Document:

<PAGE>

                                                                   EXHIBIT 10.10

                        FOURTH AMENDMENT TO OFFICE LEASE

         THIS FOURTH AMENDMENT TO OFFICE LEASE (this "Amendment") is made and
entered into as of July 15, 2001, by and between 100 PINE STREET, L.P., a
Delaware limited partnership ("Landlord"), and ART TECHNOLOGY GROUP, INC., a
Delaware corporation ("Tenant").

                                    RECITALS

         A.       Landlord, as successor-in-interest to Pine Street Investors I,
L.L.C., a Delaware limited liability company, and Tenant have entered into that
certain Office Lease dated as of October 6, 1999 (the "Original Lease"), as
amended by that certain First Amendment to Lease (the "First Amendment") dated
as of December 30, 1999, that certain Second Amendment to Office Lease (the
"Second Amendment") dated as of August 28, 2000, and that certain Third
Amendment to Office Lease (the "Third Amendment") dated as of December 22, 2000
(as so amended, the "Lease"). Unless otherwise defined herein, capitalized terms
used in this Amendment shall have the meanings given to such terms in the Lease.

         B.       Pursuant to the Original Lease, Landlord leased to Tenant the
entire 21st floor of that certain office building located at 100 Pine Street,
San Francisco, California (the "Building").

         C.       Pursuant to the Second Amendment, Landlord agreed to lease
Tenant approximately 9,947 rentable square feet on the 20th floor of the
Building and the entire 25th floor of the Building (as more particularly
described in the Second Amendment, the "25th Floor Space").

         D.       Pursuant to the Third Amendment, Landlord agreed to lease
Tenant an additional approximately 3,263 rentable square feet on the 20th floor
of the Building, which constitutes Suite 2040 of the Building.

         E.       The Target Delivery Date of the 25th Floor Space was June 15,
2001.

         F.       Tenant desires to terminate its rights and obligations under
the Lease with respect to the 25th Floor Space. Landlord has agreed to such
termination upon the satisfaction of the terms and conditions set forth herein.

         NOW, THEREFORE, the parties hereto agree as follows:

         1.       Landlord anticipates delivery of possession of the 25th Floor
Space to Tenant on July 1, 2001.

         2.       Tenant's rights and obligations under the Lease with respect
to the 25th Floor Space shall terminate as of the date that all of the following
conditions have been satisfied (which date is referred to herein as the
"Effective Date"):

                  (a)      Landlord has entered into a lease amendment with
MWBH&L Leasing Corp., a California corporation ("Milberg"), in form and
substance satisfactory to Landlord in its sole and absolute discretion, pursuant
to which Milberg leases the entire 25th Floor Space from

<PAGE>

Landlord, with a term commencing on or about November 1, 2001 and expiring
December 31, 2011 (the "Milberg Amendment").

                  (b)      Landlord has received from Milberg an additional
unconditional, irrevocable standby letter of credit in the amount of One Million
Dollars ($1,000,000) in favor Landlord, in a form satisfactory to Landlord, as
security for Milberg's performance of its obligations with respect to the 25th
Floor Space under the Milberg Amendment.

                  (c)      Concurrently with the execution of this Amendment,
Tenant has paid to Landlord same day funds in an amount equal to the net present
value of the difference between the Base Rent payable under the Lease for the
25th Floor Space and the base rent payable by Milberg under the Milberg
Amendment for the 25th Floor Space, calculated as of the date Landlord executes
this Amendment, as evidenced by the date adjacent Landlord's signature to this
Amendment (the "Landlord's Execution Date") (such amount shall be referred to
herein as the "Early Termination Fee"). Attached as Exhibit A hereto, is a
calculation of the amount of the Early Termination Fee if Landlord's Execution
Date were July 15, 2001, which fee would be $1,831,402.00 in accordance with
such calculation. In the event that Landlord's Execution Date is either before
or after July 15, 2001, the Early Termination Fee shall be calculated as of that
date, in accordance with the formula used in the sample calculation set forth in
Exhibit A.

                  (d)      On or before the Effective Date, Tenant shall have
surrendered possession of the 25th Floor Space in the same condition it was in
on July 1, 2001.

         3.       Upon the satisfaction of the conditions set forth in Paragraph
2, Tenant shall have no further rights, including without limitation, the right
to use and occupancy, or obligations, including without limitation, the
obligation to pay Rent under the Lease with respect to the 25th Floor Space,
except pursuant to any provisions of the Lease which expressly survive the
expiration or termination of the Lease.

         4.       If any of the conditions precedent listed in Paragraph 2
above, are not satisfied by August 15, 2001 (the "Determination Date"), (i)
Tenant's rights and obligations under the Lease with respect to the 25th Floor
Space shall not terminate and shall continue in full force and effect and (ii)
the provisions of this Amendment shall be void and of no further force or
effect, except for the applicable provisions of this Paragraph and Paragraphs 5,
6, 12, 13, and 14 below. In the event that the conditions precedent listed in
Paragraph 2 above, are not satisfied by the Determination Date, but Tenant has
paid Landlord the Early Termination Fee, Landlord shall refund Tenant the Early
Termination Fee, together with any interest accrued thereon between the Landlord
Execution Date and the date on which Landlord refunds Tenant the Early
Termination Fee.

         5.       The parties agree that notwithstanding anything to the
contrary contained in the Lease and Landlord's delivery of the 25th Floor Space
as of July 1, 2001, Tenant shall not be required to pay the first month's Base
Rent for the 25th Floor Space, upon such delivery of the 25th Floor Space.
However, in the event that Tenant's rights and obligations under the Lease with
respect to the 25th Floor Space are not terminated, Tenant shall pay any Base
Rent that otherwise would have been payable pursuant to the terms of the Lease,
within five (5) days following the Determination Date.

                                       2

<PAGE>

         6.       Tenant acknowledges that notwithstanding anything to the
contrary set forth in the Lease, Landlord shall have no obligation to pay to
Tenant the 25th Floor Allowance or perform Landlord's Work (as such terms are
defined in the Second Amendment) in the event that the Lease with respect to the
25th Floor Space is terminated pursuant to the terms of this Amendment. However,
in the event that Tenant's rights and obligations under the Lease with respect
to the 25th Floor Space are not terminated by the Determination Date, and Tenant
provides Landlord written notice of its intention to make any repairs,
refurbishments, improvements, or alterations to the 25th Floor Space, as
contemplated by Section 2(f) of the Second Amendment (the "Tenant's Work"),
Landlord shall pay Tenant the 25th Floor Allowance in accordance with the terms
of the Second Amendment as Tenant performs Tenant's Work.

         7.       As of the Effective Date, Tenant may amend the Letter of
Credit provided for in the Second Amendment (the "Second LOC"), to reduce the
amount thereof from $2,215,863.90 to $1,500,000, provided that (i) the form and
substance of any amendment is acceptable to Landlord and to the beneficiary of
any deed of trust encumbering the Property and (ii) the Tenant shall pay all
expenses, points or fees associated with any such amendment of the Second LOC.
In lieu of amending the Second LOC, Tenant may provide Landlord a replacement
letter of credit in the amount of $1,500,000, which replacement letter of credit
shall conform with all the requirements set forth herein and in Paragraph 4 of
the Second Amendment. In the event that Tenant delivers Landlord a replacement
letter of credit in accordance with the terms of this Paragraph 7, Landlord
shall surrender the existing Second LOC to Tenant. The Second LOC, as it may be
amended or replaced pursuant to the terms of this Paragraph 7, shall be held by
Landlord as security for the performance of Tenant's obligations under the Lease
and shall conform with and be used or applied as set forth in Paragraph 4 of the
Second Amendment and the Original Lease.

         8.       The 14th sentence of Paragraph 4 of the Second Amendment is
deleted as of the Effective Date and replaced with the following: "If Landlord
uses or applies any portion of the Letter of Credit, Tenant shall, within ten
(10) business days after demand (a) deposit cash (which shall constitute an
additional Security Deposit) with Landlord in an amount that, when added to the
amount remaining under the Letter of Credit, equals $1,500,000, or (b) deliver
written documentation executed by the bank issuing the Letter of Credit that
confirms that the Letter of Credit has been reinstated or a new or additional
Letter of Credit issued in such full amount, and Tenant's failure to do so shall
constitute a material breach of the Lease."

         9.       As of the Effective Date, the last sentence of Paragraph 4 of
the Second Amendment is hereby deleted in its entirety.

         10.      Nothing contained in this Amendment shall in anyway modify the
terms or conditions of the Letters of Credit delivered to Landlord by Tenant
pursuant to the First and Third Amendments.

         11.      The provisions of Paragraphs 7, 8 and 9 above will be void and
of no force or effect if the conditions set forth in Paragraph 2 above are not
satisfied by the Determination Date.

                                       3

<PAGE>

         12.      The parties warrant and represent that they have had no
dealings with any real estate brokers or agents in connection with the
negotiation of this Amendment, except for CAC Group, Insignia/ESG, Inc., Trammel
Crow Company, and The Irving Hughes Group, and that they know of no real estate
broker or agent who is or might be entitled to a commission or finder's fee in
connection with this Amendment. The parties agree to defend, indemnify and hold
each other and each other's agents, employees, officers and directors harmless
from and against any and all liabilities or expenses, including reasonable
attorneys' fees and costs, arising out of or in connection with the claims made
by any broker or individual for commissions or fees resulting from the parties'
execution of this Amendment. Landlord shall pay the fees of the CAC Group and
Tenant shall pay the fees of Insignia/ESG, Inc., Trammel Crow Company, and The
Inning Hughes Group.

         13.      The parties agree that they shall each pay their own
attorneys' fees and costs incurred in connection with this Amendment.

         14.      Except as modified by this Amendment, all of the terms and
provisions of the Lease shall remain in full force and effect and are hereby
ratified and confirmed by the parties.

         15.      This Amendment may be executed in two or more counterparts,
each of which shall be deemed to be an original, but all of which, taken
together, shall constitute one and the same instrument.

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the day and year first above written.

LANDLORD:                                  100 PINE STREET, L.P.,
                                           a Delaware limited partnership

Dated: July 15, 2001                       By: UNICO Properties, Inc.,
                                               a Delaware corporation,
                                               its Managing Agent

                                           By: /s/ Jeffrey R. Shipley
                                               -------------------------
                                               Jeffrey R. Shipley,
                                               Senior Vice President

TENANT:                                    ART TECHNOLOGY GROUP, INC.,
                                           a Delaware corporation

                                           By: /s/ Paul G. Shorthose
                                               -------------------------
                                           Name: Paul G. Shorthose
                                           Its:  President
                                               -------------------------

                                       4

<PAGE>

                                    EXHIBIT A

                                  See Attached

                                       5

<PAGE>

                                    Exhibit A

                   NPV of Art Technology Lease Buyout @ 10.50%

   Monthly Discounting to 11/1/01

<TABLE>
<S>                      <C>
Yearly Discount Rate          10.50%
Monthly Discount Rate         0.675%
-----------------------------------
NPV                      $1,707,021
------------------------------------
Rent                     $       20
SF                           13,692
$/YR                     $  273,840
$/MO                     $   22,820
-----------------------------------
Last Payment               12/01/11
</TABLE>

   Daily discounting to 1/15/01

<TABLE>
<S>                    <C>
Year Discount Rate          10.50%
Daily Discount Rate         0.029%
---------------------------------
NPV                    $1,831,402
---------------------------------
Rent                   $       95
SF                         13,692
$/YR                   $1,300,740
$/MO                   $  108,395
---------------------------------
</TABLE>

<TABLE>
<CAPTION>
-------  ------------
  Date    Cash Flow
-------  ------------
<S>      <C>
11/1/01   $22,820.00
12/1/01   $22,820.00
 1/1/02   $22,820.00
 2/1/02   $22,820.00
 3/1/02   $22,820.00
 4/1/02   $22,820.00
 5/1/02   $22,820.00
 6/1/02   $22,820.00
 7/1/02   $22,820.00
 8/1/02   $22,820.00
 9/1/02   $22,820.00
10/1/02   $22,820.00
11/1/02   $22,820.00
12/1/02   $22,820.00
 1/1/03   $22,820.00
 2/1/03   $22,820.00
 3/1/03   $22,820.00
 4/1/03   $22,820.00
 5/1/03   $22,820.00
 6/1/03   $22,820.00
 7/1/03   $22,820.00
 8/1/03   $22,820.00
 9/1/03   $22,820.00
10/1/03   $22,820.00
11/1/03   $22,820.00
12/1/03   $22,820.00
 1/1/04   $22,820.00
 2/1/04   $22,820.00
 3/1/04   $22,820.00
 4/1/04   $22,820.00
 5/1/04   $22,820.00
 6/1/04   $22,820.00
 7/1/04   $22,820.00
 8/1/04   $22,820.00
 9/1/04   $22,820.00
10/1/04   $22,820.00
11/1/04   $22,820.00
12/1/04   $22,820.00
 1/1/05   $22,820.00
 2/1/05   $22,820.00
 3/1/05   $22,820.00
 4/1/05   $22,820.00
 5/1/05   $22,820.00
 6/1/05   $22,820.00
 7/1/05   $22,820.00
 8/1/05   $22,820.00
 9/1/05   $22,820.00
10/1/05   $22,820.00
11/1/05   $22,820.00
12/1/05   $22,820.00
 1/1/06   $22,820.00
 2/1/06   $22,820.00
 3/1/06   $22,820.00
 4/1/06   $22,820.00
7/15/01   $        0
7/16/01   $        0
7/17/01   $        0
7/18/01   $        0
7/19/01   $        0
7/20/01   $        0
7/21/01   $        0
7/22/01   $        0
7/23/01   $        0
7/24/01   $        0
7/25/01   $        0
7/26/01   $        0
7/27/01   $        0
7/28/01   $        0
7/29/01   $        0
7/30/01   $        0
7/31/01   $        0
 8/1/01   $        0
 8/2/01   $        0
 8/3/01   $        0
 8/4/01   $        0
 8/5/01   $        0
 8/6/01   $        0
 8/7/01   $        0
 8/8/01   $        0
 8/9/01   $        0
8/10/01   $        0
8/11/01   $        0
8/12/01   $        0
8/13/01   $        0
8/14/01   $        0
8/15/01   $        0
8/16/01   $        0
8/17/01   $        0
8/18/01   $        0
8/19/01   $        0
8/20/01   $        0
8/21/01   $        0
8/22/01   $        0
8/23/01   $        0
8/24/01   $        0
8/25/01   $        0
8/26/01   $        0
8/27/01   $        0
8/28/01   $        0
8/29/01   $        0
8/30/01   $        0
8/31/01   $        0
 9/1/01   $        0
 9/2/01   $        0
 9/3/01   $        0
 9/4/01   $        0
 9/5/01   $        0
 9/6/01   $        0
</TABLE>

                                       6

<PAGE>

<TABLE>
<S>       <C>
 5/1/06   $22,820.00
 6/1/06   $22,820.00
 7/1/06   $22,820.00
 8/1/06   $22,820.00
 9/1/06   $22,820.00
10/1/06   $22,820.00
11/1/06   $22,820.00
12/1/06   $22,820.00
 1/1/07   $22,820.00
 2/1/07   $22,820.00
 3/1/07   $22,820.00
 4/1/07   $22,820.00
 5/1/07   $22,820.00
 6/1/07   $22,820.00
 7/1/07   $22,820.00
 8/1/07   $22,820.00
 9/1/07   $22,820.00
10/1/07   $22,820.00
11/1/07   $22,820.00
12/1/07   $22,820.00
 1/1/08   $22,820.00
 2/1/08   $22,820.00
 3/1/08   $22,820.00
 4/1/08   $22,820.00
 5/1/08   $22,820.00
 6/1/08   $22,820.00
 7/1/08   $22,820.00
 8/1/08   $22,820.00
 9/1/08   $22,820.00
10/1/08   $22,820.00
11/1/08   $22,820.00
12/1/08   $22,820.00
 1/1/09   $22,820.00
 2/1/09   $22,820.00
 3/1/09   $22,820.00
 4/1/09   $22,820.00
 5/1/09   $22,820.00
 6/1/09   $22,820.00
 7/1/09   $22,820.00
 8/1/09   $22,820.00
 9/1/09   $22,820.00
10/1/09   $22,820.00
11/1/09   $22,820.00
12/1/09   $22,820.00
 1/1/10   $22,820.00
 2/1/10   $22,820.00
 3/1/10   $22,820.00
 4/1/10   $22,820.00
 5/1/10   $22,820.00
 6/1/10   $22,820.00
 7/1/10   $22,820.00
 8/1/10   $22,820.00
10/1/10   $22,820.00
11/1/10   $22,820.00
12/1/10   $22,820.00
 1/1/11   $22,820.00
 2/1/11   $22,820.00
 3/1/11   $22,820.00
 4/1/11   $22,820.00
 5/1/11   $22,820.00
 6/1/11   $22,820.00
 7/1/11   $22,820.00
 8/1/11   $22,820.00
 9/1/11   $22,820.00
10/1/11   $22,820.00
11/1/11   $22,820.00
12/1/11   $22,820.00
 9/7/01   $        0
 9/8/01   $        0
 9/9/01   $        0
9/10/01   $        0
9/11/01   $        0
9/12/01   $        0
9/13/01   $        0
9/14/01   $        0
9/15/01   $   57,811
9/16/01   $        0
9/17/01   $        0
9/18/01   $        0
9/19/01   $        0
9/20/01   $        0
9/21/01   $        0
9/22/01   $        0                    This cash flow equals the present value
9/23/01   $        0                    of the monthly rent payments between
9/24/01   $        0                    11/1/01 - 12/31/01 added to current
9/25/01   $        0                    rent payment due on 10/1/01.
9/26/01   $        0
9/27/01   $        0
9/28/01   $        0
9/29/01   $        0
9/30/01   $        0
10/1/01   $1,815,416
</TABLE>

                                       7<PAGE>

                                                                   Exhibit 10.11

                         FIFTH AMENDMENT TO OFFICE LEASE

         THIS FIFTH AMENDMENT TO OFFICE LEASE (this "FIFTH AMENDMENT") is made
and entered into as of March 31, 2003, by and between 100 PINE STREET, L.P., a
Delaware limited partnership ("LANDLORD"), and ART TECHNOLOGY GROUP, INC., a
Delaware corporation ("TENANT").

                                    RECITALS

         A.       Landlord, as successor-in-interest to Pine Street Investors I,
L.L.C., a Delaware limited liability company, and Tenant have entered into that
certain Office Lease dated as of October 6, 1999 (the "ORIGINAL LEASE"), as
amended by that certain First Amendment to Lease (the "FIRST AMENDMENT") dated
as of December 30, 1999, that certain Second Amendment to Office Lease (the
"SECOND AMENDMENT") dated as of August 28, 2000, that certain Third Amendment to
Office Lease (the "THIRD AMENDMENT") dated as of December 22, 2000, and that
certain Fourth Amendment to Office Lease (the "FOURTH AMENDMENT") dated as of
July 15, 2001 (as so amended, the "LEASE"). Unless otherwise defined herein,
capitalized terms used in this Fifth Amendment shall have the meanings given to
such terms in the Lease.

         B.       Pursuant to the Original Lease, Landlord leased to Tenant the
entire 21st floor of that certain office building located at 100 Pine Street,
San Francisco, California (the "BUILDING").

         C.       Pursuant to the Second Amendment, Landlord agreed to lease
Tenant approximately 9,947 rentable square feet on the 20th floor of the
Building and the entire 25th floor of the Building (as more particularly
described in the Second Amendment, the "25TH FLOOR SPACE").

         D.       Pursuant to the Third Amendment, Landlord agreed to lease
Tenant an additional approximately 3,263 rentable square feet on the 20th floor
of the Building (all of Tenant's leased space on the 20th Floor, collectively,
the "20TH FLOOR SPACE"; the 25th Floor Space and the 20th Floor Space,
collectively, the "EXPANSION SPACE").

         E.       Pursuant to the Fourth Amendment, provision was made, in
addition to certain other modifications, for a conditional termination of the
25th Floor Space, however, the pre-conditions to such termination were never
satisfied.

         F.       Tenant now desires to terminate its rights and obligations
under the Lease with respect to the Expansion Space. Landlord has agreed to such
termination upon the satisfaction of the terms and conditions set forth herein.

         NOW, THEREFORE, the parties hereto agree as follows:

         1.       EFFECTIVENESS; CONDITIONS PRECEDENT. Upon execution by each of
Landlord and Tenant the agreement to amend contained in this Fifth Amendment
shall be fully binding on Landlord and Tenant as of the date hereof.
Notwithstanding the foregoing, the specific amendments contained in Section 2
though Section 7 and the mutual releases set forth in Section 11 shall not take
effect until the first day of the first calendar month immediately

<PAGE>

following satisfaction, to Landlord's reasonable satisfaction, of each of the
conditions listed below (the "EFFECTIVE DATE"):

                  (a)      Tenant shall have paid to Landlord as compensation
for the Landlord's agreement to accept and early termination of the Lease with
respect to the Expansion Space and to consent to the lease modifications
contained herein, immediately available funds in an amount equal to $6,750,000;

                  (b)      Tenant shall have paid to Landlord as reimbursement
to Landlord of its costs, expenses and legal fees incurred in negotiating and
documenting this Fifth Amendment, immediately available funds in an amount not
to exceed $15,000;

                  (c)      Tenant shall have surrendered possession of the
Expansion Space in broom clean condition; and

                  (d)      Not later than April 15, 2003, Tenant and Landlord
shall have executed, and Landlord's lender shall have consented to, this Fifth
Amendment.

Landlord and Tenant acknowledge and agree that in the event all of the
conditions set forth above have not been satisfied on or before April 15, 2003,
this Fifth Amendment shall automatically be deemed terminated and shall be null
and void and of no further force or effect, whereupon the parties shall be
released from all obligations hereunder, except for the brokerage indemnity set
forth in Section 8 below which shall expressly survive such termination.

         2.       TERMINATION OF EXPANSION SPACE. Upon the satisfaction of the
conditions set forth in Section 1 above, Tenant shall have no further rights,
including without limitation, the right to use and occupancy, or obligations,
including without limitation, the obligation to pay Rent under the Lease with
respect to the Expansion Space, except (a) pursuant to any provisions of the
Lease which expressly survive the expiration or termination of the Lease or (b)
with respect to additional Rent (as set out in Section 4 of the Lease) with
respect to the Expansion Space which accrues prior to the Effective Date, but
which is, in the ordinary course, to be billed to Tenant after the Effective
Date (which additional Rent Tenant shall pay to Landlord when due in accordance
with the Lease).

         3.       REDUCTION OF BASE RENT. Commencing on the Effective Date but
retroactive to the date this Fifth Amendment was last signed (as reflected by
the dates on the signature page hereto), and for the remainder of the Lease term
thereafter (as such Lease term has been extended by this Fifth Amendment), the
Base Rent for the Premises remaining encumbered by the Lease (i.e. the 21st
Floor) shall be reduced to $35 per rentable square foot per year. The Premises,
following the Effective Date, shall consist of 12,931 rentable square feet with
an annual Base Rent of $452,585 and a monthly Base Rent of $37,715.42, all due
in accordance with the provisions of the Lease.

         4.       TENANT'S PRORATA SHARE. As of the Effective Date and
termination of the Lease with respect to the Expansion Space, Tenant's Prorata
Share shall be 3.212 %, and Tenant's Prorata Share of Operating Expenses and
Taxes shall continue to be paid pursuant to the terms of the Lease.

                                     Page 2

<PAGE>

         5.       FORFEITURE OF TI ALLOWANCE. Tenant acknowledges agrees that
(a) any and all rights Tenant has under the lease to receive a tenant
improvement allowance from Landlord are hereby forfeited, cancelled and
terminated, whether or not such rights may have accrued prior to the Effective
Date and (b) as a result of such forfeiture, termination and cancellation,
Landlord has no further obligation under the Lease to provide any tenant
improvement allowance to Tenant at any time.

         6.       LETTERS OF CREDIT AND SECURITY DEPOSIT.

                  (a)      Tenant acknowledges that Landlord is currently
holding a security deposit (the "SECURITY DEPOSIT") in the amount of
$158,404.75. The parties hereby agree that Landlord shall continue to hold the
Security Deposit until the expiration of the Lease Term, and in no event shall
the amount of the Security Deposit be reduced except in accordance with the
provisions of the Lease.

                  (b)      Tenant further acknowledges that Landlord is
currently holding three (3) letters of credit (the "LETTERS OF CREDIT") to
guaranty Tenant's obligations under the Lease, in an aggregate amount of
$2,285,098. Notwithstanding any Lease provisions to the contrary, the parties
hereby agree that Tenant shall have the right to reduce the amount of the
Letters of Credit held by Landlord on the following schedule, provided that
there has not occurred any Default under the Lease at any time following the
Effective Date and that all costs and expenses associated with any such
reduction shall be entirely borne by Tenant:

<TABLE>
<CAPTION>
DATE OF ALLOWED REDUCTION         REQUIRED LETTERS OF CREDIT
-------------------------         --------------------------
<S>                               <C>
     November 30, 2004                  $1,832,513
     November 30, 2005                  $1,379,928
     November 30, 2006                  $  927,343
     November 30, 2007                  $  474,758
</TABLE>

         If Tenant, pursuant to this Section 6, at any time desires to reduce
the aggregate amount of the Letters of Credit held by Landlord, Tenant shall
provide Landlord with written notice thereof and Landlord shall then cooperate
with Tenant in a timely manner to effectuate such reduction (which Tenant
acknowledges will take some coordination with Landlord's lender and the issuing
bank(s) of the Letters of Credit). Any reduction in the Letters of Credit shall
be achieved by a cancellation and/or partial reduction in the amount of one or
more Letters of Credit (with the order of cancellation or reduction of the three
existing Letters of Credit to be determined by Landlord in its sole discretion).

         7.       EXTENSION OF EXPIRATION DATE; EXTENSION OPTION. The Expiration
Date under the Lease is hereby amended to be December 31, 2007. Due to the
cancellation of the Expansion Space, the Tenant acknowledges that the Option to
Extend the Term of the Lease set forth in Rider 2 to the Lease shall only apply
with respect to the Premises which remain encumbered by the Lease after the
Effective Date.

         8.       BROKERS. Landlord and Tenant hereby warrant to each other that
they have had no dealings with any real estate broker or agent in connection
with the negotiation of this Fifth Amendment, and that they know of no real
estate broker or agent who is entitled to a commission

                                     Page 3

<PAGE>

in connection with this Fifth Amendment. Each party agrees to indemnify and
defend the other party against and hold the other party harmless from any and
all claims, demands, losses, liabilities, lawsuits, judgments, and costs and
expenses (including, without limitation, reasonable attorneys' fees) with
respect to any leasing commission or equivalent compensation alleged to be owing
on account of the indemnifying party's dealings with any real estate broker or
agent. The terms of this Section 8 shall survive the expiration or earlier
termination of this Fifth Amendment.

         9.       INCORPORATION; NO FURTHER MODIFICATION. From and after the
effective date hereof, the term "Lease" as used in the Lease shall mean the
Lease, as amended by the First, Second, Third, Fourth and Fifth Amendments.
Except as set forth in this Fifth Amendment, all of the terms and provisions of
the Lease shall apply with respect to the Premises and shall remain unmodified
and in full force and effect and are hereby ratified and confirmed.

         10.      COUNTERPARTS. This Fifth Agreement may be executed in one or
more counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument. The parties agree that
the signature page to this Fifth Agreement may be executed and delivered by
facsimile transmission and that such execution and delivery shall be deemed
effective for all purposes hereunder.

         11.      MUTUAL RELEASE.

         (a)      Except as noted in Section 2 hereof, Landlord hereby (i) fully
and irrevocably releases and forever discharges Tenant and Tenant's employees,
successors and assigns, from any and all claims, counterclaims, causes of
action, suits, debts, controversies, damages, judgments, executions, claims,
demands and liabilities, of whatever kind and nature, fixed or contingent, known
or unknown, arising at law or in equity, which they ever had, now have or
hereafter can, shall or may have for, upon or by reason of any matters, cause or
thing whatsoever from the beginning of time to and including the date hereof
relating to or in any way arising from or in connection with the Expansion
Space; and (ii) covenants and agrees not to sue, prosecute or cause to be
commenced or prosecuted any suit, activity, claim or other procedure based on
the foregoing. For purposes of clarification, the parties agree that Landlord
does not and has not released Tenant from those indemnity obligations under the
Lease which expressly survive Lease termination or from Tenant's obligations to
pay additional Rent which accrue prior to the Effective Date with respect to the
Expansion Space.

         (b)      Tenant hereby (i) fully and irrevocably releases and forever
discharges Landlord and Landlord's employees, successors and assigns, from any
and all claims, counterclaims, causes of action, suits, debts, controversies,
damages, judgments, executions, claims, demands and liabilities, of whatever
kind and nature, fixed or contingent, known or unknown, arising at law or in
equity, which they ever had, now have or hereafter can, shall or may have for,
upon or by reason of any matters, cause or thing whatsoever from the beginning
of time to and including the date hereof relating to or in any way arising from
or in connection with the Expansion Space; and (ii) covenants and agrees not to
sue, prosecute or cause to be commenced or prosecuted any suit, activity, claim
or other procedure based on the foregoing.

                  (REMAINDER OF PAGE INTENTIONALLY LEFT BLANK)

                                     Page 4

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this Fifth
Amendment as of the day and year first above written.

              [PROVIDE A DATE OF EXECUTION NEXT TO EACH SIGNATURE]

LANDLORD:        100 PINE STREET, L.P., a Delaware limited partnership

                 By:  UNICO Properties, Inc., a Delaware corporation,
                      its Managing Agent

                      By: /s/ John D. Lamb                            5/7/2003
                          --------------------------------------      ----------
                          John D. Lamb, Senior Vice President         Date

TENANT:          ART TECHNOLOGY GROUP, INC.,
                 a Delaware corporation

                      By:   /s/ Edward Terino                         5/7/2003
                          --------------------------------------      ----------
                      Name: Edward Terino                               Date
                          --------------------------------------
                      Its:  Chief Financial Officer
                          --------------------------------------

         CONSENTED TO BY:

         GERMAN AMERICAN CAPITAL CORPORATION,
         a Maryland corporation

         By:
                --------------------------------------      ----------
         Name:                                                 Date
                --------------------------------------
         Title:
                --------------------------------------

         By:
                --------------------------------------      ----------
         Name:                                                 Date
                --------------------------------------
         Title:
                --------------------------------------

                                     Page 5

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