2,000,000 Shares

CORPORATE OFFICE PROPERTIES TRUST

7.50% Series H Cumulative Redeemable Preferred Shares of Beneficial Interest
(Liquidation Preference $25.00 Per Share)
UNDERWRITING AGREEMENT

December 11, 2003

CREDIT SUISSE FIRST BOSTON LLC
WACHOVIA CAPITAL MARKETS, LLC
A.G. EDWARDS & SONS, INC.
LEGG MASON WOOD WALKER, INCORPORATED

C/O   CREDIT SUISSE FIRST BOSTON LLC,
Eleven Madison Avenue,
New York, N.Y. 10010-3629

And

WACHOVIA CAPITAL MARKETS, LLC
As Representatives of the several Underwriters
301 S. College Street
Charlotte, N.C. 28288

As Representatives of the several Underwriters

Dear Sirs:

1.     Introductory.  Corporate Office Properties Trust, a Maryland real estate investment trust (Company), proposes to issue and sell 2,000,000 (Offered Securities) of its 7.50% Series H Cumulative Redeemable Preferred Shares of Beneficial Interest (Liquidation Preference $25.00 Per Share), par value $.01 per share (the Series H Preferred Shares).  The Company and Corporate Office Properties, L.P., a Delaware limited partnership (Operating Partnership), hereby agree with the several Underwriters named in Schedule I hereto (Underwriters) as follows:

2.     Representations and Warranties of the Company and the Operating Partnership.  The Company and the Operating Partnership jointly and severally represent and warrant to, and agree with, the several Underwriters that:

(a)   A registration statement (No. 333-108785) relating to the Offered Securities being sold by the Company, including a base prospectus, has been filed with the Securities and Exchange Commission (the Commission) under the Securities Act of 1933, as amended (Act) and such registration statement (registration statement) has been declared effective.  For purposes of this Agreement, Effective Time means the date and time as of which the registration statement was declared effective by the Commission.  Effective Date with respect to the registration statement means the date of the Effective Time thereof.  The registration statement, as amended at its Effective Time, including all material incorporated by reference

therein, pursuant to the General Instructions of the Form on which it is filed and including all information (if any) deemed to be a part of the registration statement as of its Effective Time pursuant to Rule 430A(b) (Rule 430A(b)) under the Act, is hereinafter referred to as a Registration Statement.  Any Registration Statement filed by the Company pursuant to Rule 462(b) of the Act is hereinafter called the Rule 462(b) Registration Statement and from and after the date and time of filing the Rule 462(b) Registration Statement, the term Registration Statement shall include the Rule 462(b) Registration Statement.  The base prospectus, together with the final prospectus supplement setting forth the final terms of the offering, sale and plan of distribution of the Offered Securities, as filed with the Commission pursuant to and in accordance with Rule 424(b) (Rule 424(b)) under the Act and as included in the Registration Statement, including all material incorporated by reference in such prospectus, are hereinafter referred to as the Prospectus.  No document has been or will be prepared or distributed in reliance on Rule 434 under the Act.  The Company meets the requirements for the use of Form S-3 under the Act and the Registration Statement meets the requirements of, and complies in all material respects with, Rule 415(a)(1)(x) under the Act.

(b)   On the Effective Date of the Registration Statement and at the time the most recent Annual Report on Form 10-K was filed, the Registration Statement complied as to form in all material respects to the requirements of the Act and the rules and regulations of the Commission (Rules and Regulations) and did not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading and at the time of filing of the Prospectus pursuant to Rule 424(b) the Prospectus will comply as to form, in all material respects, to the requirements of the Act and the Rules and Regulations, and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading in light of the circumstances in which they were made.  The preceding sentence does not apply to statements in or omissions from a Registration Statement or the Prospectus based upon written information furnished to the Company by any Underwriter through Credit Suisse First Boston LLC and/or Wachovia Capital Markets, LLC (collectively, the Lead Underwriters) specifically for use therein, it being understood and agreed that the only such information is that described as such in Section 7(b) hereof.

(c)   No stop order suspending the effectiveness of the Registration Statement or any part thereof has been issued and, to the knowledge of the Company, no proceeding for that purpose has been instituted or threatened by the Commission or by the state securities authority of any jurisdiction.  No order preventing or suspending the use of the Prospectus has been issued and, to the knowledge of the Company, no proceeding for that purpose has been instituted or threatened by the Commission or by the state securities authority of any jurisdiction.

(d)   The Company has been duly organized and is an existing real estate investment trust in good standing under the laws of the State of Maryland, with power and authority as a real estate investment trust to own its properties and conduct its business as described in the Prospectus; and the Company is duly qualified to do business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to be so qualified would not reasonably be expected to have a material adverse effect on (i) the condition (financial or other), business, properties, prospects, net worth or results of operations of the Company and its Subsidiaries (as hereinafter defined) taken as a whole, (ii) the issuance or validity of the Offered Securities or (iii) the consummation of any of the transactions contemplated by this Agreement to be performed by the Company and/or the Subsidiaries (individually or collectively, a Material Adverse Effect).

EOP OPERATING LIMITED PARTNERSHIP
(a Delaware limited partnership)

$1,000,000,000

$800,000,000 4.65% Notes due 2010

Each Fully and unconditionally guaranteed by

EQUITY OFFICE PROPERTIES TRUST
(a Maryland real estate investment trust)

UNDERWRITING AGREEMENT

October 4, 2004

Citigroup Global Markets Inc.
388 Greenwich St., 32nd Floor
New York, NY 10013

Morgan Stanley & Co. Incorporated
1585 Broadway
New York, NY 10036

UBS Securities LLC
677 Washington Boulevard
Stamford, CT 06901

As Representatives of the several Underwriters named  . . .

EOP OPERATING LIMITED PARTNERSHIP
(a Delaware limited partnership)

$1,000,000,000

$800,000,000 4.65% Notes due 2010

Each Fully and unconditionally guaranteed by

EQUITY OFFICE PROPERTIES TRUST
(a Maryland real estate investment trust)

UNDERWRITING AGREEMENT

October 4, 2004

Citigroup Global Markets Inc.
388 Greenwich St., 32nd Floor
New York, NY 10013

Morgan Stanley & Co. Incorporated
1585 Broadway
New York, NY 10036

UBS Securities LLC
677 Washington Boulevard
Stamford, CT 06901

As Representatives of the several Underwriters named  . . .

EXECUTION VERSION

2,000,000 Shares

CORPORATE OFFICE PROPERTIES TRUST

Common Shares of Beneficial Interest
UNDERWRITING AGREEMENT

September 22, 2005

WACHOVIA CAPITAL MARKETS, LLC
301 S. College Street
Charlotte, N.C. 28288

Dear Sirs:

1.                                       Introductory.  Corporate Office Properties Trust, a  . . .

2,000,000 Shares

CORPORATE OFFICE PROPERTIES TRUST

Common Shares of Beneficial Interest
UNDERWRITING AGREEMENT

September 23, 2004

CREDIT SUISSE FIRST BOSTON LLC,
Eleven Madison Avenue,
New York, N.Y. 10010-3629

Dear Sirs:

1.                                       Introductory.  Corporate Office Properties Trust, a Maryland real estate  . . .

2,750,000 Shares

CORPORATE OFFICE PROPERTIES TRUST

Common Shares of Beneficial Interest
UNDERWRITING AGREEMENT

April 19, 2004

Wachovia capital Markets, LLC

301 S. College Street
Charlotte, N.C. 28288

Dear Sirs:

1.     Introductory.  Corporate Office Properties Trust, a Maryland real estate investment trust (�Company�), proposes to issue and sell to Wachovia Capital Markets, LLC (the �Underwriter�) 2,750,000 (�Firm Securities�) of its common shares of beneficial interest (the �Common Shares�), and also  . . .

2,000,000 Shares

CORPORATE OFFICE PROPERTIES TRUST

7.50% Series H Cumulative Redeemable Preferred Shares of Beneficial Interest
(Liquidation Preference $25.00 Per Share)
UNDERWRITING AGREEMENT

December 11, 2003

CREDIT SUISSE FIRST BOSTON LLC
WACHOVIA CAPITAL MARKETS, LLC
A.G. EDWARDS & SONS, INC.
LEGG MASON WOOD WALKER, INCORPORATED

C/O   CREDIT SUISSE FIRST BOSTON LLC,
Eleven Madison Avenue,
New York, N.Y. 10010-3629

And

WACHOVIA CAPITAL MARKETS, LLC
As Representatives of the several Underwriters
301 S. College  . . .