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                                                                    EXHIBIT 10.5

                               FOURTH AMENDMENT TO
                           SECOND AMENDED AND RESTATED
                        AGREEMENT OF LIMITED PARTNERSHIP
                      OF EOP OPERATING LIMITED PARTNERSHIP
         THIS FOURTH AMENDMENT TO SECOND AMENDED AND RESTATED AGREEMENT OF

LIMITED PARTNERSHIP OF EOP OPERATING LIMITED PARTNERSHIP (this "Amendment"),
dated December 22, 2000, as amended, is entered into by EQUITY OFFICE PROPERTIES
TRUST, a Maryland real estate investment trust, as the general partner (the
"General Partner") of EOP Operating Limited Partnership, a Delaware limited
partnership (the "Partnership"), for itself and on behalf of itself and the
Limited Partners of the Partnership, and those persons whose signatures are set
forth on the signature page attached hereto.

         WHEREAS, each of David A. Gardner ("GARDNER"), Donald J. Resnick
("RESNICK") and Mark D. Quigley ("QUIGLEY", and collectively with Gardner and
Resnick, the "CONTRIBUTING LIMITED PARTNERS") has previously received Class B
units of limited partnership interest in the Partnership (the "ORIGINAL OP
UNITS") in exchange for certain partnership interests (the "ORIGINAL PARTNERSHIP
INTERESTS") held directly or indirectly by the Contributing Limited Partners in
the partnerships identified in Exhibit "A" attached hereto (collectively, the
"ACORN PARTNERSHIPS");

         WHEREAS, on the date hereof, each of the Contributing Limited Partners
are receiving additional Class B Units of limited partnership interest in the
Partnership ("ADDITIONAL OP UNITS") in exchange for remaining partnership
interests (the "REMAINING PARTNERSHIP INTERESTS") in the Acorn Partnerships held
by Quigley and Acorn Associates, a New York general partnership of which Gardner
and Resnick are the sole partners, all pursuant to the Call Option Agreements
dated October 7, 1997 and November 21, 1997, each by and among Acorn Associates,
Quigley and the Partnership (collectively, the "CALL OPTION AGREEMENTS");

         WHEREAS, pursuant to the authority granted to the General Partner under
the Second Amended and Restated Agreement of Limited Partnership of EOP
Operating Limited Partnership dated as of June 19, 2000, as amended (the
"PARTNERSHIP AGREEMENT"), the General Partner desires to amend Exhibit A to the
Partnership Agreement to reflect the issuance of the Additional OP Units to the
Contributing Limited Partners; and

         WHEREAS, the Contributing Limited Partners desire to be bound by all of
the terms and conditions and other provisions of this Amendment and the
Partnership Agreement with respect to the Additional OP Units;

         NOW, THEREFORE, in consideration of the premises set forth above and
for other good and valuable consideration, the receipt and sufficiency of which
hereby are acknowledged, the General Partner hereby amends the Partnership
Agreement as follows:

         Exhibit A to the Partnership Agreement hereby is amended to reflect the
         issuance of the Additional OP Units to the Contributing Limited
         Partners. Exhibit "B" attached to this Amendment contains the name and
         address of, the number of Additional OP Units issued to, and the
         initial capital account of each Contributing Limited Partner, and the
         percentage interest of each such Contributing Limited Partner in the
         Partnership, and such Exhibit "B" shall be deemed attached to, and an
         addendum of, Exhibit A to the Partnership Agreement for all relevant
         purposes.



                                       2

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         All capitalized terms used in this Amendment and not otherwise defined
shall have the meanings assigned to them in the Partnership Agreement or the
Call Option Agreements, as applicable. Except as modified herein, all terms and
conditions of the Partnership Agreement shall remain in full force and effect,
which terms and conditions the General Partner hereby ratifies and affirms. Time
is of the essence of each and every provision of this Amendment.

         IN WITNESS WHEREOF, the undersigned has executed this Amendment as of
the date first set forth above.

                              EQUITY OFFICE PROPERTIES TRUST, a Maryland real
                              estate investment trust, the General Partner of
                              EOP Operating Limited Partnership and on behalf of
                              existing Limited Partners



                              By:    /s/ Stanley M. Stevens
                                 -----------------------------------------------
                              Name:  Stanley M. Stevens
                                   ---------------------------------------------
                              Title: Executive Vice President, Chief Legal
                                    --------------------------------------------
                                     Counsel and Secretary
                                    --------------------------------------------

AGREED AND ACKNOWLEDGED:

CONTRIBUTING LIMITED PARTNERS:


/s/ David A. Gardner
-----------------------------
DAVID A. GARDNER


/s/ Donald J. Resnick
-----------------------------
DONALD J. RESNICK


/s/ Mark D. Quigley
-----------------------------
MARK D. QUIGLEY


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                                   EXHIBIT "A"

                           LIST OF ACORN PARTNERSHIPS

EOP-Four Falls Corporate Center, L.P., a Pennsylvania limited partnership
formerly known as Four Falls Associates

EOP-Walnut Hill Plaza, L.P., a Pennsylvania limited partnership formerly known
as Walnut Hill Associates

EOP-Oak Hill Plaza, L.P., a Pennsylvania limited partnership formerly known as
Oak Hill Associates

EOP-One Valley Square, L.P., a Pennsylvania limited partnership formerly known
as Valley Square Associates

EOP-Two Valley Square, L.P., a Pennsylvania limited partnership formerly known
as Two Valley Square Associates

EOP-Three Valley Square, L.P., a Pennsylvania limited partnership formerly known
as Three Valley Square Associates

EOP-Four Valley Square, L.P., a Pennsylvania limited partnership formerly known
as Four Valley Square Associates

EOP-One Devon Square, L.P., a Pennsylvania limited partnership formerly known as
Devon Square Venture Partners

EOP-Two Devon Square, L.P., a Pennsylvania limited partnership formerly known as
Two Devon Square Associates

EOP-Three Devon Square, L.P., a Pennsylvania limited partnership formerly known
as Three Devon Square Associates




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                                   EXHIBIT "B"

                                                          ADDITIONAL OP UNITS(3)

-----------------

(3) All Class B units of limited partnership interest in the Partnership.

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<TABLE>
<CAPTION>

                                        NO. OF
   NAME AND ADDRESS OF              ADDITIONAL OP     INITIAL CAPITAL    PERCENTAGE
CONTRIBUTING LIMITED PARTNER           UNITS            ACCOUNT(4)        INTEREST(5)
----------------------------        -------------     ---------------    ----------
<S>                                 <C>               <C>                <C>



</TABLE>




---------------

(4) For purposes of this Exhibit "B" to this Amendment, the initial Capital
Account reflects the agreed value of the Remaining Partnership Interests
contributed to the Partnership, allocated per Additional OP Unit issued by the
Partnership in connection with such contribution. The initial Capital Account
set forth in this Exhibit "B" will be aggregated with the existing Capital
Account of each Contributing Limited Partner and, subsequently, will be
maintained in accordance with Exhibit B to the Partnership Agreement.

(5) For purposes of this Exhibit "B" to this Amendment, the Percentage Interest
reflects only the interests evidenced by the Additional OP Units received by the
Contributing Limited Partners in connection with the contribution of the
Remaining Partnership Interests, and is in addition to the interests evidenced
by the Original OP Units held by such Contributing Limited Partners in
connection with the contribution of the Original Partnership Interests.