<PAGE>

                                                                    Exhibit 10.1

                                FIRST AMENDMENT

     This First Amendment (the "Amendment") is made and entered into as of the
____ day of ___________, 2000, by and between EOP-Columbia Center, L.L.C., a
Delaware limited liability company ("Landlord"), and Avenue A, Inc., a
Washington corporation  ("Tenant").

                                   WITNESSETH

A.   WHEREAS, Landlord and Tenant are parties to that certain lease dated the
     23rd day of February, 2000, for space currently containing approximately
     23,751 rentable square feet (the "Original Premises") described as Suite
     No. 2600 on the 26th floor of the building commonly known as Bank of
     America Tower and the address of which is 701 Fifth Avenue, Seattle,
     Washington 98104 (the "Building"), which lease has not been previously
     amended or assigned (the "Lease"); and

B.   WHEREAS, Tenant has requested that additional space known as Suite 2510
     containing approximately 7,131 rentable square feet on the 25th floor of
     the Building shown on Exhibit A hereto (the "Suite 2510 Expansion Space"),
     be added to the Premises and that the Lease be appropriately amended and
     Landlord is willing to do the same on the terms and conditions set forth
     below, and

C.   WHEREAS, Tenant has requested that 8,476 rentable square feet of additional
     space known as (a) Suite 2020 containing approximately 3,642 rentable
     square feet on the 20th floor of the Building shown on Exhibit A hereto
     (the "Suite 2020 Expansion Space"), and (b) Suite 2054 containing
     approximately 4,834 rentable square feet on the 20th floor of the Building
     shown on Exhibit A hereto (the "Suite 2054 Expansion Space"), which spaces
     may be hereinafter collectively referred to as the "Temporary Expansion
     Space I", be temporarily added to the Premises and that the Lease be
     appropriately amended and Landlord is willing to do the same on the terms
     and conditions set forth below; and

D.   WHEREAS, Tenant has requested that additional space known as Suite 1400
     containing approximately 22,986 rentable square feet on the 14th floor of
     the Building shown on Exhibit A hereto (the "Temporary Expansion Space
     II"), be temporarily added to the Premises and that the Lease be
     appropriately amended and Landlord is willing to do the same on the terms
     and conditions set forth below (the Suite 2510 Expansion Space, Temporary
     Expansion Space I, and Temporary Expansion Space II are referred to herein
     collectively as "Expansion Spaces" and individually as "Expansion Space";
     additionally, the Temporary Expansion Space I, and the Temporary Expansion
     Space II are herein sometimes referred to collectively as the "Temporary
     Expansion Spaces" or generally and individually as a "Temporary Expansion
     Space"); and

E.   WHEREAS, the Lease by its terms shall expire on December 31, 2000 ("Prior
     Termination Date"), and the parties desire to extend the Term, all on the
     terms and conditions set forth below;


     NOW, THEREFORE, in consideration of the mutual covenants and agreements
     herein contained and other good and valuable consideration, the receipt and
     sufficiency of which are hereby acknowledged, Landlord and Tenant agree as
     follows:

I.   Expansion I.  Effective as of the Expansion Effective Date (as hereinafter
     defined), the Premises, as defined in the Lease, is increased from 23,751
     rentable square feet on the 26th floor to 39,358 rentable square feet on
     the 26th, 20th and 25th floors by the addition of the Temporary Expansion
     Space I and the Suite 2510 Expansion Space, and from and after the
     Expansion Effective Date, the Original Premises, the Suite 2510 Expansion
     Space, and the Temporary Expansion Space I, collectively, shall be deemed
     the Premises, as defined in the Lease. The Term for the Suite 2510
     Expansion Space shall commence on the Expansion Effective Date and end on
     the Extended Termination Date (defined below).  The Term for the Temporary
     Expansion Space I shall commence on the Expansion Effective Date and end on
     December 31, 2001 (the "Temporary Expansion Space  Termination Date").
     Tenant's occupancy of the Suite 2510 Expansion Space and the Temporary
     Expansion Space I are subject to all the terms and conditions of the Lease
     except as expressly modified herein and except that Tenant shall not be
     entitled to receive any allowances, abatements or other financial
     concessions granted with respect to the Original Premises unless such
     concessions are expressly provided for herein with respect to the Suite
     2510 Expansion Space or the Temporary Expansion Space I.
<PAGE>

     A.   The Expansion Effective Date shall be June 1, 2000, or upon Tenant's
          earlier occupancy of the Suite 2510 Expansion Space and/or the
          Temporary Expansion Space I.

     B.   The Expansion Effective Date shall be delayed to the extent that
          Landlord fails to deliver possession of the Suite 2510 Expansion Space
          or the Temporary Expansion Space I for any reason, including but not
          limited to, holding over by prior occupants.  Any such delay in the
          Expansion Effective Date shall not subject Landlord to any liability
          for any loss or damage resulting therefrom.  If the Expansion
          Effective Date is delayed, the Extended Termination Date shall not be
          similarly extended.

II.  Expansion II.  Effective as of the Temporary Expansion Space II Expansion
     Effective Date (as hereinafter defined), the Premises, as defined in the
     Lease, is increased from 39,358 rentable square feet on the 26th, 20th and
     25th floors to 62,344 rentable square feet on the 26th, 20th, 25th, and
     14th floors by the addition of the Temporary Expansion Space II, and from
     and after the Temporary Expansion Space II Expansion Effective Date, the
     Premises and Temporary Expansion Space II, collectively, shall be deemed
     the Premises, as defined in the Lease.  The Term for the Temporary
     Expansion Space II shall commence on the Temporary Expansion Space II
     Expansion Effective Date and end on the Temporary Expansion Space
     Termination Date. Tenant's occupancy of the Temporary Expansion Space II
     is  subject to all the terms and conditions of the Lease except as
     expressly modified herein and except that Tenant shall not be entitled to
     receive any allowances, abatements or other financial concessions granted
     with respect to the Original Premises unless such concessions are expressly
     provided for herein with respect to the Temporary Expansion Space II.

     A.   The Temporary Expansion Space II Expansion Effective Date shall be
          November 1, 2000, or upon such earlier date as Landlord can deliver
          the Temporary Expansion Space II free of the occupancy of the previous
          tenant.

     B.   The Temporary Expansion Space II Expansion Effective Date shall be
          delayed to the extent that Landlord fails to deliver possession of the
          Temporary Expansion Space II for any reason, including but not limited
          to, holding over by prior occupants.  Any such delay in the Temporary
          Expansion Space II Expansion Effective Date shall not subject Landlord
          to any liability for any loss or damage resulting therefrom.  If the
          Temporary Expansion Space II Expansion Effective Date is delayed, the
          Temporary Expansion Space Termination Date shall not be similarly
          extended.

III. Extension.  The Term is hereby extended for a period of 36 months and
     shall expire on December 31, 2003 ("Extended Termination Date"), unless
     sooner terminated in accordance with the terms of the Lease.  That portion
     of the Term commencing the day immediately following the Prior Termination
     Date ("Extension Date") and ending on the Extended Termination Date shall
     be referred to herein as the "Extended Term".

IV.  Monthly Base Rent.
     -----------------

     A.   Original Premises Through Prior Termination Date.  The Base Rent,
          Additional Rent and all other charges under the Lease shall be payable
          as provided therein with respect to the Original Premises through and
          including the Prior Termination Date.

     B.   Original Premises From and After Extension Date.  As of the Extension
          Date, the schedule of monthly installments of Base Rent payable with
          respect to the Original Premises during the Extended Term is the
          following:

          Tenant shall pay Landlord the sum of Two Million Eight Hundred
          Fourteen Thousand Four Hundred Ninety-Three and 68/100 Dollars
          ($2,814,493.68) as Base Rent for the Original Premises during the
          Extended Term in thirty-six (36) equal monthly installments of
          Seventy-Eight Thousand One Hundred Eighty and 38/100 Dollars
          ($78,180.38) each payable on or before the first day of each month
          during the period beginning January 1, 2001, and ending December 31,
          2003.

     C.   Suite 2510 Expansion Space from Expansion Effective Date through
          Extended Termination Date.  As of the Expansion Effective Date, the
          schedule of monthly installments of Base Rent payable with respect to
          the Suite 2510

                                       2
<PAGE>

          Expansion Space for the balance of the original Term and the Extended
          Term is the following:

          Tenant shall pay Landlord the sum of One Million One Nine Thousand
          Three Hundred Thirty-Three and 84/100 Dollars ($1,009,333.84) as Base
          Rent for the Suite 2510 Expansion Space for the balance of the
          original Term and the entirety of Extended Term in forty-three (43)
          equal monthly installments of Twenty-Three  Thousand Four Hundred
          Seventy-Two and 88/100 Dollars ($23,472.88) each payable on or before
          the first day of each month during the period beginning June 1, 2000,
          and ending December 31,  2003.

     D.   Temporary Expansion Space I From Expansion Effective Date Through
          Temporary Expansion Space Termination Date.  As of the Expansion
          Effective Date, the schedule of monthly installments of Base Rent
          payable with respect to the Temporary Expansion Space I for the
          balance of the original Term and through the Temporary Expansion Space
          Termination Date is the following:

          Tenant shall pay Landlord the sum of Five Hundred Sixteen Thousand Six
          Hundred Eighty-Two and 77/100 Dollars ($516,682.77) as Base Rent for
          the balance of the original Term and through the Temporary Expansion
          Space Termination Date in nineteen (19) equal monthly installments of
          Twenty-Seven Thousand One Hundred Ninety-Three and 83/100 Dollars
          ($27,193.83) each payable on or before the first day of each month
          during the period beginning June 1, 2000, and ending December 31,
          2001.

     E.   Temporary Expansion Space II From Temporary Expansion Space II
          Expansion Effective Date Through Temporary Expansion Space Termination
          Date.  As of the Temporary Expansion Space II Expansion Effective
          Date, the schedule of monthly installments of Base Rent payable with
          respect to the Temporary Expansion Space II for the balance of the
          original Term and through the Temporary Expansion Space Termination
          Date is the following:

          Tenant shall pay Landlord the sum of One Million Thirty-Two Thousand
          Four Hundred Fifty-Four and 50/100 Dollars ($1,032,454.50) as Base
          Rent for the balance of the original Term and through the Temporary
          Expansion Space Termination Date in fourteen (14) equal monthly
          installments of Seventy-Three Thousand Seven Hundred Forty-Six and
          75/100 Dollars ($73,746.75) each payable on or before the first day of
          each month during the period beginning November 1, 2000, and ending
          December 31, 2001.

     All such Base Rent shall be payable by Tenant in accordance with the terms
     of Article IV of the Lease.

V.   Additional Security Deposit.  Upon Tenant's execution hereof, Tenant shall
     pay $350,758.29 to Landlord which is added to and becomes part of the
     Security Deposit, if any, held by Landlord as provided under the Lease as
     security for payment of Rent and the performance of other terms and
     conditions of the Lease by Tenant.  Accordingly, simultaneous with the
     execution hereof, the Security Deposit is increased from $54,429.38 to
     $405,187.67.

VI.  Tenant's Pro Rata Share.  For the period commencing with the applicable
     Expansion Effective Date for each of the Expansion Spaces described herein
     and ending on the Extended Termination Date, with respect to the Suite 2510
     Expansion Space, and the Temporary Expansion Space Termination Date, with
     respect to each of the Temporary Expansion Spaces, Tenant's Pro Rata Share
     for each of the Expansion Spaces is as follows:

     A.   Suite 2510 Expansion Space:    four thousand eight hundred fifty-five
          ten-thousandths percent (0.4855%) (7,131 SF/1,468,858 SF).

     B.   Suite 2020 Expansion Space:    two thousand four hundred seventy-nine
          ten-thousandths percent (0.2479%) (3,642 SF/1,468,858 SF).

     C.   Suite 2054 Expansion Space:    three thousand two hundred ninety-one
          ten-thousandths percent (0.3291%) (4,834 SF/1,468,858 SF).

     D.   Temporary Expansion Space II:    one and five thousand six hundred
          forty-nine ten-thousandths percent (1.5649%) (22,986 SF/1,468,858 SF).

                                       3
<PAGE>

VII.  Expense Excess and Tax Excess.
      -----------------------------

     A.   Original Premises for the Extended Term.   For the period commencing
          with the Extension Date and ending on the Extended Termination Date,
          Tenant shall pay for its Pro Rata Share of Expense Excess and Tax
          Excess applicable to the Original Premises in accordance with the
          terms of the Lease.

     B.   Suite 2510 Expansion Space From Expansion Effective Date Through
          Extended Termination Date.  For the period commencing with the
          Expansion Effective Date and ending on the Extended Termination Date,
          Tenant shall pay for its Pro Rata Share of Expense Excess and Tax
          Excess applicable to the Suite 2510 Expansion Space in accordance with
          the terms of the Lease, provided, however, during such period, the
          Base Year for the computation of Tenant's Pro Rata Share of Expenses
          and Taxes applicable to the Suite 2510 Expansion Space is 2000.

     C.   Temporary Expansion Space I From Expansion Effective Date Through the
          Temporary Expansion Space Termination Date.  For the period commencing
          with the Expansion Effective Date and ending on the Temporary
          Expansion Space Termination Date, Tenant shall pay for its Pro Rata
          Share of Expense Excess and Tax Excess applicable to the Temporary
          Expansion Space I in accordance with the terms of the Lease, provided,
          however, during such period, the Base Year for the computation of
          Tenant's Pro Rata Share of Expenses and Taxes applicable to the
          Temporary Expansion Space I is 2000.

     D.   Temporary Expansion Space II From Temporary Expansion Space II
          Expansion Effective Date Through the Temporary Expansion Space
          Termination Date.  For the period commencing with the Temporary
          Expansion Space II Expansion Effective Date and ending on the
          Temporary Expansion Space Termination Date, Tenant shall pay for its
          Pro Rata Share of Expense Excess and Tax Excess applicable to the
          Temporary Expansion Space II in accordance with the terms of the
          Lease, provided, however, during such period, the Base Year for the
          computation of Tenant's Pro Rata Share of Expenses and Taxes
          applicable to the Temporary Expansion Space II is 2000.

VIII.  Improvements to Expansion Spaces.
       --------------------------------

     A.   Condition of Expansion Spaces.  Tenant has inspected the Expansion
          Spaces and agrees to accept the same "as is" without any agreements,
          representations, understandings or obligations on the part of Landlord
          to perform any alterations, repairs or improvements; provided that
          Landlord, at Landlord's cost, will install Building Standard carpet
          (as well as pad and base) in the uncarpeted areas of the Suite 2020
          Expansion Space.

     B.   Cost of Improvements to Expansion Spaces.  Any construction,
          alterations or improvements made to the Expansion Spaces shall be made
          at Tenant's sole cost and expense.

     C.   Responsibility for Improvements to Expansion Spaces.  Except as
          expressly set forth above, any construction, alterations or
          improvements to the Expansion Spaces shall be performed by Tenant
          using contractors selected by Tenant and approved by Landlord and
          shall be governed in all respects by the provisions of Article IX of
          the Lease.  In any and all events, the applicable Expansion Effective
          Date with respect to any such a Expansion Space shall not be postponed
          or delayed if the initial improvements to the Expansion Space are
          incomplete on the applicable Expansion Effective Date for any reason
          whatsoever.  Any delay in the completion of initial improvements to
          the Expansion Spaces shall not subject Landlord to any liability for
          any loss or damage resulting therefrom.

IX.  Early Access to Expansion Space.  During any period that Tenant shall be
     permitted to enter the any of the Expansion Spaces prior to the respective
     Expansion Effective Dates therefore (e.g., to perform alterations or
     improvements), Tenant shall comply with all terms and provisions of the
     Lease, except those provisions requiring payment of Base Rent or Additional
     Rent as to the Expansion Spaces.  If Tenant takes possession of any of the
     Expansion Spaces prior to the applicable Expansion Effective Date therefore
     for any reason whatsoever (other than the performance of work in such
     Expansion Space with Landlord's prior approval), such possession shall be
     subject to all the terms and conditions of the Lease and this Amendment,
     and Tenant shall pay Base

                                       4
<PAGE>

     Rent and Additional Rent as applicable to the Expansion Spaces to Landlord
     on a per diem basis for each day of occupancy prior to the applicable
     Expansion Effective Date.

X.   Renewal Option:  Temporary Expansion Spaces.

     A.   Tenant shall have the right to extend the Term for one or more of the
          Temporary Expansion Spaces (the "Temporary Expansion Space Renewal
          Option") for an additional period commencing on the day following the
          Temporary Expansion Space Termination Date and ending on the Extended
          Termination Date (the "Temporary Expansion Space Renewal Term"), if:

          1.   Landlord receives notice of exercise of the Temporary Expansion
               Space Renewal Option ("Temporary Expansion Space Initial Renewal
               Notice") not less than twelve (12) full calendar months prior to
               Temporary Expansion Space Termination Date and not more than
               fifteen (15) full calendar months prior to the Temporary
               Expansion Space Termination Date (the Initial Temporary Expansion
               Space Renewal Notice must irrevocably specify the Temporary
               Expansion Space(s) which are to be the subject of Tenant's
               exercise of the Temporary Expansion Space Renewal Option); and

          2.   Tenant is not in default under the Lease beyond any applicable
               cure periods at the time that Tenant delivers its Initial
               Temporary Expansion Space Renewal Notice or at the time Tenant
               delivers its Binding Temporary Expansion Space Notice (as
               hereinafter defined); and

          3.   No part of the applicable Temporary Expansion Space is sublet at
               the time that Tenant delivers its Initial Renewal Notice or at
               the time Tenant delivers its Binding Temporary Expansion Space
               Notice, other than in connection with a Permitted Transfer; and

          4.   The Lease has not been assigned prior to the date that Tenant
               delivers its Temporary Expansion Space Initial Renewal Notice or
               prior to the date Tenant delivers its Binding Temporary Expansion
               Space Notice, other than in connection with a Permitted Transfer;
               and

          5.   Tenant executes and returns the Temporary Expansion Space Renewal
               Amendment (hereinafter defined) within fifteen (15) days after
               its submission to Tenant.

     B.   The initial Base Rent rate per rentable square foot for the applicable
          Temporary Expansion Space(s) during the Temporary Expansion Space
          Renewal Term shall equal the Prevailing Market (hereinafter defined)
          rate per rentable square foot for the applicable Temporary Expansion
          Space(s).

     C.   Tenant shall pay Additional Rent for the Premises during the Temporary
          Expansion Space Renewal Term in accordance with Article IV of the
          Lease, as modified by Paragraph VIII above.

     D.   Within thirty (30) days after receipt of Tenant's Initial Renewal
          Notice, Landlord shall advise Tenant of the applicable Base Rent rate
          for the applicable Temporary Expansion Space(s) for the Temporary
          Expansion Space Renewal Term.  Tenant, within fifteen (15) days after
          the date on which Landlord advises Tenant of the applicable Base Rent
          rate for the Temporary Expansion Space Renewal Term, shall either (i)
          give Landlord final binding written notice ("Binding Temporary
          Expansion Space Notice") of Tenant's exercise of its option, or (ii)
          if Tenant disagrees with Landlord's determination, provide Landlord
          with written notice of rejection (the "Rejection Notice").  If Tenant
          fails to provide Landlord with either a Binding Temporary Expansion
          Space Notice or Rejection Notice within such fifteen (15) day period,
          Tenant's Temporary Expansion Space Renewal Option shall be null and
          void and of no further force and effect.  If Tenant provides Landlord
          with a Binding Temporary Expansion Space Notice, Landlord and Tenant
          shall enter into the Temporary Expansion Space Renewal Amendment upon
          the terms and conditions set forth herein.  If Tenant provides
          Landlord with a Rejection Notice, Landlord and Tenant shall work
          together in good faith to agree upon the Prevailing Market Base Rent
          rate for the applicable Temporary Expansion Space(s) during the
          Temporary Expansion Space Renewal Term.  Upon agreement Tenant shall
          provide Landlord with Binding Temporary Expansion Space Notice and
          Landlord and Tenant shall enter into the Temporary Expansion Space
          Renewal Amendment in accordance with the

                                       5
<PAGE>

          terms and conditions hereof. Notwithstanding the foregoing, if
          Landlord and Tenant are unable to agree upon the Prevailing Market
          Base Rent rate for the Premises within thirty (30) days after the date
          on which Tenant provides Landlord with a Rejection Notice, Tenant's
          Renewal Option shall be null and void and of no force and effect.

     E.   If Tenant is entitled to and properly exercises its Temporary
          Expansion Space Renewal Option, Landlord shall prepare an amendment
          (the "Temporary Expansion Space Renewal Amendment") to reflect changes
          in the Base Rent, Term and other appropriate terms.  The Temporary
          Expansion Space Renewal Amendment shall be:

          1.   sent to Tenant within a reasonable time after receipt of the
               Binding Notice; and

          2.   executed by Tenant and returned to Landlord in accordance with
               paragraph A.5 above.

          An otherwise valid exercise of the Temporary Expansion Space Renewal
          Option shall, at Landlord's option, be fully effective whether or not
          the Temporary Expansion Space Renewal Amendment is executed.

     F.   For purpose hereof, "Prevailing Market" shall mean the arms length
          fair market annual rental rate per rentable square foot under renewal
          leases and amendments entered into on or about the date on which the
          Prevailing Market is being determined hereunder for space comparable
          to the applicable Temporary Expansion Space(s) in the Building and
          office buildings comparable to the Building in the Seattle,
          Washington, central business district.  The determination of
          Prevailing Market shall take into account any material economic
          differences between the terms of the Lease and any comparison lease,
          such as rent abatements, construction costs and other concessions and
          the manner, if any, in which the Landlord under any such lease is
          reimbursed for operating expenses and taxes.  The determination of
          Prevailing Market shall also take into consideration any reasonably
          anticipated changes in the Prevailing Market rate from the time such
          Prevailing Market rate is being determined and the time such
          Prevailing Market rate will become effective.

XI.  Other Pertinent Provisions.  Landlord and Tenant agree that, effective as
     of the date hereof (unless different effective date(s) is/are specifically
     referenced in this Section), the Lease shall be amended in the following
     additional respects:

     A.   Exhibit E, Additional Provisions, Item I, Parking, Paragraph A is re-
          written to read as follows:

          "During the Term and Extended Term, Tenant shall have the right to
          receive from Landlord and Landlord agrees to grant to Tenant up to a
          total of 12 unreserved parking permits (the "Permits") in the Building
          garage ("Garage") for the use of Tenant and its employees.  In
          addition, from and after the Expansion Effective Date through the
          Extended Termination Date, Tenant shall have the right to receive from
          Landlord and Landlord agrees to grant to Tenant up to 3 additional
          unreserved Permits in the Garage for the use of Tenant and its
          employees.  Further:

          (i)  from and after the Expansion Effective Date through the Temporary
               Expansion Space Termination Date, Tenant shall have the right to
               receive from Landlord and Landlord agrees to grant to Tenant up 4
               additional unreserved Permits in the Garage for the use of Tenant
               and its employees; and,

          (ii) from and after the Temporary Expansion Space II Expansion
               Effective Date through the Temporary Expansion Space Termination
               Date, Tenant shall have the right to receive from Landlord and
               Landlord agrees to grant to Tenant up to 12 additional unreserved
               Permits in the Garage for the use of Tenant and its employees.

          The number of Permits used by Tenant, up to the maximum specified
          herein, is subject to Tenant's election made from time to time.  No
          deductions or allowances shall be made for days when Tenant or any of
          its employees does not utilize the parking facilities or for Tenant
          utilizing less than all of the Permits.

                                       6
<PAGE>

          Tenant shall not have the right to lease or otherwise use more than
          the number of unreserved Permits set forth above."

XII.  Miscellaneous.
      -------------

     A.   This Amendment sets forth the entire agreement between the parties
          with respect to the matters set forth herein.  There have been no
          additional oral or written representations or agreements.  Under no
          circumstances shall Tenant be entitled to any Rent abatement,
          improvement allowance, leasehold improvements, or other work to the
          Premises, or any similar economic incentives that may have been
          provided Tenant in connection with entering into the Lease, unless
          specifically set forth in this Amendment.

     B.   Except as herein modified or amended, the provisions, conditions and
          terms of the Lease shall remain unchanged and in full force and
          effect.

     C.   In the case of any inconsistency between the provisions of the Lease
          and this Amendment, the provisions of this Amendment shall govern and
          control.

     D.   Submission of this Amendment by Landlord is not an offer to enter into
          this Amendment but rather is a solicitation for such an offer by
          Tenant.  Landlord shall not be bound by this Amendment until Landlord
          has executed and delivered the same to Tenant.

     E.   The capitalized terms used in this Amendment shall have the same
          definitions as set forth in the Lease to the extent that such
          capitalized terms are defined therein and not redefined in this
          Amendment.

     F.   Tenant hereby represents to Landlord that Tenant has dealt with no
          broker in connection with this Amendment other than Clay Nielsen of
          Washington Partners ("Tenant's Broker").  Tenant agrees to indemnify
          and hold Landlord, its members, principals, beneficiaries, partners,
          officers, directors, employees, mortgagee(s) and agents, and the
          respective principals and members of any such agents (collectively,
          the "Landlord Related Parties") harmless from all claims of any
          brokers other than Tenant's Broker claiming to have represented Tenant
          in connection with this Amendment.  Landlord hereby represents to
          Tenant that Landlord has dealt with no broker in connection with this
          Amendment other than Roger Wright of Wright, Runstad Associates
          Limited Partnership ("Landlord's Broker").  Landlord agrees to
          indemnify and hold Tenant, its members, principals, beneficiaries,
          partners, officers, directors, employees, and agents, and the
          respective principals and members of any such agents (collectively,
          the "Tenant Related Parties") harmless from all claims of any brokers,
          other than Landlord's Broker, claiming to have represented Landlord in
          connection with this Amendment.

     G.   This Amendment shall be of no force and effect unless and until
          accepted by any guarantors of the Lease, who by signing below shall
          agree that their guarantee shall apply to the Lease as amended herein,
          unless such requirement is waived by Landlord in writing.

                                       7
<PAGE>

     IN WITNESS WHEREOF, Landlord and Tenant have duly executed this Amendment
as of the day and year first above written.

                            LANDLORD:  EOP-Columbia Center, L.L.C., a Delaware
                                       limited liability company

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties
                                                 Trust, a Maryland real estate
                                                 investment trust, its
                                                 managing general partner


                                            By:
                                               --------------------------------

                                            Name:
                                                 ------------------------------

                                            Title:
                                                  -----------------------------


                            TENANT:  Avenue A, Inc.,
                                     a Washington corporation


                                     By:  /s/ ROBERT M. LITTAUER
                                        ---------------------------------------

                                     Name:  Robert M. Littauer
                                          -------------------------------------

                                     Title:  VP, Chief Financial Officer


                            GUARANTORS (and spouses):

                                                 [Not applicable]
                                     ------------------------------------------

                                       8
<PAGE>

               THIS PAGE IS REQUIRED IF PROPERTY IS IN DELAWARE,
          MICHIGAN, OHIO, UTAH, WASHINGTON, D.C. OR WASHINGTON STATE

                           LANDLORD ACKNOWLEDGMENTS

STATE OF                     )
         --------------------
COUNTY OF                    ) ss:
         --------------------

     I, the undersigned, a Notary Public, in and for the County and State
aforesaid, do hereby certify that ___________________________________________,
personally known to me to be the _________________________________ President of
Equity Office Properties Trust, a Maryland real estate investment trust, and
personally known to me to be the same person whose name is subscribed to the
foregoing instrument, appeared before me this day in person and acknowledged
that as such officer of said entity being authorized so to do, (s)he executed
the foregoing instrument on behalf of said entity, by subscribing the name of
such entity by himself/herself as such officer, as a free and voluntary act, and
as the free and voluntary act and deed of said entity, for the uses and purposes
therein set forth.

     GIVEN under my hand and official seal this ____ day of _____________, 2000.

                                       Notary Public
                                                      -------------------------
                                       Printed Name
                                                     --------------------------

Residing at:
              --------------
My Commission Expires:
                        ------

                             TENANT ACKNOWLEDGMENT
                                  Corporation


STATE OF                     )
         --------------------
COUNTY OF                    ) ss:
         --------------------

     On this the ____ day of _____________________, 2000, before me a Notary
Public duly authorized in and for the said County in the State aforesaid to take
acknowledgments personally appeared __________________________ known to me to be
___________________ President of ________________________, one of the parties
described in the foregoing instrument, and acknowledged that as such officer,
being authorized so to do, (s)he executed the foregoing instrument on behalf of
said corporation by subscribing the name  of such corporation by himself/herself
as such officer and caused the corporate seal of said corporation to be affixed
thereto, as a free and voluntary act, and as the free and voluntary act of said
corporation, for the uses and purposes therein set forth.

     IN WITNESS WHEREOF, I hereunto set my hand and official seal.

                                       Notary Public /s/ TAMARA J. VAN LIEW
                                                     --------------------------
                                       Printed Name  TAMARA J. VAN LIEW
                                                     --------------------------

Residing at: Avenue A. Inc.
            ----------------------
My Commission Expires: 7-1-03
                      ------------

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                                   EXHIBIT A

                                   Floor Plan

                       Showing Suite 2020 Expansion Space

                                       1
<PAGE>

                                   EXHIBIT A

                                   Floor Plan

                       Showing Suite 2054 Expansion Space

                                       1
<PAGE>

                                   EXHIBIT A

                                   Floor Plan

                       Showing Suite 2510 Expansion Space

                                       1
<PAGE>

                                   EXHIBIT A

                                   Floor Plan

                      Showing Temporary Expansion Space II
                                  (Suite 1400)

                                       2