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                                 FIRST AMENDMENT
                                       TO
                           SECOND AMENDED AND RESTATED
                          LIMITED PARTNERSHIP AGREEMENT
                                       OF
                        CORPORATE OFFICE PROPERTIES, L.P.

         THIS FIRST AMENDMENT (the "Amendment") to the Second Amended and
Restated Limited Partnership Agreement of Corporate Office Properties, L.P., a
Delaware limited partnership (the "Partnership"), is made and entered into as of
December 21, 1999, by the undersigned.

                                    RECITALS

         A. The Partnership is a limited partnership organized under the
Delaware Revised Uniform Limited Partnership Act and governed by that certain
Seconded Amended and Restated Limited Partnership Agreement dated as of December
7, 1999 (the "Partnership Agreement").

         B. The sole general partner of the Partnership is Corporate Office
Properties Trust, a real estate investment trust formed under the laws of the
State of Maryland (the "General Partner").

         C. Pursuant to Section 11.1(B) of the Partnership Agreement, the
General Partner desires to correct certain provisions of the Partnership
Agreement which are ambiguous and conflict with other provisions of the
Partnership Agreement.

         NOW THEREFORE, the General Partner, intending to be legally bound,
hereby amends the Partnership Agreement as follows, effective as of the date set
forth above.

         1. The foregoing recitals to this Amendment are hereby incorporated in
and made a part of this Amendment. Capitalized terms used in this Amendment not
defined herein shall have the meaning set forth in the Partnership Agreement.

         2. Section 1.1 of the Partnership Agreement is amended by (i) deleting
the term "Redemption Rights," which such term was erroneously included in the
Partnership Agreement, (ii) adding the defined term "Redemption Ratio,"
initially equal to 1.0 and subject to anti-dilution adjustment, for the purpose
of redeeming Partnership Units for REIT Shares, which such concept was
erroneously deleted from the Partnership Agreement, and (iii) amending and
restating the terms "Share Payment" and "Unit Value" in order to (A) substitute
the new term "Redemption Ratio" for the incorrectly used term "Conversion
Factor" and (B) correct the "Share Payment" term by adding a fractional share
provision, as follows:

                  "REDEMPTION RATIO: The ratio (carried out to four decimal
                  places) applied when redeeming Partnership Units for REIT
                  Shares, which shall initially be 1.0. In the event that on or
                  after the date of this Agreement the General Partner (i)
                  declares or pays a dividend on its outstanding REIT Shares in
                  REIT Shares or makes a

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                  distribution to all holders of its outstanding REIT Shares in
                  REIT Shares, (ii) subdivides its outstanding REIT Shares or
                  (iii) combines its outstanding REIT Shares into a smaller
                  number of REIT Shares, the Redemption Ratio shall be adjusted
                  by multiplying the Redemption Ratio by a fraction, the
                  numerator of which shall be the number of REIT Shares issued
                  and outstanding on the record date (assuming for such purposes
                  that such dividend, distribution, subdivision or combination
                  has occurred as of such time), and the denominator of which
                  shall be the actual number of REIT Shares (determined without
                  the above assumption) issued and outstanding on the record
                  date for such dividend, distribution, subdivision or
                  combination. In the event that the Partnership (a) declares or
                  pays a distribution on the outstanding Partnership Units or
                  makes a distribution to all Partners in Partnership Units, (b)
                  subdivides the outstanding Partnership Units or (c) combines
                  the outstanding Partnership Units into a smaller number of
                  Partnership Units, the Redemption Ratio shall be adjusted by
                  multiplying the Redemption Ratio by a fraction, the numerator
                  of which shall be the actual number of Partnership Units
                  issued and outstanding on the record date (determined without
                  giving effect to such dividend, distribution, subdivision or
                  combination), and the denominator of which shall be the actual
                  member of Partnership Units (determined after giving effect to
                  such dividend, distribution, subdivision or combination)
                  issued and outstanding on such record date. Any adjustment to
                  the Redemption Ratio shall become effective immediately after
                  the effective date of such event retroactive to the record
                  date, if any, for such event.

                  SHARE PAYMENT: The payment to a Redeeming Party of a number of
                  REIT Shares determined by multiplying (i) the number of
                  Partnership Units tendered for redemption by such Redeeming
                  Party pursuant to a validly proffered Redemption Notice by
                  (ii) the Redemption Ratio. In the event the General Partner
                  grants any REIT Share Rights on or after the date of this
                  Agreement and prior to such payment, any Share Payment shall
                  include for the Redeeming Party such Redeeming Party's ratable
                  share of such REIT Share Rights other than REIT Share Rights
                  which have expired. In any case in which the Share Payment
                  would result in the issuance of a fractional REIT Share, the
                  General Partner shall pay the converting Redeeming Party cash
                  in lieu of issuance of a fractional REIT Share, with the value
                  of such fractional interest being determined by reference to
                  the Unit Value applicable on the Redemption Date.

                  UNIT VALUE: With respect to any Partnership Unit, the average
                  of the daily market price for a REIT Share for the ten (10)
                  consecutive trading days immediately preceding the date of
                  receipt of a Redemption Notice by the General Partner
                  multiplied by the Redemption Ratio. If the REIT Shares are
                  traded on a securities exchange or the NASDAQ Small Cap Market
                  or National Market System, the market price for each such
                  trading day shall be the reported last sale price on such day
                  or, if no sales take place on such day, the average of the
                  closing bid and asked prices on such day. If the REIT Shares
                  are not traded on a securities exchange or the NASDAQ Small
                  Cap Market or National Market System, the market price for
                  each such trading day shall be determined by the


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                  General Partner using any reasonable method of valuation. If a
                  Share Payment would include any REIT Share Rights, the value
                  of such REIT Share Rights shall be determined by the General
                  Partner using any reasonable method of valuation, taking into
                  account the Unit Value determined hereunder and the factors
                  used to make such determination and the value of such REIT
                  Share Rights shall be included in the Unit Value."

      3. Section 9.1(A) of the Partnership Agreement is amended and restated in
order to delete the sole use in the Partnership Agreement of the term
"Redemption Rights," as follows:

                  "(A) Subject to compliance with (v) the Act, (w) the terms and
                  conditions of the REIT Charter, (x) all requirements under the
                  Code applicable to real estate investment trusts, (y) Title 8
                  of the Corporations and Associations Article of the Annotated
                  Code of Maryland, as amended, or any other law as in effect
                  from time to time and (z) any applicable rule or policy of any
                  stock exchange or self-regulatory organization (a "Redemption
                  Restriction"), except if prohibited by other contractual
                  obligations, during each Redemption Period each Redeeming
                  Party shall have the right to redeem its Partnership Units by
                  providing the General Partner with a Redemption Notice. A
                  Limited Partner may invoke its rights under this Article IX
                  with respect to one or more Partnership Units or all of the
                  Partnership Units held by such Limited Partner. Upon the
                  General Partner's receipt of a Redemption Notice from a
                  Redeeming Party, the Partnership shall be obligated (subject
                  to the existence of any Redemption Restriction) to redeem the
                  Partnership Units from such Redeeming Party (the "Redemption
                  Obligation")."

      4. Section 9.3 of the Partnership Agreement is amended and restated in
order to delete the incorrect use of the term "Conversion Ratio," as follows:

                  "SECTION 9.3 REDEMPTION PRICE. On or before the Redemption
                  Date, the Partnership (or the General Partner if it elects
                  pursuant to Section 9.4) shall deliver to the Redeeming Party,
                  in the sole and absolute discretion of the General Partner,
                  either (i) a Share Payment or (ii) a Cash Payment; provided,
                  however, that a Share Payment shall not be made, and a Cash
                  Payment shall instead be made in all cases, if, in the sole
                  and absolute discretion of the General Partner, the making of
                  a Share Payment would result in a material risk of termination
                  of the General Partner's status as a REIT under the Code. In
                  order to enable the Partnership to effect a redemption by
                  making a Share Payment pursuant to this Section 9.3, the
                  General Partner in its sole and absolute discretion may issue
                  to the Partnership the number of REIT Shares required to make
                  such Share Payment in exchange for the issuance to the General
                  Partner of Partnership Units equal in number to the quotient
                  of the number of REIT Shares issued divided by the Redemption
                  Ratio. Any such Partnership Unit redeemed by the Redeeming
                  Party shall be deemed canceled."



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         In witness whereof, the General Partner has executed this Amendment as
of the day and year first above written.

                                       CORPORATE OFFICE PROPERTIES TRUST, a
                                       Maryland Real Estate Investment Trust

                                       By: /s/ ROGER A. WAESCHE, JR.
                                          -------------------------------------
                                       Name: Roger A. Waesche, Jr.
                                       Its:  Senior Vice President



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