Colorado		San		Greater		Washington, DC -				Total
	Corridor		Virginia		Baltimore		Maryland		Counties		Springs		Antonio		Philadelphia		Capitol Riverfront		Other		Portfolio
December 31, 2010
Number of Buildings	111		17		66		5		18		21		8		2		2		2		252
Rentable Square Feet	8,432,626		2,772,817		3,750,398		695,306		821,812		1,568,926		915,127		375,760		361,674		295,842		19,990,288
Occupied %	89.5	%	91.9	%	85.0	%	71.4	%	86.8	%	76.2	%	100.0	%	100.0	%	98.5	%	100.0	%	88.2	%
Leased %	90.6	%	93.1	%	85.8	%	87.1	%	86.8	%	76.2	%	100.0	%	100.0	%	98.5	%	100.0	%	89.5	%
September 30, 2010
Number of Buildings	110		16		65		5		18		21		8		2		2		2		249
Rentable Square Feet	8,402,671		2,763,656		3,728,034		695,184		821,812		1,568,926		915,127		375,760		361,674		295,842		19,928,686
Occupied %	89.1	%	91.9	%	80.4	%	72.5	%	89.2	%	76.7	%	100.0	%	100.0	%	99.6	%	100.0	%	87.4	%
Leased %	90.3	%	93.2	%	83.5	%	73.3	%	89.7	%	76.7	%	100.0	%	100.0	%	99.6	%	100.0	%	88.7	%
June 30, 2010
Number of Buildings	109		16		64		5		18		21		6		4		—		4		247
Rentable Square Feet	8,168,938		2,764,708		3,687,629		695,184		821,812		1,571,462		665,117		615,397		—		497,042		19,487,289
Occupied %	89.6	%	96.0	%	81.2	%	70.7	%	96.0	%	75.1	%	100.0	%	100.0	%	0.0	%	100.0	%	88.3	%
Leased %	90.6	%	96.4	%	83.4	%	71.8	%	96.0	%	75.9	%	100.0	%	100.0	%	0.0	%	100.0	%	89.3	%
March 31, 2010
Number of Buildings	109		15		63		5		18		21		6		3		—		4		244
Rentable Square Feet	8,117,503		2,611,980		3,650,487		695,307		821,812		1,384,554		665,117		458,702		—		497,042		18,902,504
Occupied %	89.4	%	96.4	%	81.3	%	86.2	%	94.5	%	86.3	%	100.0	%	100.0	%	0.0	%	100.0	%	89.6	%
Leased %	90.8	%	96.8	%	81.4	%	86.2	%	94.5	%	86.3	%	100.0	%	100.0	%	0.0	%	100.0	%	90.3	%
December 31, 2009
Number of Buildings	109		15		64		5		18		21		6		3		—		4		245
Rentable Square Feet	8,277,178		2,613,077		3,672,756		695,307		821,812		1,384,554		665,117		458,702		—		497,042		19,085,545
Occupied %	91.6	%	96.6	%	80.3	%	91.9	%	97.8	%	85.8	%	100.0	%	100.0	%	0.0	%	100.0	%	90.7	%
Leased %	92.5	%	96.8	%	81.0	%	91.9	%	98.0	%	86.1	%	100.0	%	100.0	%	0.0	%	100.0	%	91.3	%

26

Property Occupancy Rates by Region by Quarter

Joint Venture Office Properties

	Unconsolidated		Consolidated
	Greater		Baltimore/Wash		Suburban		Total
	Harrisburg		Corridor		Maryland		Joint Ventures
December 31, 2010
Number of Buildings	16		1		3		20
Rentable Square Feet	670,999		143,939		297,858		1,112,796
Occupied %	74.3	%	6.0	%	88.3	%	69.2	%
Leased %	74.3	%	6.0	%	90.1	%	69.7	%
September 30, 2010
Number of Buildings	16		1		3		20
Rentable Square Feet	670,999		143,939		297,858		1,112,796
Occupied %	73.8	%	6.0	%	88.3	%	68.9	%
Leased %	73.8	%	6.0	%	90.1	%	69.4	%
June 30, 2010
Number of Buildings	16		1		3		20
Rentable Square Feet	670,999		143,939		297,858		1,112,796
Occupied %	76.4	%	6.0	%	86.2	%	69.9	%
Leased %	76.4	%	6.0	%	90.0	%	70.9	%
March 31, 2010
Number of Buildings	16		1		3		20
Rentable Square Feet	670,999		143,939		297,858		1,112,796
Occupied %	76.4	%	6.0	%	84.1	%	69.4	%
Leased %	76.4	%	6.0	%	90.1	%	71.0	%
December 31, 2009
Number of Buildings	16		1		3		20
Rentable Square Feet	670,999		143,939		297,866		1,112,804
Occupied %	79.0	%	6.0	%	84.1	%	70.9	%
Leased %	79.0	%	6.0	%	84.1	%	70.9	%

Reconciliation of Wholly Owned Properties to Entire

Portfolio as of December 31, 2010

		Square
	Count	Feet	Occupied %		Leased %
Wholly Owned Properties	252	19,990,288	88.2	%	89.5	%
Add: Consolidated Joint Venture Properties	4	441,797	61.5	%	62.7	%
Subtotal	256	20,432,085	87.6	%	88.9	%
Add: Unconsolidated Joint Venture Properties	16	670,999	74.3	%	74.3	%
Total Portfolio	272	21,103,084	87.2	%	88.5	%

27

Top Twenty Tenants of Wholly Owned Office Properties as of December 31, 2010 (1)

(Dollars in thousands)

				Percentage of		Total		Percentage		Weighted
			Total	Total		Annualized		of Total		Average
		Number of	Occupied	Occupied		Rental		Annualized Rental		Remaining
Tenant		Leases	Square Feet	Square Feet		Revenue (2) (3)		Revenue		Lease Term (4)
United States of America	(5)	74	3,133,808	17.8	%	$	95,049	21.1	%	6.2
Northrop Grumman Corporation	(6)	17	1,259,167	7.1	%	32,857		7.3	%	6.6
Booz Allen Hamilton, Inc.		8	726,070	4.1	%	21,311		4.7	%	4.5
Computer Sciences Corporation	(6)	6	612,024	3.5	%	18,788		4.2	%	3.1
ITT Corporation	(6)	9	333,169	1.9	%	8,095		1.8	%	4.1
The MITRE Corporation		4	260,348	1.5	%	8,044		1.8	%	5.8
The Aerospace Corporation	(6)	3	247,253	1.4	%	7,763		1.7	%	4.1
CareFirst, Inc.		2	221,893	1.3	%	7,661		1.7	%	5.8
Wells Fargo & Company	(6)	6	215,620	1.2	%	7,484		1.7	%	7.4
L-3 Communications Holdings, Inc.	(6)	4	256,120	1.5	%	7,484		1.7	%	3.3
Integral Systems, Inc.	(6)	4	241,627	1.4	%	6,205		1.4	%	9.1
Comcast Corporation	(6)	7	308,332	1.7	%	6,131		1.4	%	2.8
The Boeing Company	(6)	5	192,719	1.1	%	5,875		1.3	%	3.9
AT&T Corporation	(6)	5	321,063	1.8	%	5,490		1.2	%	7.8
Ciena Corporation		5	263,724	1.5	%	4,956		1.1	%	2.2
General Dynamics Corporation	(6)	5	174,719	1.0	%	4,679		1.0	%	2.7
Unisys Corporation		1	156,695	0.9	%	4,143		0.9	%	9.4
The Johns Hopkins Institutions	(6)	5	140,837	0.8	%	3,674		0.8	%	5.9
Merck & Co., Inc.	(6)	2	225,894	1.3	%	2,950		0.7	%	1.6
First Mariner Bank	(6)	2	75,461	0.4	%	2,929		0.7	%	5.7
Subtotal Top 20 Office Tenants		174	9,366,543	53.1	%	261,568		58.1	%	5.5
All remaining tenants		709	8,260,979	46.9	%	189,000		41.9	%	3.9
Total/Weighted Average		883	17,627,522	100.0	%	$	450,568	100.0	%	4.9

(1)	Table excludes owner occupied leasing activity which represents 170,855 square feet with total annualized rental revenue of $4.0 million and a weighted average remaining lease term of 4.9 years as of December 31, 2010.
(2)	Total Annualized Rental Revenue is the monthly contractual base rent as of December 31, 2010, multiplied by 12, plus the estimated annualized expense reimbursements under existing office leases.
(3)	Order of tenants is based on Total Annualized Rental Revenue.
(4)	The weighting of the lease term was computed using Total Rental Revenue.
(5)	Many of our government leases are subject to early termination provisions which are customary to government leases. The weighted average remaining lease term was computed assuming no exercise of such early termination rights.
(6)	Includes affiliated organizations or agencies.

28

Average Occupancy Rates by Region for Same Office Properties (1)

	Number	Rentable
	of	Square	Three Months Ended										Year Ended
	Buildings	Feet	12/31/10		9/30/10		6/30/10		3/31/10		12/31/09		12/31/10		12/31/09
Baltimore Washington Corridor	105	7,686,276	89.5	%	89.5	%	89.9	%	90.1	%	91.7	%	89.7	%	92.4	%
Northern Virginia	15	2,613,497	91.5	%	91.6	%	96.2	%	96.6	%	96.9	%	94.0	%	96.1	%
Greater Baltimore	62	3,164,350	81.3	%	79.9	%	80.2	%	79.7	%	78.8	%	80.3	%	81.7	%
Suburban Maryland	6	751,172	73.3	%	72.9	%	72.1	%	90.0	%	91.6	%	77.1	%	93.9	%
St.Mary’s and King George Counties	18	821,812	87.8	%	93.3	%	95.3	%	94.8	%	97.8	%	92.8	%	96.7	%
Colorado Springs	16	1,144,139	89.9	%	88.2	%	90.0	%	90.4	%	89.9	%	89.6	%	92.2	%
San Antonio	5	640,061	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%
Greater Philadelphia	1	219,065	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%
Other	2	295,842	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%	100.0	%
Total Office	230	17,336,214	88.2	%	88.1	%	89.2	%	90.1	%	90.9	%	88.9	%	91.7	%

(1)  Same office properties represent buildings owned and 100% operational since January 1, 2009.

29

Lease Expiration Analysis by Year for Wholly Owned Office Properties

As of December 31, 2010 (1)

Year and Region of Lease Expiration (2)	Number of Leases Expiring	Square Footage of Leases Expiring	Percentage of Period’s Expiring Square Feet		Percentage of Total Occupied Square Feet		Total Annualized Rental Revenue of Expiring Leases (3)		Percentage of Total Annualized Rental Revenue Expiring		Total Annual. Rental Revenue of Expiring Leases per Occupied Square Foot
							(000’s)
Baltimore/Washington Corridor	58	847,959	44.1	%	4.8	%	$	20,897	4.6	%	$	24.64
Northern Virginia	7	259,171	13.5	%	1.5	%	6,658		1.5	%	25.69
Greater Baltimore	66	382,761	19.9	%	2.2	%	7,758		1.7	%	20.27
Suburban Maryland	3	82,938	4.3	%	0.5	%	2,321		0.5	%	27.98
St. Mary’s and King George Cos.	12	122,061	6.4	%	0.7	%	2,416		0.5	%	19.79
Colorado Springs	7	137,298	7.1	%	0.8	%	2,508		0.6	%	18.27
Washington, DC-Capitol Riverfront	8	89,836	4.7	%	0.5	%	4,320		1.0	%	48.09
2011	161	1,922,024	100.0	%	10.9	%	46,878		10.4	%	24.39
Baltimore/Washington Corridor	48	1,166,419	45.5	%	6.6	%	30,370		6.7	%	26.04
Northern Virginia	18	165,006	6.4	%	0.9	%	4,911		1.1	%	29.76
Greater Baltimore	54	559,551	21.8	%	3.2	%	10,729		2.4	%	19.17
Suburban Maryland	2	18,423	0.7	%	0.1	%	323		0.1	%	17.53
St. Mary’s and King George Cos.	11	279,974	10.9	%	1.6	%	5,152		1.1	%	18.40
Greater Philadelphia	1	219,065	8.5	%	1.2	%	2,784		0.6	%	12.71
Colorado Springs	7	76,161	3.0	%	0.4	%	1,602		0.4	%	21.03
San Antonio	2	78,359	3.1	%	0.4	%	1,359		0.3	%	17.34
Washington, DC-Capitol Riverfront	1	1,608	0.1	%	0.0	%	76		0.0	%	47.26
2012	144	2,564,566	100.0	%	14.5	%	57,306		12.7	%	22.35
Baltimore/Washington Corridor	55	1,207,037	55.8	%	6.8	%	37,432		8.3	%	31.01
Northern Virginia	11	155,381	7.2	%	0.9	%	4,073		0.9	%	26.21
Greater Baltimore	43	426,226	19.7	%	2.4	%	8,181		1.8	%	19.19
Suburban Maryland	2	8,861	0.4	%	0.1	%	238		0.1	%	26.86
St. Mary’s and King George Cos.	7	109,245	5.0	%	0.6	%	1,882		0.4	%	17.23
Colorado Springs	8	126,189	5.8	%	0.7	%	2,478		0.5	%	19.64
Washington, DC-Capitol Riverfront	5	131,209	6.1	%	0.7	%	5,655		1.3	%	43.10
2013	131	2,164,148	100.0	%	12.3	%	59,939		13.3	%	27.70
Baltimore/Washington Corridor	43	704,524	37.6	%	4.0	%	19,490		4.3	%	27.66
Northern Virginia	7	445,617	23.8	%	2.5	%	14,178		3.1	%	31.82
Greater Baltimore	30	304,673	16.3	%	1.7	%	5,427		1.2	%	17.81
Suburban Maryland	5	129,865	6.9	%	0.7	%	2,663		0.6	%	20.51
St. Mary’s and King George Cos.	8	40,373	2.2	%	0.2	%	909		0.2	%	22.52
Colorado Springs	9	177,581	9.5	%	1.0	%	3,531		0.8	%	19.88
Washington, DC-Capitol Riverfront	6	71,562	3.8	%	0.4	%	3,039		0.7	%	42.47
2014	108	1,874,195	100.0	%	10.6	%	49,237		10.9	%	26.27
Baltimore/Washington Corridor	55	1,109,348	43.3	%	6.3	%	29,348		6.5	%	26.46
Northern Virginia	12	751,855	29.3	%	4.3	%	22,248		4.9	%	29.59
Greater Baltimore	35	367,935	14.4	%	2.1	%	6,605		1.5	%	17.95
Suburban Maryland	3	132,505	5.2	%	0.8	%	2,515		0.6	%	18.98
St. Mary’s and King George Cos.	8	76,744	3.0	%	0.4	%	1,281		0.3	%	16.69
Colorado Springs	8	95,106	3.7	%	0.5	%	1,796		0.4	%	18.88
Washington, DC-Capitol Riverfront	2	30,314	1.2	%	0.2	%	1,326		0.3	%	43.74
2015	123	2,563,807	100.0	%	14.5	%	65,119		14.5	%	25.40
Baltimore/Washington Corridor	78	2,460,746	39.2	%	14.0	%	63,118		14.0	%	25.65
Northern Virginia	20	635,232	10.1	%	3.6	%	19,856		4.4	%	31.26
Greater Baltimore	62	1,110,025	17.7	%	6.3	%	28,900		6.4	%	26.04
Suburban Maryland	3	121,672	1.9	%	0.7	%	3,057		0.7	%	25.12
St. Mary’s and King George Cos.	4	48,487	0.8	%	0.3	%	971		0.2	%	20.03
Greater Philadelphia	1	156,695	2.5	%	0.9	%	4,143		0.9	%	26.44
Colorado Springs	11	582,911	9.3	%	3.3	%	11,906		2.6	%	20.43
San Antonio	6	836,768	13.3	%	4.7	%	24,558		5.5	%	29.35
Washington, DC-Capitol Riverfront	2	28,367	0.5	%	0.2	%	1,163		0.3	%	41.00
Other	2	295,842	4.7	%	1.7	%	9,056		2.0	%	30.61
Thereafter	189	6,276,745	100.0	%	35.6	%	166,728		37.0	%	26.56
Other (4)	27	262,037	100.0	%	1.5	%	5,361		1.2	%	20.46
Total / Average	883	17,627,522			100.0	%	$	450,568	100.0	%	$	25.56

NOTE:  As of December 31, 2010, the weighted average lease term for the wholly owned office properties is 4.9 years.

(1)	This expiration analysis includes the effect of early renewals completed on existing leases but excludes the effect of new tenant leases on 266,125 square feet yet to commence as of December 31, 2010.
(2)	Many of our government leases are subject to certain early termination provisions which are customary to government leases. The year of lease expiration was computed assuming no exercise of such early termination rights.
(3)	Total Annualized Rental Revenue is the monthly contractual base rent as of December 31, 2010 multiplied by 12 plus the estimated annualized expense reimbursements under existing office leases.
(4)	Month-to-month leases and leases which have expired but the tenant remains in holdover are included in this line as the exact expiration date is unknown.

30

Renewal Analysis for Wholly Owned Operating Office Properties for Periods Ended December 31, 2010

	Baltimore/ Washington Corridor			Northern Virginia			Greater Baltimore			Suburban Maryland			St. Mary’s and King George Counties			Colorado Springs			Total Office
Quarter Ended December 31, 2010:
Expiring Square Feet	619,599			214,801			337,526			12,645			97,039			12,406			1,294,016
Vacated Square Feet	57,755			20,804			74,799			12,645			36,531			3,783			206,317
Renewed Square Feet	561,844			193,997			262,727			—			60,508			8,623			1,087,699
Retention Rate (% based upon square feet)	90.7		%	90.3		%	77.8		%	0.0		%	62.4		%	69.5		%	84.1		%
Renewed Space Only:
Average Committed Cost per Square Foot	$	9.38		$	6.00		$	7.38		$	—		$	7.27		$	3.13		$	8.13
Weighted Average Lease Term in years	4.1			2.9			3.6			—			1.5			2.9			3.6
Change in Total Rent - GAAP	4.8		%	-0.8		%	0.7		%	0.0		%	16.1		%	5.9		%	3.3		%
Change in Total Rent - Cash	-2.9		%	-6.5		%	-9.7		%	0.0		%	7.7		%	-1.2		%	-4.6		%
Renewed & Retenanted Space:
Average Committed Cost per Square Foot	$	9.58		$	7.92		$	12.17		$	58.10		$	11.49		$	3.13		$	14.02
Weighted Average Lease Term in years	4.1			3.1			5.2			11.3			2.1			2.9			4.7
Change in Total Rent - GAAP	4.7		%	-0.7		%	-4.5		%	30.5		%	15.3		%	5.9		%	3.7		%
Change in Total Rent - Cash	-3.1		%	-6.3		%	-13.8		%	16.5		%	5.6		%	-1.2		%	-4.5		%
Year Ended December 31, 2010:
Expiring Square Feet	1,647,618			776,759			647,422			290,780			232,998			129,598			3,725,175
Vacated Square Feet	459,076			227,613			156,453			199,597			115,779			31,128			1,189,646
Renewed Square Feet	1,188,542			549,146			490,969			91,183			117,219			98,470			2,535,529
Retention Rate (% based upon square feet)	72.1		%	70.7		%	75.8		%	31.4		%	50.3		%	76.0		%	68.1		%
Renewed Space Only:
Average Committed Cost per Square Foot	$	7.86		$	5.59		$	12.91		$	0.82		$	4.69		$	5.02		$	7.84
Weighted Average Lease Term in years	3.8			2.5			5.1			4.1			3.2			5.6			3.8
Change in Total Rent - GAAP	6.0		%	-2.9		%	3.0		%	0.1		%	16.3		%	-0.9		%	3.3		%
Change in Total Rent - Cash	-2.4		%	-8.8		%	-7.5		%	-9.7		%	5.2		%	-3.6		%	-4.8		%
Renewed & Retenanted Space:
Average Committed Cost per Square Foot	$	9.46		$	8.48		$	13.92		$	32.63		$	7.41		$	9.50		$	11.72
Weighted Average Lease Term in years	4.0			3.1			5.5			8.1			3.3			5.5			4.4
Change in Total Rent - GAAP	4.6		%	-3.1		%	-2.6		%	16.7		%	15.6		%	0.5		%	2.3		%
Change in Total Rent - Cash	-3.6		%	-8.9		%	-11.6		%	4.4		%	4.4		%	-2.8		%	-5.6		%

Notes:	No renewal or retenanting activity transpired in our San Antonio, Greater Philadelphia, Washington DC-Capital Riverfront, or Other regions.
	Activity is exclusive of owner occupied space and leases with less than a one-year term.
	Retention rate includes early renewals.

31

Office Property Development Summary as of December 31, 2010

(Dollars in thousands)

			Wholly Owned	Total		Percentage		as of December 31, 2010				Actual or Anticipated
Property and Location		Submarket	or Joint Venture (JV)	Rentable Square Feet		Leased as of 12/31/10		Anticipated Total Cost (1)		Cost to date		Construction Completion Date (2)	Anticipated Operational Date (3)
Under Construction
316 Sentinel Way (316 NBP) Annapolis Junction, Maryland		BWI Airport	Owned	125,044		0	%	28,124		21,464		1Q 11	1Q 12
7205 Riverwood Road Columbia, Maryland		Howard Co. Perimeter	Owned	86,000		0	%	18,900		4,154		4Q 11	4Q 12
Subtotal Government				211,044		0	%	$	47,024	$	25,618
% of Total Drivers				20	%
308 Sentinel Drive (308 NBP) Annapolis Junction, Maryland	(4)	BWI Airport	Owned	151,543		98	%	32,400		25,167		3Q 10	1Q 11
410 National Business Parkway Annapolis Junction, Maryland		BWI Airport	Owned	110,000		0	%	25,643		6,874		4Q 11	4Q 12
430 National Business Parkway Annapolis Junction, Maryland		BWI Airport	Owned	109,341		0	%	24,942		13,800		2Q 11	2Q 12
206 Research Boulevard Aberdeen, Maryland		Harford County	Owned	127,300		0	%	25,144		10,200		2Q 11	2Q 12
209 Research Boulevard Aberdeen, Maryland	(5)	Harford County	Owned	77,192		100	%	18,378		16,727		2Q 10	2Q 11
210 Research Boulevard Aberdeen, Maryland	(6)	Harford County	Owned	79,573		35	%	16,706		13,028		4Q 10	4Q 11
45310 Abell House Lane California, MD		St. Mary’s County	Owned	80,205		100	%	18,080		6,833		3Q 11	4Q 11
100 Sentry Gateway San Antonio, Texas		San Antonio Northwest	Owned	94,550		0	%	15,433		10,369		4Q 10	4Q 11
Subtotal Defense Information Technology				829,704		40	%	$	176,726	$	102,997
% of Total Drivers				80	%
Total Under Construction				1,040,748		32	%	$	223,750	$	128,615

	% of Total		Total Rentable	Percentage
Regions	Regions		Square Feet	Leased
Baltimore/Washington Corridor	56	%	581,928	25	%
Greater Baltimore	27	%	284,065	37	%
St. Mary’s County	8	%	80,205	100	%
San Antonio	9	%	94,550	0	%
Total Under Construction by Region	100	%	1,040,748	32	%

(1)	Anticipated Total Cost includes land, construction and leasing costs.
(2)	Actual or anticipated construction completion date is the estimated date of completion of the building shell.
(3)	Anticipated operational date is the estimated date when leases have commenced on 100% of a property’s space or one year from the cessation of major construction activities.
(4)	Although classified as “Under Construction,” 31,128 square feet are operational.
(5)	Although classified as “Under Construction,” 47,930 square feet are operational.
(6)	Although classified as “Under Construction,” 27,551 square feet are operational.

Demand Driver Categories (as classified by COPT management):

Defense Information Technology:  Development opportunity created through our current and future relationships with defense information technology contractors and, possibly, minor Government tenancy.

Government:  Development opportunity created through our existing and future relationship with various agencies of the government of the United States of America.  Excludes Government tenancy included in Defense Information Technology.

Market Demand:  Development opportunity created through perceived unfulfilled space requirements within a specific submarket; potential submarket demand exceeds existing supply.

Research Park:  Development opportunity created through specific research park relationship.

32

Office Property Development Summary as of December 31, 2010 (continued)

(Dollars in thousands)

Property and Location		Submarket	Wholly Owned or Joint Venture (JV)	Total Rentable Square Feet		Percentage Leased as of 12/31/10		Anticipated Total Cost (1)		Cost to date		Actual or Anticipated Construction Completion Date (2)	Anticipated Operational Date (3)
Redevelopment
7468 Candlewood Road Hanover, Maryland		BWI Airport	Owned	357,700		0	%	$	41,735	$	40,315	4Q 10	4Q 11
3120 Fairview Park Drive Herndon, Virginia	(4)	Herndon	Owned	183,440		4	%	57,800		43,100		4Q10	4Q11
801 Lakeview Drive (Lakeside I) Blue Bell, Pennsylvania	(5)	Greater Philadelphia	Owned	218,653		72	%	30,325		22,624		3Q 10	3Q 11
751 Arbor Way (Hillcrest I) Blue Bell, Pennsylvania		Greater Philadelphia	Owned	113,500		0	%	19,100		430		4Q11	4Q12
Total Redevelopment				873,293				$	148,960	$	106,469
Under Development
312 Sentinel Way Annapolis Junction, Maryland		BWI Airport	Owned	125,000				33,021		6,227		2Q12	2Q13
Subtotal Government				125,000				$	33,021	$	6,227
% of Total Drivers				9	%
310 Sentinel Way Annapolis Junction, Maryland		BWI Airport	Owned	240,000				66,960		3,461		1Q 13	1Q 14
420 National Business Parkway Annapolis Junction, Maryland		BWI Airport	Owned	140,000				35,400		3,943		1Q12	1Q13
202 Research Boulevard (Lot H) Aberdeen, Maryland		Harford County	Owned	127,530				27,600		4,151		2Q12	2Q13
7770 Backlick Road (Patriot Ridge I) Springfield, Virginia		Springfield	Owned	240,000				77,172		8,126		2Q 12	2Q 13
Sentry Gateway (Building 200) San Antonio, Texas		San Antonio Northwest	Owned	93,830				15,800		2,139		3Q 12	3Q 13
8100 Potranco Road San Antonio, Texas		San Antonio Northwest	Owned	125,000				24,400		3,324		4Q 12	3Q 13
Redstone Gateway (Building 1) Huntsville, Alabama		Huntsville	JV	115,000				21,650		700		4Q 11	4Q 12
Redstone Gateway (Building 2) Huntsville, Alabama		Huntsville	JV	120,000				23,830		400		2Q 12	2Q 13
Subtotal Defense Information Technology				1,201,360				$	292,812	$	26,243
% of Total Drivers				91	%
Total Under Development				1,326,360				$	325,833	$	32,470

	% of Total		Total Rentable
Regions	Regions		Square Feet
Baltimore/Washington Corridor	38	%	505,000
Greater Baltimore	10	%	127,530
Northern Virginia	18	%	240,000
San Antonio	16	%	218,830
Huntsville	18	%	235,000
Total Under Development by Region	100	%	1,326,360

(1)	Anticipated Total Cost includes land, construction and leasing costs, except for properties previously operated prior to placing into redevelopment, in which case only incremental costs of redevelopment are included.
(2)	Actual or anticipated construction completion date is the estimated date of completion of the building shell.
(3)	Anticipated operational date is the estimated date when leases have commenced on 100% of a property’s space or one year from the cessation of major construction activities.
(4)	This property was shell complete in 2008 and we acquired in December 2010. For accounting purposes, this space was 100% operational upon acquisition. For occupany reporting, we are including the space as “Under Redevelopment” until the earlier of when leases commence or one year from the date of acquisition.
(5)	Although classified as “Under Redevelopment”, 156,695 square feet are operational.

Demand Driver Categories (as classified by COPT management):

Defense Information Technology:  Development opportunity created through our current and future relationships with defense information technology contractors and, possibly, minor Government tenancy.

Government:  Development opportunity created through our existing and future relationship with various agencies of the government of the United States of America.  Excludes Government tenancy included in Defense Information Technology.

Market Demand:  Development opportunity created through perceived unfulfilled space requirements within a specific submarket; potential submarket demand exceeds existing supply.

Research Park:  Development opportunity created through a specific research park relationship.

33

Office Property Construction Placed into Service as of December 31, 2010 (1)

									Total
		Wholly	Total						Rentable
		Owned or	Rentable	Development Square Feet Placed Into Service					Square
		Joint Venture	Square		Year 2010				Feet
Property and Location	Submarket	(JV)	Feet	Year 2009	1st Quarter	2nd Quarter	3rd Quarter	4th Quarter	Leased
10807 New Allegiance Drive (Epic One) Colorado Springs, Colorado	I-25 North Corridor	Owned	145,723	46,765	—	98,958	—	—	59,993
565 Space Center Drive (Patriot Park) Colorado Springs, Colorado	Colorado Springs East	Owned	89,899	1,949	—	87,950	—	—	1,949
300 Sentinel Drive (300 NBP) Annapolis Junction, Maryland	BWI Airport	Owned	192,562	45,422	3,617	31,202	112,321	—	166,035
209 Research Boulevard Aberdeen, Maryland	Harford County	Owned	77,192	—	—	35,736	5,045	7,149	77,192
324 Sentinel Way (324 NBP) Annapolis Junction, Maryland	BWI Airport	Owned	125,118	—	—	—	125,118	—	125,118
8000 Potranco Road San Antonio, Texas	San Antonio Northwest	Owned	125,005	—	—	—	125,005	—	125,005
8030 Potranco Road San Antonio, Texas	San Antonio Northwest	Owned	125,005	—	—	—	125,005	—	125,005
210 Research Boulevard Aberdeen, Maryland	Harford County	Owned	79,573	—	—	—	—	27,551	27,551
308 Sentinel Drive (308 NBP) Annapolis Junction, Maryland	BWI Airport	Owned	151,543	—	—	—	—	31,128	148,486
Total Development Placed Into Service			1,111,620	94,136	3,617	253,846	492,494	65,828	856,334
									77	%

(1) Includes properties with space placed into service during the year ended December 31, 2010.

34

Office Property Construction Leasing as of December 31, 2010 (1)

		Wholly	Total
		Owned or	Rentable	Construction
		Joint Venture	Square	Commencement	Cumulative Square Feet Leased
Property and Location	Submarket	(JV)	Feet	Date	Year 2009		1st Quarter		2nd Quarter		3rd Quarter		4th Quarter
324 Sentinel Way (324 NBP) Annapolis Junction, Maryland	BWI Airport	Owned	125,118	1Q 09	—		125,118		125,118		125,118		125,118
5850 University Research Court College Park, Maryland	College Park	JV	123,464	3Q 08	123,464		123,464		123,464		123,464		123,464
8000 Potranco Road San Antonio, Texas	San Antonio Northwest	Owned	125,005	1Q 09	—		125,005		125,005		125,005		125,005
8030 Potranco Road San Antonio, Texas	San Antonio Northwest	Owned	125,005	1Q 09	—		125,005		125,005		125,005		125,005
Subtotal Government			498,592		123,464		498,592		498,592		498,592		498,592
					25	%	100	%	100	%	100	%	100	%
300 Sentinel Drive (300 NBP) Annapolis Junction, Maryland	BWI Airport	Owned	192,562	1Q 08	85,700		124,029		155,093		155,093		166,035
308 Sentinel Drive (308 NBP) Annapolis Junction, Maryland	BWI Airport	Owned	151,543	3Q 09	—		—		27,956		148,486		148,486
6721 Columbia Gateway Drive Columbia, Maryland	Howard Co. Perimeter	Owned	131,451	1Q 08	131,451		131,451		131,451		131,451		131,451
209 Research Boulevard Aberdeen, Maryland	Harford County	Owned	77,192	1Q 09	53,468		58,513		65,662		77,192		77,192
210 Research Boulevard Aberdeen, Maryland	Harford County	Owned	79,573	4Q 09	—		27,551		27,551		27,551		27,551
10807 New Allegiance Drive (Epic One) Colorado Springs, Colorado	I-25 North Corridor	Owned	145,723	2Q 08	46,765		59,993		59,993		59,993		59,993
565 Space Center Drive (Patriot Park) Colorado Springs, Colorado	Colorado Springs East	Owned	89,899	2Q 08	1,949		1,949		1,949		1,949		1,949
100 Sentry Gateway San Antonio, Texas	San Antonio Northwest	Owned	94,550	1Q 10	—		—		—		—		—
Subtotal Defense Information Technology			962,493		319,333		403,486		469,655		601,715		612,657
					33	%	42	%	49	%	63	%	64	%
Total Development Leasing			1,461,085		442,797		902,078		968,247		1,100,307		1,111,249
Percent Leased					30	%	62	%	66	%	75	%	76	%

(1) Includes properties with actual construction completion in 2009 or actual or anticipated construction completion in 2010.

35

Land Controlled as of December 31, 2010

Location	Submarket	Status	Acres		Estimated Developable Square Feet
National Business Park - North	BWI Airport	owned	162		1,111,000
1243 Winterson Road (AS 22)	BWI Airport	owned	2		30,000
940 Elkridge Landing Road (AS 7)	BWI Airport	owned	3		54,000
West Nursery Road	BWI Airport	owned	1		5,000
Arundel Preserve	BWI Airport	under contract/JV	56	up to	1,652,000
1460 Dorsey Road	BWI Airport	owned	6		60,000
Columbia Gateway Parcel T-11	Howard Co. Perimeter	owned	14		220,000
7125 Columbia Gateway Drive	Howard Co. Perimeter	owned	8		275,000
Riverwood	Howard Co. Perimeter	owned	5		27,000
Total Baltimore / Washington Corridor			257		3,434,000
Westfields Corporate Center	Dulles South	owned	23		400,000
Westfields - Park Center	Dulles South	owned	33		674,000
Woodland Park	Herndon	owned	5		225,000
Patriot Ridge	Springfield	owned	11		738,000
Total Northern Virginia			72		2,037,000
Canton Crossing	Baltimore	owned	10		773,000
White Marsh	White Marsh	owned	152		1,692,000
37 Allegheny Avenue	Towson	owned	0.3		40,000
North Gate Business Park	Harford County	owned	34		439,000
Total Greater Baltimore			196		2,944,000
Thomas Johnson Drive	Frederick	owned	6		170,000
Route 15 / Biggs Ford Road	Frederick	owned	107		1,000,000
Rockville Corporate Center	Rockville	owned	10		220,000
M Square Research Park	College Park	JV - 50% ownership	49		510,000
Total Suburban Maryland			172		1,900,000
Arborcrest	Blue Bell	owned	8		790,000
Total Greater Philadelphia			8		790,000
Dahlgren Technology Center	King George County	owned	39		122,000
Expedition VII	St. Mary’s County	owned	6		60,000
Total St. Mary’s & King George Counties			45		182,000
InterQuest	I-25 North Corridor	owned	113		1,623,000
9965 Federal Drive	I-25 North Corridor	owned	4		30,000
Patriot Park	Colorado Springs East	owned	71		756,000
Aerotech Commerce	Colorado Springs East	owned	6		90,000
Total Colorado Springs			194		2,499,000
Northwest Crossroads	San Antonio Northwest	owned	31		375,000
Military Drive	San Antonio Northwest	owned	37		658,000
Total San Antonio			68		1,033,000
Redstone Gateway	Huntsville, AL	JV- 85% ownership	458		4,360,000
Total Huntsville			458		4,360,000
Indian Head	Charles County, MD	JV- 75% ownership	192		967,000
Fort Ritchie (1)	Fort Ritchie	owned	591		1,700,000
Total Other			783		2,667,000
TOTAL			2,252		21,846,000

This land inventory schedule excludes all properties listed as under construction, redevelopment or under development as detailed on pages 32 and 33, and includes properties under ground lease to us.

(1)The Fort Ritchie acquisition includes 283,565 square feet of existing office space targeted for future redevelopment and 110 existing usable residential units.

36

Wholesale Data Center Summary as of December 31, 2010

(Dollars in thousands)

Actual or

Initial

Critical Load

Anticipated

Raised Floor

Stabilization

Upon

Anticipated

Construction

Anticipated

Gross Building

Square

Critical Load

Completion

MW

Total

Cost

Completion

Operational

Property and Location

Area

Footage (1)

(in MWs) (2)

Leased

Operational

Cost (3)

to date

Date (4)

Date (5)

Power Loft @ Innovation 9651 Hornbaker Road Manassas, Virginia

233,000

100,000

18

17

%

11

%

$

282,000

$

129,904

4Q 12

4Q 12

Lease Expiration Analysis

					Total
	Number				Annual Rental
	of Leases	Raised Floor	Critical Load	Critical Load	Revenue of
Year of Lease Expiration	Expiring	Square Footage	Leased (MW)	Used (MW)	Expiring Leases
2019	1	7,172	1	1	$	2,017
2020	1	12,773	2	1	1,900
			3	2	$	3,917

(1)  Raised floor square footage is that portion of the gross building area where tenants locate their computer servers. Raised floor area is considered to be the net rentable square footage.

(2)  Critical load is the power available for exclusive use of tenants in the property (expressed in terms of megawatts (“MWs”)).

(3)  Anticipated total cost includes land, construction and leasing costs.

(4)  Actual or anticipated construction completion date is the estimated date of completion of the building shell and equipment fit-out.

(5)  Anticipated operational date is the estimated date when leases have commenced on 100% of a property’s space or one year from the cessation of major construction activities.

37

Joint Venture Summary as of December 31, 2010

(Dollars in thousands)

Consolidated Ventures

	Joint Venture
	Interest							Consolidated
	Held By			Square		Total		Debt as
Property and Location	COPT		Status	Feet	Acreage	Assets (1)		of 12/31/10
4230 Forbes Boulevard Lanham, Maryland	50.0	%	Operating	55,866	5 acres	$	3,959	$	—
Indian Head Technology Center Business Park Indian Head, Maryland	75.0	%	Land Inventory	967,000	192 acres	7,452		—
7740-7744 Milestone Parkway Hanover, Maryland	50.0	%	Operating/ Land Inventory	447,539	23 acres	29,666		16,753
5825 University Research Court College Park, Maryland	50.0	%	Operating	118,528	8 acres	23,628		—
5850 University Research Court College Park, Maryland	50.0	%	Operating	123,464	8 acres	31,928		—
M Square Research Park College Park, Maryland	50.0	%	Land Inventory	510,000	49 acres	4,472		39,935
Redstone Gateway Huntsville, Alabama	85.0	%	Land Inventory	4,360,000	458 acres	19,353		—
TOTAL						$	120,458	$	56,688

Unconsolidated Ventures

	Joint Venture
	Interest							Off-Balance
	Held By			Square	COPT			Sheet Debt as
Property and Location	COPT		Status	Feet	Investment			of 12/31/10
Greater Harrisburg Portfolio Harrisburg and Mechanicsburg, Pennsylvania	20.0	%	Operating	670,999	$	(5,545	)	$	65,645

(1)Total assets includes any outside investment basis related to the applicable joint venture plus the total assets recorded on the books of the consolidated joint venture.

38