Document:

<PAGE>
                                                                    EXHIBIT 10.2
                     2006 NON-EMPLOYEE DIRECTOR COMPENSATION

      For their service to Idenix in 2006, effective as of 2006 annual meeting
of stockholders, non-employee directors will receive the following compensation:

<TABLE>
<CAPTION>
                                                                               OPTIONS TO PURCHASE
                                                                                 COMMON STOCK(1)
                                                          MEETING FEES     ----------------------------
                                                          (PER MEETING
                                         CASH RETAINER     ATTENDED)         INITIAL         ANNUAL
                                         --------------   ------------     ----------     -------------
<S>                                      <C>              <C>              <C>            <C>
Board Member                               $     30,000   $      2,000         15,000(2)         20,000(3)

Committee Chair (other than Audit)                5,000          1,000             --                --

Audit Committee Chair                             8,000          1,000             --                --

Committee Members (other than chair)                 --          1,000

</TABLE>

(1)   The exercise price of these options is equal to the fair market value of
      our common stock on the date of grant as reported by NASDAQ. Each option
      terminates on the earlier of ten years from the date of grant or 180 days
      after the optionee ceases to serve as a director, except in the case of
      death or disability, in which event the option terminates one year from
      the date of the director's death or disability.

(2)   Each non-employee director is entitled to receive an award of stock
      options upon his or her election or appointment to our board of directors.
      In 2006, the vesting period for any options awarded upon initial
      appointment will vest in 24 equal monthly installments from the date of
      grant.

(3)   Each non-employee director is entitled to receive at each year's annual
      meeting after which he or she continues to serve as a director, an
      additional option grant of 20,000 shares. The number of options to be
      awarded to new non-employee directors who are appointed to our board of
      directors at times other than immediately after the annual meeting of
      stockholders will be prorated for the period of service between date of
      appointment and the next annual meeting. The annual option grant vests in
      12 equal monthly installments from the date of grant.

      In addition, members of our board of directors, other than directors
      affiliated with Novartis, are reimbursed for expenses incurred in
      connection with attendance at meetings of our board of directors and its
      committees and related activities in accordance with Idenix policy.<PAGE>

                                                                   EXHIBIT 10.33

                                      LEASE

                        RREEF AMERICA REIT II CORP. PPP,

                                    Landlord,

                                       and

                           ART TECHNOLOGY GROUP, INC.,

                                     Tenant

                             Riverfront Office Park
                            Cambridge, Massachusetts

<PAGE>

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
<S>                                                                         <C>
1.   USE AND RESTRICTIONS ON USE.........................................     1
2.   TERM................................................................     2
3.   RENT................................................................     3
4.   RENT ADJUSTMENTS....................................................     3
5.   SECURITY DEPOSIT....................................................     5
6.   ALTERATIONS.........................................................     7
7.   REPAIR..............................................................     8
8.   LIENS...............................................................     8
9.   ASSIGNMENT AND SUBLETTING...........................................     8
10.  INDEMNIFICATION.....................................................    10
11.  INSURANCE...........................................................    10
12.  WAIVER OF SUBROGATION...............................................    11
13.  SERVICES AND UTILITIES..............................................    11
14.  HOLDING OVER........................................................    13
15.  SUBORDINATION.......................................................    13
16.  RULES AND REGULATIONS...............................................    13
17.  REENTRY BY LANDLORD.................................................    13
18.  DEFAULT.............................................................    14
19.  REMEDIES............................................................    15
20.  TENANT'S BANKRUPTCY OR INSOLVENCY...................................    17
21.  QUIET ENJOYMENT.....................................................    18
22.  CASUALTY............................................................    18
23.  EMINENT DOMAIN......................................................    19
24.  SALE BY LANDLORD....................................................    19
25.  ESTOPPEL CERTIFICATES...............................................    20
26.  SURRENDER OF PREMISES...............................................    20
27.  NOTICES.............................................................    20
28.  TAXES PAYABLE BY TENANT.............................................    21
29.  INTENTIONALLY DELETED...............................................    21
30.  DEFINED TERMS AND HEADINGS..........................................    21
31.  TENANT'S AUTHORITY..................................................    21
32.  FINANCIAL STATEMENTS AND CREDIT REPORTS.............................    22
33.  COMMISSIONS.........................................................    22
34.  TIME AND APPLICABLE LAW.............................................    22
35.  SUCCESSORS AND ASSIGNS..............................................    22
</TABLE>

                                       -i-

<PAGE>

                                TABLE OF CONTENTS
                                  (continued)

<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
<S>                                                                         <C>
36.  ENTIRE AGREEMENT....................................................    22
37.  EXAMINATION NOT OPTION..............................................    22
38.  RECORDATION.........................................................    22
39.  PARKING.............................................................    22
40.  RENEWAL OPTION......................................................    24
41.  RIGHT OF FIRST OFFER................................................    24
42.  EXPANSION OPTION....................................................    25
43.  LIMITATION OF LANDLORD'S LIABILITY..................................    26

EXHIBIT A - FLOOR PLAN DEPICTING THE PREMISES............................     1
EXHIBIT A-1 - SITE PLAN..................................................     1
EXHIBIT A-2 - LEGAL DESCRIPTION OF THE LOT...............................     1
EXHIBIT B - INITIAL ALTERATIONS..........................................     1
EXHIBIT C - COMMENCEMENT DATE MEMORANDUM.................................     1
EXHIBIT D - RULES AND REGULATIONS........................................     1
EXHIBIT E - ELECTRICITY COSTS............................................     1
EXHIBIT F - EXPANSION PREMISES...........................................     1
</TABLE>

                                      -ii-

<PAGE>

                           GROSS (BY)-INS OFFICE LEASE

                                 REFERENCE PAGES

<TABLE>
<S>                                     <C>
BUILDING:                               Riverfront Office Park
                                        One Main Street
                                        Cambridge, Massachusetts 02142

LANDLORD:                               RREEF AMERICA REIT II CORP. PPP,
                                        a Maryland corporation

LANDLORD'S ADDRESS:                     c/o RREEF Management Company
                                        One Main Street
                                        Cambridge, MA 02142

WIRE INSTRUCTIONS AND/OR ADDRESS FOR
   RENT PAYMENT:                        RREEF AMERICA REIT II CORP. PPP
                                        75 Remittance Drive
                                        Suite 6334
                                        Chicago, IL 60675-6334

LEASE REFERENCE DATE:                   APRIL 12, 2006

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

TENANT'S NOTICE ADDRESS:

   (a) As of beginning of Term:         One Main Street
                                        Suites 600 & 710
                                        Cambridge, MA 02142

   (b) Prior to beginning of Term
       (if different):                  25 First Street
                                        Cambridge, Massachusetts 02141

PREMISES ADDRESS:                       One Main Street
                                        Suites 600 & 710
                                        Cambridge, Massachusetts 02142

PREMISES RENTABLE AREA:                 Approximately 44,981 rentable sq. ft. on
                                        the 6th and 7th floors and approximately
                                        500 usable sq. ft. of storage space on
                                        the 1st floor. (for outline of Premises
                                        see Exhibit A)

SCHEDULED COMMENCEMENT DATE:            August 14, 2006

TERM OF LEASE:                          Approximately five (5) years, four (4)
                                        months and eighteen (18) days beginning
                                        on the Commencement Date and ending on
                                        the Termination Date. The period from
                                        the Commencement Date to the last day of
                                        the same month is the "Commencement
                                        Month."

TERMINATION DATE:                       December 31, 2011

                                        The last day of the sixty-fourth (64th)
                                        full calendar month after (if the
                                        Commencement Month is not a full
                                        calendar month), or from and including
                                        (if the Commencement Month is a full
                                        calendar month), the Commencement Month
</TABLE>

                                                           ---------------------
                                                           |         |         |
                                                           |         |         |
                                                           ---------------------
                                                                 Initials

                                       iii

<PAGE>

ANNUAL RENT and MONTHLY INSTALLMENT OF RENT(Article 3):

<TABLE>
<CAPTION>
        PERIOD
----------------------   RENTABLE SQUARE     ANNUAL RENT                     MONTHLY INSTALLMENT
   FROM       THROUGH        FOOTAGE       PER SQUARE FOOT    ANNUAL RENT          OF RENT
---------   ----------   ---------------   ---------------   -------------   -------------------
<S>         <C>          <C>               <C>               <C>             <C>
8/14/2006   12/31/2007        44,981            $31.25       $1,405,656.25       $117,138.02
 1/1/2008   12/31/2008        44,981            $32.25       $1,450,637.25       $120,886.44
 1/1/2009   12/31/2009        44,981            $33.25       $1,495,618.25       $124,634.85
 1/1/2010   12/31/2010        44,981            $34.25       $1,540,599.25       $128,383.27
 1/1/2011   12/31/2011        44,981            $35.25       $1,585,580.25       $132,131.69
</TABLE>

plus for the 1st floor storage space totaling 500 usable square feet, from the
Commencement Date through the Termination Date, at a rent of $15.00 per usable
square foot, Annual Rent of $7,500.00 with Monthly Installment of Rent of
$625.00, with no share of Expenses, Taxes or insurance Costs applicable thereto.

LEASE YEAR 1 IS THE PERIOD BEGINNING ON THE COMMENCEMENT DATE AND ENDING AT THE
END OF THE SIXTEENTH (16TH) FULL CALENDAR MONTH OF THE TERM; LEASE YEAR 2 IS THE
TWELVE (12) CALENDAR MONTH PERIOD IMMEDIATELY FOLLOWING LEASE YEAR 1; LEASE YEAR
3 IS THE TWELVE (12) CALENDAR MONTH IMMEDIATELY FOLLOWING LEASE YEAR 2; AND SO
FORTH. PROVIDED THAT TENANT IS NOT THEN IN DEFAULT, THE MONTHLY INSTALLMENT OF
RENT WILL BE ABATED TO AND THROUGH 12/31/2006 IF THE COMMENCEMENT DATE IS
8/14/2006 AND, IF THE COMMENCEMENT DATE IS LATER THAN 8/14/2006, THE MONTHLY
INSTALLMENT OF RENT WILL BE ABATED TO AND THROUGH 1/31/2007. THE ACTUAL DATES
ARE TO BE CONFIRMED PER SECTION 2.1.

ALL RENTAL AMOUNTS ARE NET OF TENANT ELECTRICITY.

<TABLE>
<S>                                  <C>
BASE YEAR (EXPENSES):                2007

BASE YEAR (INSURANCE):               2007

BASE YEAR (TAXES):                   Taxes for July 1, 2006 to June 30, 2007

TENANT'S PROPORTIONATE SHARE:        13.9594%

SECURITY DEPOSIT:                    Initially $738,193.50 in the form of an
                                     irrevocable letter of credit to be reduced
                                     as set forth in Article 5.

ASSIGNMENT/SUBLETTING FEE:           $750.00

AFTER-HOURS HVAC COST:               $1.00 per heat pump per hour with a minimum
                                     charge of $30.00 per request, subject to
                                     change at any time to reflect actual cost
                                     increases to Landlord.

PARKING                              45 passes at $200.00 per space per month
                                     (see Article 39)

REAL ESTATE BROKER DUE COMMISSION:   Cushman & Wakefield of Massachusetts, Inc.,
                                     for Landlord; The Columbia Group, for
                                     Tenant

TENANT'S SIC CODE:                   7371
</TABLE>

                                                           ---------------------
                                                           |         |         |
                                                           |         |         |
                                                           ---------------------
                                                                 Initials

                                       iv

<PAGE>

<TABLE>
<S>                                  <C>
BUILDING BUSINESS HOURS:             Monday through Friday 8:00 a.m. - 6:00 p.m.
                                     (excluding Massachusetts state holidays)
                                     Saturday 8:00 a.m. - 12:00 p.m.

AMORTIZATION RATE:                   Ten percent (10%)
</TABLE>

The Reference Pages information is incorporated into and made a part of the
Lease. In the event of any conflict between any Reference Pages information and
the Lease, the Lease shall control. This Lease includes Exhibits A through F,
all of which are made a part of this Lease.

LANDLORD:                                  TENANT:

RREEF AMERICA REIT II CORP. PPP,           ART TECHNOLOGY GROUP, INC.,
a Maryland corporation                     a Delaware corporation

By: RREEF Management Company,
    a Delaware corporation,
    Authorized Agent

By: /s/ David F. Crane                     By: /s/ Julie M.B. Bradley
    ------------------------------------       ---------------------------------
Name: David F. Crane                       Name:
                                                 -------------------------------
Title: Vice President - District Manager   Title:
                                                  ------------------------------
Dated:              , 2006                 Dated:              , 2006
       -------------                              -------------

                                                           ---------------------
                                                           |         |         |
                                                           |         |         |
                                                           ---------------------
                                                                 Initials

                                        v

<PAGE>

                                      LEASE

     By this Lease Landlord leases to Tenant and Tenant leases from Landlord the
Premises in the Building as set forth and described on the Reference Pages. The
Premises are depicted on the floor plan attached hereto as Exhibit A, and the
Building is depicted on the site plan attached hereto as Exhibit A-1. The
Building is located on the Lot legally described on Exhibit A-2. The Reference
Pages, including all terms defined thereon, are incorporated as part of this
Lease.

1. USE AND RESTRICTIONS ON USE.

     1.1 The Premises are to be used solely for general office and storage
purposes. Tenant shall not do or permit anything to be done in or about the
Premises which will in any way obstruct or interfere with the rights of other
tenants or occupants of the Building or injure, or create a nuisance to them, or
allow the Premises to be used for any unlawful purpose, or commit any waste.
Tenant shall not do, permit or suffer in, on, or about the Premises the sale of
any alcoholic liquor without the written consent of Landlord first obtained.
Tenant shall comply with all governmental laws, ordinances and regulations
applicable to the use of the Premises and its occupancy and shall promptly
comply with all governmental orders and directions for the correction,
prevention and abatement of any violations in the Building or appurtenant land,
caused or permitted by, or resulting from the specific use by Tenant, or in or
upon, or in connection with, the Premises, all at Tenant's sole expense. Tenant
shall not do or permit anything to be done on or about the Premises or bring or
keep anything into the Premises which will in any way increase the rate of,
invalidate or prevent the procuring of any insurance protecting against loss or
damage to the Building or any of its contents by fire or other casualty or
against liability for damage to property or injury to persons in or about the
Building or any part thereof.

     1.2 Tenant shall not, and shall not direct, suffer or permit any of its
agents, contractors, employees, licensees or invitees (collectively, the "Tenant
Entities") to at any time handle, use, manufacture, store or dispose of in or
about the Premises or the Building any (collectively "Hazardous Materials")
flammables, explosives, radioactive materials, hazardous wastes or materials,
toxic wastes or materials, or other similar substances, petroleum products or
derivatives or any substance subject to regulation by or under any federal,
state and local laws and ordinances relating to the protection of the
environment or the keeping, use or disposition of environmentally hazardous
materials, substances, or wastes, presently in effect or hereafter adopted, all
amendments to any of them, and all rules and regulations issued pursuant to any
of such laws or ordinances (collectively "Environmental Laws"), nor shall Tenant
suffer or permit any Hazardous Materials to be used in any manner not fully in
compliance with all Environmental Laws, in the Premises or the Building and
appurtenant land or allow the environment to become contaminated with any
Hazardous Materials. Notwithstanding the foregoing, Tenant may handle, store,
use or dispose of products containing small quantities of Hazardous Materials
(such as aerosol cans containing insecticides, toner for copiers, paints, paint
remover and the like) to the extent customary and necessary for the use of the
Premises for general office purposes; provided that Tenant shall always handle,
store, use, and dispose of any such Hazardous Materials in a safe and lawful
manner and never allow such Hazardous Materials to contaminate the Premises,
Building and appurtenant land or the environment. Tenant shall protect, defend,
indemnify and hold each and all of the Landlord Entities (as defined in Article
30) harmless from and against any and all loss, claims, liability or costs
(including court costs and attorney's fees) incurred by reason of any actual or
asserted failure of Tenant to fully comply with all applicable Environmental
Laws, or the presence, handling, use or disposition in or from the Premises of
any Hazardous Materials by Tenant or any Tenant Entity (even though permissible
under all applicable Environmental Laws or the provisions of this Lease), or by
reason of any actual or asserted failure of Tenant to keep, observe, or perform
any provision of this Section 1.2.

     1.3 The Tenant shall have, as appurtenant to the Premises, rights to use in
common with others entitled thereto:

          1.3.1 the common facilities included in the Building or the Lot,
including common walkways, driveways, lobbies, hallways, ramps, stairways and
elevators;

          1.3.2 subject to Article 39, the parking facility (including the
visitor's parking area and parking spaces reserved for the disabled), at
locations which may from time to time be designated by Landlord. Use of the

<PAGE>

parking facility shall be subject to the right of the Landlord to restrict
parking during snowplowing operations, and during repair, maintenance and
restriping work affecting the parking area;

          1.3.3 the pipes, ducts, conduits, wires and appurtenant equipment
serving the Premises; and

          1.3.4 if the Premises include less than the entire rentable area of
any floor, the common toilets in the central core area of such floor.

Such rights shall always be subject to the Rules and Regulations set forth in
Exhibit D as the same may be reasonably amended by the Landlord from time to
time, and such other reasonable rules and regulations from time to time
established by Landlord by suitable notice, all of which shall be generally
applicable to all tenants of the Building and consistently applied by Landlord,
and to the right of Landlord to designate and change from time to time areas and
facilities so to be used, provided such designations and changes do not deprive
Tenant of the substantive benefits of such areas and facilities.

Not included in the Premises are the ceiling, the floor and all perimeter walls
of the space identified in Exhibit A, except the inner surfaces thereof and the
perimeter doors and windows. Tenant agrees that Landlord shall have the right to
place in the Premises (but in such manner as not unreasonably to interfere with
Tenant's use of the Premises) utility lines, telecommunication lines, shafts,
pipes and the like, for the use and benefit of Landlord and other tenants in the
Building, and to replace and maintain and repair such lines, pipes and the like,
in, over and upon the Premises, provided that such lines, shafts, pipes and the
like do not reduce the total rentable square footage of the Premises, and
further provided that Landlord shall replace, maintain and repair such lines,
shafts and pipes at a time and in a manner which minimizes any adverse impact on
Tenant's use and enjoyment of the Premises. Such utility lines, pipes and the
like, shall not be deemed part of the Premises under this Lease.

2. TERM.

     2.1 The Term of this Lease shall begin on the date ("Commencement Date")
which shall be the later of the Scheduled Commencement Date as shown on the
Reference Pages and the date that Landlord shall tender possession of the
Premises to Tenant, and shall terminate on the date as shown on the Reference
Pages ("Termination Date"), unless sooner terminated by the provisions of this
Lease. Landlord shall tender possession of the Premises with all the Landlord's
Work as defined in Exhibit B to this Lease Substantially Completed (as defined
in Exhibit B. Upon Landlord's tender of possession, Landlord and Tenant shall
agree upon a punch list of items to complete Landlord's Work and Landlord shall
proceed with due diligence and complete all such punch list items, subject to
force majeure, within thirty (30) days thereafter. Tenant shall, at Landlord's
request, execute and deliver a memorandum agreement provided by Landlord in the
form of Exhibit C attached hereto, setting forth the actual Commencement Date,
Termination Date and, if necessary, a revised rent schedule. Should Tenant fail
to do so within thirty (30) days after Landlord's request, the information set
forth in such memorandum provided by Landlord shall be conclusively presumed to
be agreed and correct, unless there is a bona fide dispute regarding the
accuracy of such information.

     2.2 Tenant agrees that in the event of the inability of Landlord to deliver
possession of the Premises on the Scheduled Commencement Date for any reason,
Landlord shall not be liable for any damage resulting from such inability, but
Tenant shall not be liable for any rent until the time when Landlord can, after
notice to Tenant, deliver possession of the Premises to Tenant. No such failure
to give possession on the Scheduled Commencement Date shall affect the other
obligations of Tenant under this Lease, except that if Landlord is unable to
deliver possession of the Premises on or before October 15, 2006, Tenant shall
have the option to terminate this Lease unless said delay is as a result of: (a)
Tenant's request for materials, finishes or installations other than Landlord's
standard except those, if any, that Landlord shall have expressly agreed to
furnish without extension of time agreed by Landlord; (b) Tenant's change in any
plans or specifications; or, (c) performance or completion by a party employed
by Tenant (each of the foregoing, a "Tenant Delay"). If any delay is the result
of a Tenant Delay, the Commencement Date and the payment of rent under this
Lease shall be accelerated by the number of days of such Tenant Delay.

                                       2

<PAGE>

     2.3 In the event Landlord permits Tenant, or any agent, employee or
contractor of Tenant, to enter, use or occupy the Premises prior to the
Commencement Date, such entry, use or occupancy shall be subject to all the
provisions of this Lease other than the payment of rent, including, without
limitation, Tenant's compliance with the insurance requirements of Article 11.
Said early possession shall not advance the Termination Date.

     2.4 At Tenant's election, the Term of this Lease may be extended in
accordance with Article 40 of this Lease.

3. RENT.

     3.1 Tenant agrees to pay to Landlord the Annual Rent in effect from time to
time by paying the Monthly Installment of Rent then in effect on or before the
first day of each full calendar month during the Term. The Monthly Installment
of Rent in effect at any time shall be one-twelfth (1/12) of the Annual Rent in
effect at such time. Rent for any period during the Term which is less than a
full month shall be a prorated portion of the Monthly Installment of Rent based
upon the number of days in such month. Said rent shall be paid to Landlord,
without deduction or offset and without notice or demand, at the Rent Payment
Address, as set forth on the Reference Pages, or to such other person or at such
other place as Landlord may from time to time designate in writing. If an Event
of Default occurs, Landlord may require by notice to Tenant that all subsequent
rent payments be made by an automatic payment from Tenant's bank account to
Landlord's account, without cost to Landlord. Tenant must implement such
automatic payment system prior to the next scheduled rent payment or within ten
(10) days after Landlord's notice, whichever is later. Unless specified in this
Lease to the contrary, all amounts and sums payable by Tenant to Landlord
pursuant to this Lease shall be deemed additional rent.

     3.2 Tenant recognizes that late payment of any Monthly Installment of Rent
or other sum invoiced by Landlord under this Lease will result in administrative
expense to Landlord, the extent of which additional expense is extremely
difficult and economically impractical to ascertain. Tenant therefore agrees
that if rent or any other sum is not paid when due and payable pursuant to this
Lease, a late charge shall be imposed in an amount equal to the greater of: (a)
Fifty Dollars ($50.00), or (b) five percent (5%) of the unpaid rent or other
payment. The amount of the late charge to be paid by Tenant shall be reassessed
and added to Tenant's obligation for each successive month until paid. The
provisions of this Section 3.2 in no way relieve Tenant of the obligation to pay
rent or other payments on or before the date on which they are due, nor do the
terms of this Section 3.2 in any way affect Landlord's remedies pursuant to
Article 19 of this Lease in the event said rent or other payment is unpaid after
date due.

4. RENT ADJUSTMENTS.

     4.1 For the purpose of this Article 4, the following terms are defined as
follows:

          4.1.1 LEASE YEAR: Each fiscal year (as determined by Landlord from
time to time) falling partly or wholly within the Term, as set forth on the
Reference Pages.

          4.1.2 EXPENSES: All costs of operation, maintenance, repair,
replacement and management of the Building (including the amount of any credits
which Landlord may grant to particular tenants of the Building in lieu of
providing any standard services or paying any standard costs described in this
Section 4.1.2 for similar tenants), as determined in accordance with generally
accepted accounting principles, including the following costs by way of
illustration, but not limitation: water and sewer charges; utility costs,
including, but not limited to, the cost of heat, light, power, steam, gas; waste
disposal; the cost of janitorial services; the cost of security and alarm
services (including any central station signaling system); costs of cleaning,
repairing, replacing and maintaining the common areas, including parking and
landscaping, window cleaning costs; labor costs; costs and expenses of managing
the Building including management and/or administrative fees (provided that any
such fees paid to entities related to or affiliated with Landlord shall not
exceed fees generally paid in an arms-length transaction for similar services in
the Cambridge or suburban Boston office market); air conditioning maintenance
costs; elevator maintenance fees and supplies; costs of materials used in the
maintenance of the Building; costs of maintaining, repairing, and servicing
equipment used in connection with the maintenance of the Building, including the
cost of maintenance, repair and service agreements and rental and leasing costs;
purchase costs of equipment used in

                                       3

<PAGE>

connection with the maintenance of the Building; current rental and leasing
costs of items which would be capital items if purchased; tool costs; licenses,
permits and inspection fees; wages and salaries; employee benefits and payroll
taxes; accounting and legal fees; any sales, use or service taxes incurred in
connection therewith. In addition, Landlord shall be entitled to recover, as
additional rent (which, along with any other capital expenditures constituting
Expenses, Landlord may either include in Expenses or cause to be billed to
Tenant along with Expenses and Taxes but as a separate item), Tenant's
Proportionate Share of: (i) an allocable portion of the cost of capital
improvement items which are reasonably calculated to reduce operating expenses;
(ii) the cost of fire sprinklers and suppression systems and other life safety
systems; and (iii) other capital expenses which are required under any
governmental laws, regulations or ordinances which were not applicable to the
Building at the time it was constructed; provided such costs shall be amortized
over the reasonable life of such expenditures in accordance with such reasonable
life and amortization schedules as shall be determined by Landlord in accordance
with generally accepted accounting principles, with interest on the unamortized
amount at one percent (1%) in excess of the Wall Street Journal prime lending
rate announced from time to time. Expenses shall not include Taxes, Insurance
Costs; the cost of capital improvements (except as set forth above);
depreciation; human resources support, or any other home office costs; salaries
or fringe benefits of personnel above the grade of building/property manager;
compensation paid to any Building employee to the extent that the same is not
fairly allocable to the work or service provided by such employee to the
Building; debt service, late charges, points, fee title insurance or mortgagee
title insurance, escrow or similar charges under any mortgage on the Property;
the costs of repairs or other work to the extent Landlord is reimbursed by
insurance or condemnation proceeds; costs in connection with leasing space in
the Building, including brokerage commissions; lease concessions, marketing and
advertising; rental abatements and construction allowances granted to specific
tenants; costs incurred in connection with the sale, financing or refinancing of
the Building; services or other benefits provided by Landlord to other tenants
of the Building to the extent such services or other benefits are in excess of
the services which Landlord furnishes or is required to furnish to Tenant under
this Lease at Landlord's initial expense; fines, interest and penalties incurred
due to the late payment of Taxes or Expenses; organizational expenses associated
with the creation and operation of the entity which constitutes Landlord; costs
incurred in connection with Landlord's enforcement of lease with tenants in the
Building, including, without limitation, administrative hearings, court costs
and attorneys' fees and disbursements in connection with any summary proceeding
to dispossess any tenant; the cost of installing, operating and maintaining any
specialty facility such as an observatory, broadcasting facilities, luncheon
club, athletic or recreational club, child care or similar facility, auditorium,
or conference center; charitable contributions or other donations; costs
attributable to the removal of asbestos-containing materials or lead paint or
other hazardous materials; or any penalties or damages that Landlord pay s to
Tenant under this Lease or to other tenants in the Building under their
respective leases; costs attributable to the gross negligence or willful
misconduct of Landlord or its agents or contractors.

          4.1.3 TAXES: Real estate taxes and any other taxes, charges and
assessments which are levied with respect to the Building or the land
appurtenant to the Building, or with respect to any improvements, fixtures and
equipment or other property of Landlord, real or personal, located in the
Building and used in connection with the operation of the Building and said
land, any payments to any ground lessor in reimbursement of tax payments made by
such lessor; and all fees, expenses and costs incurred by Landlord in
investigating, protesting, contesting or in any way seeking to reduce or avoid
increase in any assessments, levies or the tax rate pertaining to any Taxes to
be paid by Landlord in any Lease Year. Taxes shall not include any corporate
franchise, or estate, inheritance or net income tax, gift tax, sales tax or tax
imposed upon any transfer by Landlord of its interest in this Lease or the
Building or any taxes to be paid by Tenant pursuant to Article 28.

          4.1.4 INSURANCE COSTS: Any and all insurance charges of or relating to
all insurance policies and endorsements deemed by Landlord to be reasonably
necessary or desirable and relating in any manner to the protection,
preservation, or operation of the Building or any part thereof; provided that if
any such insurance policies provide coverage for any assets in addition to the
Building and the fixtures and equipment therein, then the costs of such policies
shall be ratably allocated among the insured assets.

     4.2 If in any Lease Year, (i) Expenses paid or incurred shall exceed
Expenses paid or incurred in the Base Year (Expenses) and/or (ii) Taxes paid or
incurred by Landlord in any Lease Year shall exceed the amount of such Taxes
which became due and payable in the Base Year (Taxes), and/or (iii) Insurance
Costs paid or incurred by Landlord in any Lease Year shall exceed the amount of
such Insurance Costs which became due and payable in the

                                       4

<PAGE>

Base Year (Insurance), Tenant shall pay as additional rent for such Lease Year
Tenant's Proportionate Share of each such excess amount.

     4.3 The annual determination of Expenses and Insurance Costs shall be made
by Landlord and shall be binding upon Landlord and Tenant, subject to the
provisions of this Section 4.3. During the Term, Tenant may review, at Tenant's
sole cost and expense, the books and records supporting such determination in an
office of Landlord, or Landlord's agent, at the Building, during normal business
hours, upon giving Landlord five (5) days advance written notice within one
hundred twenty (120) days after receipt of such determination, but in no event
more often than once in any one (1) year period, subject to execution of a
confidentiality agreement acceptable to Landlord, and provided that if Tenant
utilizes its financing department or an independent accountant to perform such
review it shall not compensated on a contingency basis and is also subject to
such confidentiality agreement. If Tenant fails to object to Landlord's
determination of Expenses and Insurance Costs within ninety (90) days after
receipt, or if any such objection fails to state with specificity the reason for
the objection, Tenant shall be deemed to have approved such determination and
shall have no further right to object to or contest such determination. In the
event that during all or any portion of any Lease Year or Base Year, the
Building is not fully rented and occupied Landlord shall make an appropriate
adjustment in occupancy-related Expenses for such year for the purpose of
avoiding distortion of the amount of such Expenses to be attributed to Tenant by
reason of variation in total occupancy of the Building, by employing consistent
and sound accounting and management principles to determine Expenses that would
have been paid or incurred by Landlord had the Building been one hundred percent
(100%) rented and occupied, and the amount so determined shall be deemed to have
been Expenses for such Lease Year. In the event Tenant has been overcharged for
Expenses and/or Taxes and such overcharge is ten percent (10%) or more of the
amount actually due from Tenant with respect to Expenses or Taxes, as the case
may be, Landlord shall also pay all reasonable costs incurred by Tenant in
conducting the audit.

     4.4 Prior to the actual determination thereof for a Lease Year, Landlord
may from time to time estimate Tenant's liability for Expenses, Insurance Costs
and/or Taxes under Section 4.1, Article 6 and Article 28 for the Lease Year or
portion thereof. Landlord will give Tenant written notification of the amount of
such estimate and Tenant agrees that it will pay, by increase of its Monthly
Installments of Rent due in such Lease Year, additional rent in the amount of
such estimate. Any such increased rate of Monthly Installments of Rent pursuant
to this Section 4.4 shall remain in effect until further written notification to
Tenant pursuant hereto.

     4.5 When the above mentioned actual determination of Tenant's liability for
Expenses, Insurance Costs and/or Taxes is made for any Lease Year and when
Tenant is so notified in writing, then:

          4.5.1 If the total additional rent Tenant actually paid pursuant to
Section 4.3 on account of Expenses, Insurance Costs and/or Taxes for the Lease
Year is less than Tenant's liability for Expenses, Insurance Costs and/or Taxes,
then Tenant shall pay such deficiency to Landlord as additional rent in one lump
sum within thirty (30) days of receipt of Landlord's bill therefor; and

          4.5.2 If the total additional rent Tenant actually paid pursuant to
Section 4.3 on account of Expenses, Insurance Costs and/or Taxes for the Lease
Year is more than Tenant's liability for Expenses, Insurance Costs and/or Taxes,
then Landlord shall credit the difference against the then next due payments to
be made by Tenant under this Article 4, or, if the Lease has terminated, refund
the difference in cash. Tenant shall not be entitled to a credit by reason of
actual Expenses and/or Taxes and/or Insurance Costs in any Lease Year being less
than Expenses and/or Taxes and/or Insurance Costs in the Base Year (Expenses
and/or Taxes and/or Insurance).

     4.6 If the Commencement Date is other than January 1 or if the Termination
Date is other than December 31, Tenant's liability for Expenses, Insurance Costs
and Taxes for the Lease Year in which said Date occurs shall be prorated based
upon a three hundred sixty-five (365) day year.

5. SECURITY DEPOSIT.

     5.1 Tenant shall deposit the Security Deposit with Landlord upon the
execution of this Lease. Said sum shall be held by Landlord as security for the
faithful performance by Tenant of all the terms, covenants and conditions of
this Lease to be kept and performed by Tenant and not as an advance rental
deposit or as a measure of

                                       5

<PAGE>

Landlord's damage in case of Tenant's default. If Tenant defaults with respect
to any provision of this Lease, Landlord may use any part of the Security
Deposit for the payment of any rent or any other sum in default, or for the
payment of any amount which Landlord may spend or become obligated to spend by
reason of Tenant's default, or to compensate Landlord for any other loss or
damage which Landlord may suffer by reason of Tenant's default. If any portion
is so used, Tenant shall within ten (10) business days after written demand
therefor, deposit with Landlord an amount sufficient to restore the Security
Deposit to its original amount and Tenant's failure to do so shall be a material
breach of this Lease. Except to such extent, if any, as shall be required by
law, Landlord shall not be required to keep the Security Deposit separate from
its general funds, and Tenant shall not be entitled to interest on such deposit.
If Tenant shall fully and faithfully perform every provision of this Lease to be
performed by it, the Security Deposit or any balance thereof shall be returned
to Tenant at such time after termination of this Lease when Landlord shall have
determined that all of Tenant's obligations under this Lease have been
fulfilled, but in no event more than thirty (30) days after the Termination
Date.

     5.2 The required Security Deposit shall be in the form of an Irrevocable
Standby Letter of Credit in favor of Landlord (the "letter of credit") in the
amount set forth on the Reference Pages. Under any circumstance under which
Landlord is entitled the use of all or a part of the Security Deposit, then,
Landlord, in addition to all other rights and remedies provided under the Lease,
shall have the right to draw down the full balance of the letter of credit and
retain so much of the proceeds as is required to cure the default or other
condition which gave rise to Landlord's right to draw on the letter of credit.
The following terms and conditions shall govern the letter of credit:

          5.2.1 Provided that Tenant is not then in default, the amount of the
letter of credit may be reduced after the thirtieth (30th) month of the Term to
$369,096.75. Upon expiration of the Term, the letter of credit shall be returned
to Tenant when Tenant is entitled to return of its Security Deposit.

          5.2.2 The letter of credit shall be in favor of Landlord, shall be
issued by Silicon Valley Bank or such other commercial bank as is reasonably
acceptable to Landlord, shall comply with all of the terms and conditions of
this Section 5.2 and shall otherwise be in form reasonably acceptable to
Landlord. The initial letter of credit shall have an expiration date not earlier
than fifteen (15) months after the Commencement Date. A draft of the form of
letter of credit must be submitted to Landlord for its approval prior to
issuance.

          5.2.3 The letter of credit or any replacement letter of credit shall
be irrevocable for the term thereof and shall automatically renew on a year to
year basis until a period ending not earlier than thirty (30) days after the
Termination Date ("End Date") without any action whatsoever on the part of
Landlord; provided that the issuing bank shall have the right not to renew the
letter of credit by giving written notice to Landlord not less than sixty (60)
days prior to the expiration of the then current term of the letter of credit
that it does not intend to renew the letter of credit. Tenant understands that
the election by the issuing bank not to renew the letter of credit shall not, in
any event, diminish the obligation of Tenant to maintain such an irrevocable
letter of credit in favor of Landlord through such date.

          5.2.4 Landlord, or its then managing agent, shall have the right from
time to time to make one or more draws on the letter of credit at any time that
an Event of Default has occurred and such Event of Default remains uncured five
(5) days after written notice from Landlord to Tenant. The letter of credit must
state that it can be presented for payment at the office of the issuer or an
approved correspondent in the metropolitan Boston, Massachusetts area. Funds may
be drawn down on the letter of credit upon presentation to the issuing or
corresponding bank of Landlord's (or Landlord's then managing agent's)
certificate stating as follows:

          "Beneficiary is entitled to draw on this credit pursuant to that
          certain Lease dated for reference April 12, 2006 between RREEF AMERICA
          REIT II CORP. PPP, a Maryland corporation, as Landlord and ART
          TECHNOLOGY GROUP, INC., a Massachusetts corporation, as Tenant, as
          amended from time to time."

It is understood that if Landlord or its managing agent be a corporation,
partnership or other entity, then such statement shall be signed by an officer
(if a corporation), a general partner (if a partnership), or any authorized
party (if another entity).

                                       6

<PAGE>

          5.2.5 Tenant acknowledges and agrees (and the letter of credit shall
so state) that the letter of credit shall be honored by the issuing bank without
inquiry as to the truth of the statements set forth in such draw request and
regardless of whether the Tenant disputes the content of such statement.

          5.2.6 In the event of a transfer of Landlord's interest in the
Premises, Landlord shall have the right to transfer the letter of credit to the
transferee and thereupon the Landlord shall, without any further agreement
between the parties, be released by Tenant from all liability therefor, and it
is agreed that the provisions hereof shall apply to every transfer or assignment
of said letter of credit to a new landlord; provided that Landldord shall pay
all fees to the issuer necessary to effect and evidence such transfer.

          5.2.7 Without limiting the generality of the foregoing, if the letter
of credit expires earlier than the End Date, or the issuing bank notifies
Landlord that it will not renew the letter of credit, Landlord shall accept a
renewal thereof or substitute letter credit (such renewal or substitute letter
of credit to be in effect not later than thirty (30) days prior to the
expiration of the expiring letter of credit), irrevocable and automatically
renewable as above provided to the End Date upon the same terms as the expiring
letter of credit or upon such other terms as may be acceptable to Landlord.
However, if (i) the letter of credit is not timely renewed, or (ii) a substitute
letter of credit, complying with all of the terms and conditions of this Section
is not timely received, then Landlord may present the expiring letter of credit
to the issuing bank, and the entire sum so obtained shall be paid to Landlord,
to be held by Landlord until Tenant would otherwise be entitled to the return of
the letter of credit, and if a monetary default occurs, Landlord may retain so
much of the proceeds as are necessary to cure such monetary default.
Notwithstanding anything to the contrary in this Section 5, Tenant shall not be
in default for failing to renew the letter of credit unless such failure to
renew remains uncured five (5) days after written notice from Landlord.

6. ALTERATIONS.

     6.1 Except for those, if any, specifically provided for in Exhibit B to
this Lease, Tenant shall not make or suffer to be made any alterations,
additions, or improvements, including, but not limited to, the attachment of any
fixtures or equipment in, on, or to the Premises or any part thereof or the
making of any improvements as required by Article 7, without the prior written
consent of Landlord, which consent for non-structural alterations, additions or
improvements shall not be unreasonably withheld. When applying for such consent,
Tenant shall, if requested by Landlord, furnish complete plans and
specifications for such alterations, additions and improvements. Provided Tenant
gives Landlord advanced written notice, Landlord's consent shall not be required
with respect to alterations which (i) are not structural in nature, (ii) are not
visible from the exterior of the Building, (iii) do not affect or require
modification of the Building's electrical, mechanical, plumbing, HVAC or other
systems, and (iv) in aggregate do not cost more than $25,000.00.

     6.2 In the event Landlord consents to the making of any such alteration,
addition or improvement by Tenant, the same shall be made by using either
Landlord's contractor or a contractor reasonably approved by Landlord, in either
event at Tenant's sole cost and expense. If Tenant shall employ any contractor
other than Landlord's contractor and such other contractor or any subcontractor
of such other contractor shall employ any non-union labor or supplier, Tenant
shall be responsible for and hold Landlord harmless from any and all delays,
damages and extra costs suffered by Landlord as a result of any dispute with any
labor unions concerning the wage, hours, terms or conditions of the employment
of any such labor. In any event Landlord may charge Tenant a construction
management fee not to exceed (i) five percent (5%) of the cost of such work,
which cost exceeds $25,000.00 but is less than $100,000.00; (ii) three percent
(3%) of the cost of such work, which cost is within the range of $100,000.00 up
to, but not including, $500,000.00; and (iii) two percent (2%) of the cost of
such work, which cost is $500,000.00 or greater to cover its overhead as it
relates to such proposed work, plus third-party costs actually incurred by
Landlord in connection with the proposed work and the design thereof, with all
such amounts being due five (5) days after Landlord's demand.

     6.3 All alterations, additions or improvements proposed by Tenant shall be
constructed in accordance with all government laws, ordinances, rules and
regulations, using Building standard materials where applicable, and Tenant
shall, prior to construction, provide the additional insurance required under
Article 11 in such case, and also all such assurances to Landlord as Landlord
shall reasonably require to assure payment of the costs thereof, including but
not limited to, notices of non-responsibility, waivers of lien, surety company
performance bonds and

                                       7

<PAGE>

funded construction escrows and to protect Landlord and the Building and
appurtenant land against any loss from any mechanic's, materialmen's or other
liens. Tenant shall pay in addition to any sums due pursuant to Article 4, any
increase in real estate taxes attributable to any such alteration, addition or
improvement for so long, during the Term, as such increase is ascertainable; at
Landlord's election said sums shall be paid in the same way as sums due under
Article 4. Landlord may, as a condition to its consent to any particular
alterations or improvements, require Tenant to deposit with Landlord the amount
reasonably estimated by Landlord as sufficient to cover the cost of removing
such alterations or improvements and restoring the Premises, to the extent
required under Section 26.2.

7. REPAIR.

     7.1 Landlord shall have no obligation to alter, remodel, improve, repair,
decorate or paint the Premises, except as specified in Exhibit B if attached to
this Lease and except that Landlord shall repair and maintain the structural
portions of the Building, including the basic plumbing, air conditioning,
heating and electrical systems installed or furnished by Landlord. By taking
possession of the Premises, Tenant accepts them as being in good order,
condition and repair and in the condition in which Landlord is obligated to
deliver them, except as set forth in the punch list to be delivered pursuant to
Section 2.1. It is hereby understood and agreed that no representations
respecting the condition of the Premises or the Building have been made by
Landlord to Tenant, except as specifically set forth in this Lease.

     7.2 Tenant shall, at all times during the Term, keep the Premises in good
condition and repair excepting damage by fire, or other casualty, and in
compliance with all applicable governmental laws, ordinances and regulations,
promptly complying with all governmental orders and directives for the
correction, prevention and abatement of any violations or nuisances in or upon,
or connected with, the Premises, all at Tenant's sole expense.

     7.3 Landlord shall not be liable for any failure to make any repairs or to
perform any maintenance unless such failure shall persist for an unreasonable
time after written notice of the need of such repairs or maintenance is given to
Landlord by Tenant.

     7.4 Except as provided in Article 22 and for Landlord's gross negligence or
willful misconduct, there shall be no abatement of rent and no liability of
Landlord by reason of any injury to or interference with Tenant's business
arising from the making of any repairs, alterations or improvements in or to any
portion of the Building or the Premises or to fixtures, appurtenances and
equipment in the Building. Except to the extent, if any, prohibited by law,
Tenant waives the right to make repairs at Landlord's expense under any law,
statute or ordinance now or hereafter in effect.

8. LIENS. Tenant shall keep the Premises, the Building and appurtenant land and
Tenant's leasehold interest in the Premises free from any liens arising out of
any services, work or materials performed, furnished, or contracted for by
Tenant, or obligations incurred by Tenant. In the event that Tenant fails,
within twenty (20) days following the imposition of any such lien, to either
cause the same to be released of record or provide Landlord with insurance
against the same issued by a major title insurance company or such other
protection against the same as Landlord shall accept (such failure to constitute
an Event of Default), Landlord shall have the right to cause the same to be
released by such means as it shall deem proper, including payment of the claim
giving rise to such lien. All such sums paid by Landlord and all expenses
incurred by it in connection therewith shall be payable to it by Tenant within
twenty (20) days of Landlord's written demand.

9. ASSIGNMENT AND SUBLETTING.

     9.1 Tenant shall have the right to assign or pledge this Lease or to sublet
the whole or any part of the Premises whether voluntarily or by operation of
law, or permit the use or occupancy of the Premises by anyone other than Tenant
subject to the prior written consent of Landlord, such consent not to be
unreasonably withheld conditioned or delayed, and said approval shall also be
required prior to any assignment or subletting by any and all assignees of the
Lease and subtenants of the Premises. In the event Tenant desires to sublet, or
permit such occupancy of, the Premises, or any portion thereof, or assign this
Lease, Tenant shall give written notice thereof to Landlord at least thirty (30)
days but no more than one hundred eighty (180) days prior to the proposed
commencement date of such subletting or assignment, which notice shall set forth
the name of the proposed

                                       8

<PAGE>

subtenant or assignee, the relevant terms of any sublease or assignment and
copies of financial reports and other relevant financial information of the
proposed subtenant or assignee. Landlord shall provide its approval to such
proposed assignment or sublease (or a written explanation of why such approval
is being withheld) no later than thirty (30) days after Tenant provides the
information required by this Section 9.1.

     9.2 Notwithstanding any assignment or subletting, permitted or otherwise,
Tenant shall at all times remain directly, primarily and fully responsible and
liable for the payment of the rent specified in this Lease and for compliance
with all of its other obligations under the terms, provisions and covenants of
this Lease. Upon the occurrence of an Event of Default, if the Premises or any
part of them are then assigned or sublet, Landlord, in addition to any other
remedies provided in this Lease or provided by law, may, at its option, collect
directly from such assignee or subtenant all rents due and becoming due to
Tenant under such assignment or sublease and apply such rent against any sums
due to Landlord from Tenant under this Lease, and no such collection shall be
construed to constitute a novation or release of Tenant from the further
performance of Tenant's obligations under this Lease.

     9.3 Intentionally deleted.

     9.4 In the event that Tenant sells, sublets, assigns or transfers this
Lease, Tenant shall pay to Landlord as additional rent an amount equal to fifty
percent (50%) of any Increased Rent (as defined below), less Tenant's Costs (as
defined below), when and as such Increased Rent is received by Tenant. As used
in this Section, "Increased Rent" shall mean the excess of (i) all rent and
other consideration which Tenant is entitled to receive by reason of any sale,
sublease, assignment or other transfer of this Lease, over (ii) the rent
otherwise payable by Tenant under this Lease at such time. For purposes of the
foregoing, any consideration received by Tenant in form other than cash shall be
valued at its fair market value as determined by Landlord in good faith. For
purposes of this Section 9.4, the term "Tenant's Costs' shall mean commissions,
allowances, tenant improvements, legal fees and all other reasonable costs,
calculated on a cash basis, incurred by Tenant in connection with such sublease,
assignment or other transfer.

     9.5 Notwithstanding any other provision hereof, it shall be considered
reasonable for Landlord to withhold its consent to any assignment of this Lease
or sublease of any portion of the Premises if at the time of either Tenant's
notice of the proposed assignment or sublease or the proposed commencement date
thereof, there shall exist any uncured default of Tenant or matter which will
become a default of Tenant with passage of time unless cured, or if the proposed
assignee or sublessee is an entity: (a) with which Landlord is already in
negotiation; (b) is already an occupant of the Park unless Landlord is unable to
provide the amount of space required by such occupant; (c) is a governmental
agency; (d) is incompatible with the character of occupancy of the Building; (e)
with which the payment for the sublease or assignment is determined in whole or
in part based upon its net income or profits; or (f) would subject the Premises
to a use which would: (i) involve increased wear upon the Building; (ii) violate
any exclusive right granted to another tenant of the Building; (iii) require any
addition to or modification of the Premises or the Building in order to comply
with building code or other governmental requirements (unless such addition or
modification is made at the expense of Tenant or the proposed assignee or
sublessee; or, (iv) involve a violation of Section 1.2. Tenant expressly agrees
that for the purposes of any statutory or other requirement of reasonableness on
the part of Landlord, Landlord's refusal to consent to any assignment or
sublease for any of the reasons described in this Section 9.5, shall be
conclusively deemed to be reasonable.

     9.6 Upon any request to assign or sublet, Tenant will pay to Landlord the
Assignment/Subletting Fee plus, on demand, a sum equal to all of Landlord's
out-of-pocket costs, including reasonable attorney's fees, incurred in
investigating and considering any proposed or purported assignment or pledge of
this Lease or sublease of any of the Premises, regardless of whether Landlord
shall consent to, refuse consent, or determine that Landlord's consent is not
required for, such assignment, pledge or sublease. Any purported sale,
assignment, mortgage, transfer of this Lease or subletting which does not comply
with the provisions of this Article 9 shall be void.

     9.7 If Tenant is a corporation, limited liability company, partnership or
trust, any transfer or transfers of or change or changes within any twelve (12)
month period in the number of the outstanding voting shares of the corporation
or limited liability company, the general partnership interests in the
partnership or the identity of the persons or entities controlling the
activities of such partnership or trust resulting in the persons or entities
owning or controlling a majority of such shares, partnership interests or
activities of such partnership or trust at the beginning

                                       9

<PAGE>

of such period no longer having such ownership or control shall be regarded as
equivalent to an assignment of this Lease to the persons or entities acquiring
such ownership or control and shall be subject to all the provisions of this
Article 9 to the same extent and for all intents and purposes as though such an
assignment.

     9.8 Notwithstanding the foregoing provisions of this Article to the
contrary, Tenant shall be permitted to assign this Lease, or sublet all or a
portion of the Premises, to an Affiliate of Tenant without the prior consent of
Landlord, if all of the following conditions are first satisfied:

          9.8.1 Tenant shall not then be in default under this Lease;

          9.8.2 a fully executed copy of such assignment or sublease, the
assumption of this Lease by the assignee or acceptance of the sublease by the
sublessee, and such other information regarding the assignment or sublease as
Landlord may reasonably request, shall have been delivered to Landlord;

          9.8.3 the Premises shall continue to be operated solely for the use
specified in the Reference Page or other use acceptable to Landlord in its sole
discretion;

          9.8.4 any guarantor of this Lease reaffirms that its Guaranty remains
in full force and effect; and

          9.8.5 Tenant shall pay all costs reasonably incurred by Landlord in
connection with such assignment or subletting, including without limitation
attorneys' fees.

Tenant acknowledges (and, at Landlord's request, at the time of such assignment
or subletting shall confirm) that in each instance Tenant shall remain liable
for performance of the terms and conditions of the Lease despite such assignment
or subletting. As used herein the term "Affiliate" shall mean an entity which
(i) directly or indirectly controls Tenant or (ii) is under the direct or
indirect control of Tenant or (iii) is under common direct or indirect control
with Tenant, (iv) is the successor in interest to Tenant by way of merger or
consolidation, or by sale of all of the stock of Tenant or of all of the assets
of Tenant, so long as the tangible net worth of the surviving or successor
entity following such transaction is at least as much as the tangible net worth
of Tenant immediately preceding the transaction or at the Commencement Date,
whichever is higher. Control shall mean ownership of fifty-one percent (51%) or
more of the voting securities or rights of the controlled entity.

10. INDEMNIFICATION. None of the Landlord Entities shall be liable and Tenant
hereby waives all claims against them for any damage to any property or any
injury to any person in or about the Premises or the Building by or from any
cause whatsoever (including without limiting the foregoing, rain or water
leakage of any character from the roof, windows, walls, basement, pipes,
plumbing works or appliances, the Building not being in good condition or
repair, gas, fire, oil, electricity or theft), except to the extent caused by or
arising from the gross negligence or willful misconduct of Landlord or its
agents, employees or contractors. Tenant shall protect, indemnify and hold the
Landlord Entities harmless from and against any and all loss, claims, liability
or costs (including court costs and attorney's fees) incurred by reason of (a)
any damage to any property (including but not limited to property of any
Landlord Entity) or any injury (including but not limited to death) to any
person occurring in, on or about the Premises or the Building to the extent that
such injury or damage shall be caused by or arise from any actual or alleged
act, neglect, fault, or omission by or of Tenant or any Tenant Entity to meet
any standards imposed by any duty with respect to the injury or damage; (b) the
conduct or management of any work or thing whatsoever done by the Tenant in or
about the Premises or from transactions of the Tenant concerning the Premises;
(c) Tenant's failure to comply with any and all governmental laws, ordinances
and regulations applicable to the condition or use of the Premises or its
occupancy; or (d) any breach or default on the part of Tenant in the performance
of any covenant or agreement on the part of the Tenant to be performed pursuant
to this Lease. The provisions of this Article shall survive the termination of
this Lease with respect to any claims or liability accruing prior to such
termination.

11. INSURANCE.

     11.1 Tenant shall keep in force throughout the Term: (a) a Commercial
General Liability insurance policy or policies to protect the Landlord Entities
against any liability to the public or to any invitee of Tenant or a

                                       10

<PAGE>

Landlord Entity incidental to the use of or resulting from any accident
occurring in or upon the Premises with a limit of not less than $1,000,000.00
per occurrence and not less than $2,000,000.00 in the annual aggregate, or such
larger amount as Landlord may prudently require from time to time that would be
within the range of coverage for like kind of buildings in the Boston
marketplace, covering bodily injury and property damage liability and $1,000,000
products/completed operations aggregate; (b) Business Auto Liability covering
owned, non-owned and hired vehicles with a limit of not less than $1,000,000 per
accident; (c) Worker's Compensation Insurance with limits as required by statute
and Employers Liability with limits of $500,000 each accident, $500,000 disease
policy limit, $500,000 disease--each employee; (d) All Risk or Special Form
coverage protecting Tenant against loss of or damage to Tenant's alterations,
additions, improvements, carpeting, floor coverings, panelings, decorations,
fixtures, inventory and other business personal property situated in or about
the Premises to the full replacement value of the property so insured; and, (e)
Business Interruption Insurance with limit of liability representing loss of at
least approximately six (6) months of income.

     11.2 The aforesaid policies shall (a) be provided at Tenant's expense; (b)
name the Landlord Entities as additional insureds (General Liability) and loss
payee (Property--Special Form); (c) be issued by an insurance company with a
minimum Best's rating of "A-:VII" during the Term; and (d) provide that said
insurance shall not be canceled unless thirty (30) days prior written notice
(ten days for non-payment of premium) shall have been given to Landlord; a
certificate of Liability insurance on Accord Form 25 and a certificate of
Property insurance on Accord Form 27, or comparable forms, shall be delivered to
Landlord by Tenant upon the Commencement Date and at least thirty (30) days
prior to each renewal of said insurance.

     11.3 Whenever Tenant shall undertake any alterations, additions or
improvements in, to or about the Premises ("Work") the aforesaid insurance
protection must extend to and include injuries to persons and damage to property
arising in connection with such Work, without limitation including liability
under any applicable structural work act, and such other insurance as Landlord
shall reasonably require; and the policies of or certificates evidencing such
insurance must be delivered to Landlord prior to the commencement of any such
Work.

12. WAIVER OF SUBROGATION. So long as their respective insurers so permit,
Tenant and Landlord hereby mutually waive their respective rights of recovery
against each other for any loss insured by fire, extended coverage, All Risks or
other insurance now or hereafter existing for the benefit of the respective
party but only to the extent of the net insurance proceeds payable under such
policies. Each party shall obtain any special endorsements required by their
insurer to evidence compliance with the aforementioned waiver.

13. SERVICES AND UTILITIES.

     13.1 Subject to the other provisions of this Lease, Landlord agrees to
furnish to the Premises during Building Business Hours (specified on the
Reference Pages) on generally recognized business days (but exclusive in any
event of Sundays and national and local legal holidays), the following services
and utilities subject to the rules and regulations of the Building prescribed
from time to time: (a) water suitable for normal office use of the Premises; (b)
heat and air conditioning required in Landlord's reasonable judgment for the use
and occupation of the Premises during Building Business Hours, which shall be no
colder than 68 degrees in the winter and no warmer than 76 degrees in the
summer; (c) cleaning and janitorial service; (d) elevator service by
non-attended automatic elevators; and, (e) equipment to bring to the Premises
electricity for lighting, convenience outlets and other normal office use. In
the absence of Landlord's gross negligence or willful misconduct, Landlord shall
not be liable for, and Tenant shall not be entitled to, any abatement or
reduction of rental by reason of Landlord's failure to furnish any of the
foregoing, unless such failure shall persist for an unreasonable time after
written notice of such failure is given to Landlord by Tenant and provided
further that Landlord shall not be liable when such failure is caused by
accident, breakage, repairs, labor disputes of any character, energy usage
restrictions or by any other cause, similar or dissimilar, beyond the reasonable
control of Landlord. Landlord shall use reasonable efforts to remedy any
interruption in the furnishing of services and utilities.

          13.1.1 Allocable Costs - Electricity. Tenant shall pay to Landlord
monthly an amount reasonably estimated by Landlord to equal Tenant's Allocable
Electricity Costs for the electrical energy that Tenant requires for operation
of the lighting fixtures, appliances and equipment of Tenant in the Premises and
the heating and air conditioning equipment of Landlord servicing the Premises.
"Tenant's Allocable Electricity Costs" as used

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herein is initially estimated to be $1.25 per rsf, and shall be as determined in
accordance with Exhibit E attached hereto and made a part hereof. Landlord shall
from time to time furnish to Tenant a statement setting forth in reasonable
detail the particulars relating to Tenant's Allocable Electricity Costs for the
period to which such a statement relates. In the event the estimated payments
made by Tenant for said period shall be less than Tenant's Allocable Electricity
Costs for said period as set forth in said statement, Tenant shall promptly
remit to Landlord the difference. In the event the estimated payments made by
Tenant for said period exceed Tenant's Allocable Electricity Costs for said
period as set forth in said statement, such excess shall be refunded by
Landlord. Landlord shall not be liable in any way to Tenant for any failure or
defect in the supply or character of electrical energy furnished to the Premises
by reason of any requirement, act or omission of the public utility serving the
Building with electricity unless due to the act or omission of Landlord.
Tenant's use of electrical energy in the Premises shall not at any time exceed
the capacity of any of the electrical conductors and equipment in or otherwise
serving the Premises. In order to insure that such capacity is not exceeded and
to avert possible adverse affect upon the Building electrical services, Tenant
shall give notice to Landlord and obtain Landlord's prior written consent
whenever Tenant shall connect to the Building electrical distribution system any
major fixtures, appliances or equipment. Any additional feeders or risers to
supply Tenant's electrical requirements in addition to those originally
installed and all other equipment proper and necessary in connection with such
feeders or risers, shall be installed by Landlord upon Tenant's request, at the
sole cost and expense of Tenant, provided that such additional feeders and
risers are permissible under applicable laws and insurance regulations and the
installation of such feeders or risers will not cause permanent damage or injury
to the Building or cause or create a dangerous condition or unreasonably
interfere with other tenants of the Building. Tenant agrees that it will not
make any significant alteration or material addition to the electrical equipment
and/or appliances in the Premises without the prior written consent of Landlord
in each instance first obtained, which consent will not be unreasonably withheld
or delayed, and will promptly advise Landlord of any alteration or addition to
such electrical equipment and/or appliances. Except to the extent included in
the initial Landlord's Work, Tenant, at Tenant's expense, shall purchase,
install and replace all light fixtures, bulbs, tubes, lamps, lenses, globes,
ballasts and switches used in the Premises. Notwithstanding the foregoing,
Landlord, at its election, may install at Landlord's cost and expense a separate
meter for Tenant's electric usage in which event Tenant shall thereafter obtain
and pay for its electricity directly from the electric utility servicing the
Building.

     13.2 Should Tenant require any additional work or service, as described
above, including services furnished outside ordinary business hours specified
above, Landlord may, on terms to be agreed, upon reasonable advance notice by
Tenant, furnish such additional service and Tenant agrees to pay Landlord such
commercially reasonable charges as may be agreed upon, including any tax imposed
thereon, but in no event at a charge less than Landlord's actual cost plus
overhead for such additional service and, where appropriate, a reasonable
allowance for depreciation of any systems being used to provide such service.
The current charge for after-hours HVAC service, which is subject to change at
any time to reflect actual increases in cost to Landlord of providing such
after-hours HVAC service, is specified on the Reference Pages.

     13.3 Wherever heat-generating machines or equipment are used by Tenant in
the Premises which affect the temperature otherwise maintained by the air
conditioning system or Tenant allows occupancy of the Premises by more persons
than the heating and air conditioning system is designed to accommodate, in
either event whether with or without Landlord's approval, Landlord reserves the
right to consult with Tenant regarding the need to install supplementary heating
and/or air conditioning units in or for the benefit of the Premises. If Landlord
and Tenant agree that such additional units are required for the Premises, then
Landlord shall install such additional units and the cost thereof, including the
cost of installation and the cost of operations and maintenance, shall be paid
by Tenant to Landlord within fifteen (15) days of Landlord's demand, such demand
to include copies of the invoices showing the costs of purchasing and installing
said additional units.

     13.4 Tenant will not, without the written consent of Landlord, use any
apparatus or device in the Premises, including but not limited to, electronic
data processing machines and machines using current in excess of 2000 watts
and/or 30 amps or 220 volts, which will in any way increase the amount of
electricity or water usually furnished or supplied for use of the Premises for
normal office use, nor connect with electric current, except through existing
electrical outlets in the Premises, or water pipes, any apparatus or device for
the purposes of using electrical current or water. If Tenant shall require water
or electric current in excess of that usually furnished or supplied for use of
the Premises as normal office use, Tenant shall procure the prior written
consent of Landlord for the use

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<PAGE>

thereof, which Landlord may refuse, and if Landlord does consent, Landlord may
cause a water meter or electric current meter to be installed so as to measure
the amount of such excess water and electric current. The cost of any such
meters shall be paid for by Tenant. Tenant agrees to pay to Landlord within
fifteen (15) days of Landlord's demand, the cost of all such excess water and
electric current consumed (as shown by said meters, if any, or, if none, as
reasonably estimated by Landlord) at the rates charged for such services by the
local public utility or agency, as the case may be, furnishing the same, plus
any additional expense incurred in keeping account of the water and electric
current so consumed.

     13.5 Tenant will not, without the written consent of Landlord, contract
with a utility provider to service the Premises with any utility, including, but
not limited to, telecommunications, electricity, water, sewer or gas, which is
not previously providing such service to other tenants in the Building. Subject
to Landlord's reasonable rules and regulations and the provisions of Articles 6
and 26, Tenant shall be entitled to the use of wiring ("Communications Wiring")
from the existing telecommunications nexus in the Building to the Premises,
sufficient for normal general office use of the Premises. Tenant shall not
install any additional Communications Wiring, nor remove any Communications
Wiring, without in each instance obtaining the prior written consent of
Landlord, which consent may be withheld in Landlord's sole and absolute
discretion. Landlord's shall in no event be liable for disruption in any service
obtained by Tenant pursuant to this paragraph.

14. HOLDING OVER. Tenant shall pay Landlord for each day Tenant retains
possession of the Premises or part of them after termination of this Lease by
lapse of time or otherwise at the rate ("Holdover Rate") which shall be One
Hundred Fifty Percent (150%) of the greater of the amount of the Annual Rent for
the last period prior to the date of such termination plus all Rent Adjustments
under Article 4, prorated on a daily basis, and also pay all damages sustained
by Landlord by reason of such retention. If Landlord gives notice to Tenant of
Landlord's election to such effect, such holding over shall constitute renewal
of this Lease for a period from month to month or one (1) year, whichever shall
be specified in such notice, in either case at the Holdover Rate, but if the
Landlord does not so elect, no such renewal shall result notwithstanding
acceptance by Landlord of any sums due hereunder after such termination; and
instead, a tenancy at sufferance at the Holdover Rate shall be deemed to have
been created. In any event, no provision of this Article 14 shall be deemed to
waive Landlord's right of reentry or any other right under this Lease or at law.

15. SUBORDINATION. Without the necessity of any additional document being
executed by Tenant for the purpose of effecting a subordination, this Lease
shall be subject and subordinate at all times to ground or underlying leases and
to the lien of any mortgages or deeds of trust now or hereafter placed on,
against or affecting the Building, Landlord's interest or estate in the
Building, or any ground or underlying lease; provided, however, that if the
lessor, mortgagee, trustee, or holder of any such mortgage or deed of trust
elects to have Tenant's interest in this Lease be superior to any such
instrument, then, by notice to Tenant, this Lease shall be deemed superior,
whether this Lease was executed before or after said instrument. Notwithstanding
the foregoing, Tenant covenants and agrees to execute and deliver within ten
(10) days of Landlord's request such further instruments evidencing such
subordination or superiority of this Lease as may be required by Landlord.
Currently, there is no mortgage encumbering the property upon which the Building
is situated. As to any future mortgagee, Landlord shall request, and use
commercially reasonable efforts to obtain a reasonable non-disturbance letter
from any future mortgagees in such mortgagee's standard form, but the failure to
obtain such non-disturbance letter, despite such efforts, shall not be a breach
of this Lease.

16. RULES AND REGULATIONS. Tenant shall faithfully observe and comply with all
the rules and regulations as set forth in Exhibit D to this Lease and all
reasonable and non-discriminatory modifications of and additions to them from
time to time put into effect by Landlord. Landlord shall apply and enforce its
Rules and Regulations consistently for all tenants and occupants of the
Building, but shall not otherwise be responsible to Tenant for the
non-performance by any other tenant or occupant of the Building of any such
rules and regulations.

17. REENTRY BY LANDLORD.

     17.1 Subject to Section 17.2 hereof, Landlord reserves and shall at all
times have the right to re-enter the Premises to inspect the same, to supply
janitor service and any other service to be provided by Landlord to Tenant under
this Lease, to show said Premises to prospective purchasers, mortgagees or
tenants, and to alter,

                                       13

<PAGE>

improve or repair the Premises and any portion of the Building, without
abatement of rent, and may for that purpose erect, use and maintain scaffolding,
pipes, conduits and other necessary structures and open any wall, ceiling or
floor in and through the Building and Premises where reasonably required by the
character of the work to be performed, provided (a) Landlord shall endeavor to
provide Tenant, when reasonably possible, with at least forty-eight (48) hours
advance notice prior to any entrance into the Premises, except in the event of
emergency, when Landlord shall be required only to give such advance notice as
is reasonably practicable under the circumstances; (b) Landlord's work in the
Premises shall not block or materially impair entrance to the Premises; and (c)
any non-emergency entry into or work within the Premises shall be done at a time
and in such manner as minimizes any adverse impact on Tenant's use and enjoyment
of the Premises. Landlord shall have the right at any time to change the
arrangement and/or locations of entrances, or passageways, doors and doorways,
and corridors, windows, elevators, stairs, toilets or other public parts of the
Building and to change the name, number or designation by which the Building is
commonly known. In the event that Landlord damages any portion of any wall or
wall covering, ceiling, or floor or floor covering within the Premises, Landlord
shall repair or replace the damaged portion to match the original as nearly as
commercially reasonable but shall not be required to repair or replace more than
the portion actually damaged. Tenant hereby waives any claim for damages for any
injury or inconvenience to or interference with Tenant's business, any loss of
occupancy or quiet enjoyment of the Premises, and any other loss occasioned by
any action of Landlord authorized by this Article 17.

     17.2 For each of the aforesaid purposes, Landlord shall at all times have
and retain a key with which to unlock all of the doors in the Premises,
excluding Tenant's vaults and safes or special security areas (designated in
advance), and Landlord shall have the right to use any and all means which
Landlord may deem proper to open said doors in an emergency to obtain entry to
any portion of the Premises. As to any portion to which access cannot be had by
means of a key or keys in Landlord's possession, Landlord is authorized to gain
access by such means as Landlord shall elect and the cost of repairing any
damage occurring in doing so shall be borne by Tenant and paid to Landlord
within five (5) days of Landlord's demand. Except in the event of an emergency,
Landlord shall not enter into or perform any work or repairs in Tenant's data
center, except with Tenant's prior approval, which approval shall not be
unreasonably withheld. Landlord further covenants that Landlord shall not
install or maintain any pipe, drain or other plumbing conduit through or above
Tenant's data center as originally located as part of Landlord's Work.

18. DEFAULT.

     18.1 Except as otherwise provided in Article 20, the following events shall
be deemed to be Events of Default under this Lease:

          18.1.1 Tenant shall fail to pay when due any sum of money becoming due
to be paid to Landlord under this Lease, whether such sum be any installment of
the rent reserved by this Lease, any other amount treated as additional rent
under this Lease, or any other payment or reimbursement to Landlord required by
this Lease, whether or not treated as additional rent under this Lease, and such
failure shall continue for a period of five (5) days after written notice that
such payment was not made when due.

          18.1.2 Tenant shall fail to comply with any term, provision or
covenant of this Lease which is not provided for in another Section of this
Article and shall not cure such failure within twenty (20) days (forthwith, if
the failure involves a hazardous condition) after written notice of such failure
to Tenant provided, however, that such failure shall not be an event of default
if such failure could not reasonably be cured during such twenty (20) day
period, Tenant has commenced the cure within such twenty (20) day period and
thereafter is diligently pursuing such cure to completion, but the total
aggregate cure period shall not exceed one hundred twenty (120) days.

          18.1.3 Tenant shall fail to vacate the Premises immediately upon
termination of this Lease, by lapse of time or otherwise, or upon termination of
Tenant's right to possession only.

          18.1.4 Tenant shall become insolvent, admit in writing its inability
to pay its debts generally as they become due, file a petition in bankruptcy or
a petition to take advantage of any insolvency statute, make an assignment for
the benefit of creditors, make a transfer in fraud of creditors, apply for or
consent to the appointment of a receiver of itself or of the whole or any
substantial part of its property, or file a petition or answer seeking

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<PAGE>

reorganization or arrangement under the federal bankruptcy laws, as now in
effect or hereafter amended, or any other applicable law or statute of the
United States or any state thereof.

          18.1.5 A court of competent jurisdiction shall enter an order,
judgment or decree adjudicating Tenant bankrupt, or appointing a receiver of
Tenant, or of the whole or any substantial part of its property, without the
consent of Tenant, or approving a petition filed against Tenant seeking
reorganization or arrangement of Tenant under the bankruptcy laws of the United
States, as now in effect or hereafter amended, or any state thereof, and such
order, judgment or decree shall not be vacated or set aside or stayed within
sixty (60) days from the date of entry thereof.

19. REMEDIES.

     19.1 Except as otherwise provided in Article 20, upon the occurrence of any
of the Events of Default described or referred to in Article 18, Landlord shall
have the option to pursue any one or more of the following remedies without any
notice or demand whatsoever, concurrently or consecutively and not
alternatively:

          19.1.1 Landlord may, at its election, terminate this Lease or
terminate Tenant's right to possession only, without terminating the Lease.

          19.1.2 Upon any termination of this Lease, whether by lapse of time or
otherwise, or upon any termination of Tenant's right to possession without
termination of the Lease, Tenant shall surrender possession and vacate the
Premises immediately, and deliver possession thereof to Landlord, and Tenant
hereby grants to Landlord full and free license to enter into and upon the
Premises in such event and to repossess Landlord of the Premises as of
Landlord's former estate and to expel or remove Tenant and any others who may be
occupying or be within the Premises and to remove Tenant's signs and other
evidence of tenancy and all other property of Tenant therefrom without being
deemed in any manner guilty of trespass, eviction or forcible entry or detainer,
and without incurring any liability for any damage resulting therefrom, Tenant
waiving any right to claim damages for such re-entry and expulsion, and without
relinquishing Landlord's right to rent or any other right given to Landlord
under this Lease or by operation of law.

          19.1.3 Upon any termination of this Lease, whether by lapse of time or
otherwise, Landlord shall be entitled to recover as damages, all rent, including
any amounts treated as additional rent under this Lease, and other sums due and
payable by Tenant on the date of termination, plus as liquidated damages and not
as a penalty, an amount equal to the sum of: (a) an amount equal to the then
present value of the rent reserved in this Lease for the residue of the stated
Term of this Lease including any amounts treated as additional rent under this
Lease and all other sums provided in this Lease to be paid by Tenant, minus the
fair rental value of the Premises for such residue; (b) the value of the time
and expense necessary to obtain a replacement tenant or tenants, and the
estimated expenses described in Section 19.1.4 relating to recovery of the
Premises, preparation for reletting and for reletting itself; and (c) the cost
of performing any other covenants which would have otherwise been performed by
Tenant.

          19.1.4 Upon any termination of Tenant's right to possession only
without termination of the Lease:

               19.1.4.1 Neither such termination of Tenant's right to possession
nor Landlord's taking and holding possession thereof as provided in Section
19.1.2 shall terminate the Lease or release Tenant, in whole or in part, from
any obligation, including Tenant's obligation to pay the rent, including any
amounts treated as additional rent, under this Lease for the full Term, and if
Landlord so elects Tenant shall continue to pay to Landlord the entire amount of
the rent as and when it becomes due, including any amounts treated as additional
rent under this Lease, for the remainder of the Term plus any other sums
provided in this Lease to be paid by Tenant for the remainder of the Term.

               19.1.4.2 Landlord shall use commercially reasonable efforts to
relet the Premises or portions thereof. Landlord and Tenant agree that
nevertheless Landlord shall at most be required to use only the same efforts
Landlord then uses to lease premises in the Building generally and that in any
case that Landlord shall

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<PAGE>

not be required to give any preference or priority to the showing or leasing of
the Premises or portions thereof over any other space that Landlord may be
leasing or have available and may place a suitable prospective tenant in any
such other space regardless of when such other space becomes available and that
Landlord shall have the right to relet the Premises for a greater or lesser term
than that remaining under this Lease, the right to relet only a portion of the
Premises, or a portion of the Premises or the entire Premises as a part of a
larger area, and the right to change the character or use of the Premises. In
connection with or in preparation for any reletting, Landlord may, but shall not
be required to, make repairs, alterations and additions in or to the Premises
and redecorate the same to the extent Landlord deems necessary or desirable, and
Tenant shall pay the cost thereof, together with Landlord's expenses of
reletting, including, without limitation, any commission incurred by Landlord,
within twenty (20) days after Landlord's demand. Landlord shall not be required
to observe any instruction given by Tenant about any reletting or accept any
tenant offered by Tenant unless such offered tenant has a credit-worthiness
reasonably acceptable to Landlord and leases all or substantially all of the
Premises upon terms and conditions including a rate of rent (after giving effect
to all expenditures by Landlord for tenant improvements, broker's commissions
and other leasing costs) all no less favorable to Landlord than as called for in
this Lease, nor shall Landlord be required to make or permit any assignment or
sublease for more than the current term or which Landlord would not be required
to permit under the provisions of Article 9.

               19.1.4.3 Until such time as Landlord shall elect to terminate the
Lease and shall thereupon be entitled to recover the amounts specified in such
case in Section 19.1.3, Tenant shall pay to Landlord upon demand the full amount
of all rent, including any amounts treated as additional rent under this Lease
and other sums reserved in this Lease for the remaining Term, together with the
costs of repairs, alterations, additions, redecorating and Landlord's expenses
of reletting and the collection of the rent accruing therefrom (including
reasonable attorney's fees and broker's commissions), as the same shall then be
due or become due from time to time, less only such consideration as Landlord
may have received from any reletting of the Premises; and Tenant agrees that
Landlord may file suits from time to time to recover any sums falling due under
this Article 19 as they become due. Any proceeds of reletting by Landlord in
excess of the amount then owed by Tenant to Landlord from time to time shall be
credited against Tenant's future obligations under this Lease but shall not
otherwise be refunded to Tenant or inure to Tenant's benefit.

     19.2 Upon the occurrence of an Event of Default, Landlord may (but shall
not be obligated to) cure such default at Tenant's sole expense. Without
limiting the generality of the foregoing, Landlord may, at Landlord's option,
enter into and upon the Premises if Landlord determines in its sole discretion
that Tenant is not acting within a commercially reasonable time to maintain,
repair or replace anything for which Tenant is responsible under this Lease or
to otherwise effect compliance with its obligations under this Lease and correct
the same, without being deemed in any manner guilty of trespass, eviction or
forcible entry and detainer and without incurring any liability for any damage
or interruption of Tenant's business resulting therefrom, except for Landlord's
gross negligence or willful misconduct, and Tenant agrees to reimburse Landlord
within five (5) days of Landlord's demand as additional rent, for any expenses
which Landlord may incur in thus effecting compliance with Tenant's obligations
under this Lease, plus interest from the date of expenditure by Landlord at the
Wall Street Journal prime rate; provided Landlord shall comply with the notice
and other requirements of re-entry set forth in Section 17 of this Lease.

     19.3 Tenant understands and agrees that in entering into this Lease,
Landlord is relying upon receipt of all the Annual and Monthly Installments of
Rent to become due with respect to all the Premises originally leased hereunder
over the full Initial Term of this Lease for amortization, including interest at
the Amortization Rate. For purposes hereof, the "Concession Amount" shall be
defined as the aggregate of all amounts forgone or expended by Landlord as free
rent under the lease, under Exhibit B hereof for construction allowances
(excluding therefrom any amounts expended by Landlord for Landlord's Work, as
defined in Exhibit B), and for brokers' commissions payable by reason of this
Lease. Accordingly, Tenant agrees that if this Lease or Tenant's right to
possession of the Premises leased hereunder shall be terminated as of any date
("Default Termination Date") prior to the expiration of the full Initial Term
hereof by reason of a default of Tenant, there shall be due and owing to
Landlord as of the day prior to the Default Termination Date, as rent in
addition to all other amounts owed by Tenant as of such Date, the amount
("Unamortized Amount") of the Concession Amount determined as set forth below;
provided, however, that in the event that such amounts are recovered by Landlord
pursuant to any other provision of this Article 19, Landlord agrees that it
shall not attempt to recover such amounts pursuant to this Paragraph 19.3. For
the purposes

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<PAGE>

hereof, the Unamortized Amount shall be determined in the same manner as the
remaining principal balance of a mortgage with interest at the Amortization Rate
payable in level payments over the same length of time as from the effectuation
of the Concession concerned to the end of the full Initial Term of this Lease
would be determined. The foregoing provisions shall also apply to and upon any
reduction of space in the Premises, as though such reduction were a termination
for Tenant's default, except that (i) the Unamortized Amount shall be reduced by
any amounts paid by Tenant to Landlord to effectuate such reduction and (ii) the
manner of application shall be that the Unamortized Amount shall first be
determined as though for a full termination as of the Effective Date of the
elimination of the portion, but then the amount so determined shall be
multiplied by the fraction of which the numerator is the rentable square footage
of the eliminated portion and the denominator is the rentable square footage of
the Premises originally leased hereunder; and the amount thus obtained shall be
the Unamortized Amount.

     19.4 If, on account of any breach or default by Tenant in Tenant's
obligations under the terms and conditions of this Lease, it shall become
necessary or appropriate for Landlord to employ or consult with an attorney or
collection agency to enforce or defend any of Landlord's rights or remedies
arising under this Lease or to collect any sums due from Tenant, Tenant agrees
to pay all costs and fees so incurred by Landlord, including, without
limitation, reasonable attorneys' fees and costs. TENANT EXPRESSLY WAIVES ANY
RIGHT TO TRIAL BY JURY.

     19.5 Pursuit of any of the foregoing remedies shall not preclude pursuit of
any of the other remedies provided in this Lease or any other remedies provided
by law (all such remedies being cumulative), nor shall pursuit of any remedy
provided in this Lease constitute a forfeiture or waiver of any rent due to
Landlord under this Lease or of any damages accruing to Landlord by reason of
the violation of any of the terms, provisions and covenants contained in this
Lease.

     19.6 No act or thing done by Landlord or its agents during the Term shall
be deemed a termination of this Lease or an acceptance of the surrender of the
Premises, and no agreement to terminate this Lease or accept a surrender of said
Premises shall be valid, unless in writing signed by Landlord. No waiver by
Landlord of any violation or breach of any of the terms, provisions and
covenants contained in this Lease shall be deemed or construed to constitute a
waiver of any other violation or breach of any of the terms, provisions and
covenants contained in this Lease. Landlord's acceptance of the payment of
rental or other payments after the occurrence of an Event of Default shall not
be construed as a waiver of such Default, unless Landlord so notifies Tenant in
writing. Forbearance by Landlord in enforcing one or more of the remedies
provided in this Lease upon an Event of Default shall not be deemed or construed
to constitute a waiver of such Default or of Landlord's right to enforce any
such remedies with respect to such Default or any subsequent Default.

     19.7 Intentionally deleted.

     19.8 Any and all property which may be removed from the Premises by
Landlord pursuant to the authority of this Lease or of law, to which Tenant is
or may be entitled, may be handled, removed and/or stored, as the case may be,
by or at the direction of Landlord but at the risk, cost and expense of Tenant,
and Landlord shall in no event be responsible for the value, preservation or
safekeeping thereof. Tenant shall pay to Landlord, upon demand, any and all
expenses incurred in such removal and all storage charges against such property
so long as the same shall be in Landlord's possession or under Landlord's
control. Any such property of Tenant not retaken by Tenant from storage within
thirty (30) days after removal from the Premises shall, at Landlord's option, be
deemed conveyed by Tenant to Landlord under this Lease as by a bill of sale
without further payment or credit by Landlord to Tenant.

     19.9 Intentionally deleted.

20. TENANT'S BANKRUPTCY OR INSOLVENCY.

     20.1 If at any time and for so long as Tenant shall be subjected to the
provisions of the United States Bankruptcy Code or other law of the United
States or any state thereof for the protection of debtors as in effect at such
time (each a "Debtor's Law"):

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          20.1.1 Tenant, Tenant as debtor-in-possession, and any trustee or
receiver of Tenant's assets (each a "Tenant's Representative") shall have no
greater right to assume or assign this Lease or any interest in this Lease, or
to sublease any of the Premises than accorded to Tenant in Article 9, except to
the extent Landlord shall be required to permit such assumption, assignment or
sublease by the provisions of such Debtor's Law. Without limitation of the
generality of the foregoing, any right of any Tenant's Representative to assume
or assign this Lease or to sublease any of the Premises shall be subject to the
conditions that:

               20.1.1.1 Such Debtor's Law shall provide to Tenant's
Representative a right of assumption of this Lease which Tenant's Representative
shall have timely exercised and Tenant's Representative shall have fully cured
any default of Tenant under this Lease.

               20.1.1.2 Tenant's Representative or the proposed assignee, as the
case shall be, shall have deposited with Landlord as security for the timely
payment of rent an amount equal to the larger of: (a) three (3) months' rent and
other monetary charges accruing under this Lease; and (b) any sum specified in
Article 4.1; and shall have provided Landlord with adequate other assurance of
the future performance of the obligations of the Tenant under this Lease.
Without limitation, such assurances shall include, at least, in the case of
assumption of this Lease, demonstration to the satisfaction of the Landlord that
Tenant's Representative has and will continue to have sufficient unencumbered
assets after the payment of all secured obligations and administrative expenses
to assure Landlord that Tenant's Representative will have sufficient funds to
fulfill the obligations of Tenant under this Lease; and, in the case of
assignment, submission of current financial statements of the proposed assignee,
audited by an independent certified public accountant reasonably acceptable to
Landlord and showing a net worth and working capital in amounts determined by
Landlord to be sufficient to assure the future performance by such assignee of
all of the Tenant's obligations under this Lease.

               20.1.1.3 The assumption or any contemplated assignment of this
Lease or subleasing any part of the Premises, as shall be the case, will not
breach any provision in any other lease, mortgage, financing agreement or other
agreement by which Landlord is bound.

               20.1.1.4 Landlord shall have, or would have had absent the
Debtor's Law, no right under Article 9 to refuse consent to the proposed
assignment or sublease by reason of the identity or nature of the proposed
assignee or sublessee or the proposed use of the Premises concerned.

21. QUIET ENJOYMENT. Landlord represents and warrants that it has full right and
authority to enter into this Lease and that Tenant, while paying the rental and
performing its other covenants and agreements contained in this Lease, shall
peaceably and quietly have, hold and enjoy the Premises for the Term without
hindrance or molestation from Landlord subject to the terms and provisions of
this Lease. Landlord shall not be liable for any interference or disturbance by
other tenants or third persons, nor shall Tenant be released from any of the
obligations of this Lease because of such interference or disturbance.

22. CASUALTY

     22.1 In the event the Premises or the Building are damaged by fire or other
cause and in Landlord's reasonable estimation such damage can be materially
restored within one hundred eighty (180) days, Landlord shall within ten (10)
business days give Tenant written notice of Landlord's reasonable estimation of
the date by which material restoration can be made (the "Estimated Restoration
Date"), and Landlord forthwith shall repair the same and this Lease shall remain
in full force and effect, except that Tenant shall be entitled to a
proportionate abatement in rent from the date of such damage. Such abatement of
rent shall be made pro rata in accordance with the extent to which the damage
and the making of such repairs shall interfere with the use and occupancy by
Tenant of the Premises from time to time. For purposes of this Lease, the
Building or Premises shall be deemed "materially restored" if they are in such
condition as would not prevent or materially interfere with Tenant's use of the
Premises.

     22.2 If such repairs cannot, in Landlord's reasonable estimation, be made
within one hundred eighty (180) days, Landlord and Tenant shall each have the
option of giving the other, at any time within sixty (60) days after such
damage, notice terminating this Lease as of the date of such damage. In the
event of the giving of such notice, this Lease shall expire and all interest of
the Tenant in the Premises shall terminate as of the date of such

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damage as if such date had been originally fixed in this Lease for the
expiration of the Term. In the event that neither Landlord nor Tenant exercises
its option to terminate this Lease, then Landlord shall repair or restore such
damage, this Lease continuing in full force and effect, and the rent hereunder
shall be proportionately abated as provided in Section 22.1.

     22.3 Landlord shall not be required to repair or replace any damage or loss
by or from fire or other cause to any panelings, decorations, partitions,
additions, railings, ceilings, floor coverings, office fixtures or any other
property or improvements installed on the Premises by, or belonging to, Tenant,
except for any such fixtures or improvements which were included in Landlord's
Work. Any insurance which may be carried by Landlord or Tenant against loss or
damage to the Building or Premises shall be for the sole benefit of the party
carrying such insurance and under its sole control.

     22.4 In the event that Landlord should fail to complete such repairs and
material restoration within sixty (60) days after the Estimated Restoration
Date, Tenant may at its option and as its sole remedy terminate this Lease by
delivering written notice to Landlord, within fifteen (15) days after the
expiration of said period of time, whereupon the Lease shall end as of the
Estimated Restoration Date, of or such later date fixed in such notice, as if
the Estimated Restoration Date (or later date specified in Tenant's notice) was
the date originally fixed in this Lease for the expiration of the Term;
provided, however, that if construction is delayed because of changes, deletions
or additions in construction requested by Tenant, strikes, lockouts, casualties,
Acts of God, war, material or labor shortages, government regulation or control
or other causes beyond the reasonable control of Landlord, the period for
restoration, repair or rebuilding shall be extended for the amount of time
Landlord is so delayed.

     22.5 Notwithstanding anything to the contrary contained in this Article:
(a) Landlord shall not have any obligation whatsoever to repair, reconstruct, or
restore the Premises when the damages resulting from any casualty covered by the
provisions of this Article 22 occur during the last twelve (12) months of the
Term or any extension thereof, but if Landlord determines not to repair such
damages Landlord shall notify Tenant and if such damages shall render any
material portion of the Premises untenantable Tenant shall have the right to
terminate this Lease by notice to Landlord within fifteen (15) days after
receipt of Landlord's notice; and (b) in the event the holder of any
indebtedness secured by a mortgage or deed of trust covering the Premises or
Building requires that any insurance proceeds be applied to such indebtedness,
then Landlord shall have the right to terminate this Lease by delivering written
notice of termination to Tenant within fifteen (15) days after such requirement
is made by any such holder, whereupon this Lease shall end on the date of such
damage as if the date of such damage were the date originally fixed in this
Lease for the expiration of the Term.

     22.6 In the event of any damage or destruction to the Building or Premises
by any peril covered by the provisions of this Article 22, it shall be Tenant's
responsibility to properly secure the Premises and upon notice from Landlord to
remove forthwith, at its sole cost and expense, such portion of all of the
property belonging to Tenant or its licensees from such portion or all of the
Building or Premises as Landlord shall request.

23. EMINENT DOMAIN. If all or any substantial part of the Premises shall be
taken or appropriated by any public or quasi-public authority under the power of
eminent domain, or conveyance in lieu of such appropriation, either party to
this Lease shall have the right, at its option, of giving the other, at any time
within thirty (30) days after such taking, notice terminating this Lease, except
that Tenant may only terminate this Lease by reason of taking or appropriation,
if such taking or appropriation shall be so substantial as to materially
interfere with Tenant's use and occupancy of the Premises. If neither party to
this Lease shall so elect to terminate this Lease, the rental thereafter to be
paid shall be adjusted on a fair and equitable basis under the circumstances. In
addition to the rights of Landlord above, if any substantial part of the
Building shall be taken or appropriated by any public or quasi-public authority
under the power of eminent domain or conveyance in lieu thereof, and regardless
of whether the Premises or any part thereof are so taken or appropriated,
Landlord shall have the right, at its sole option, to terminate this Lease.
Landlord shall be entitled to any and all income, rent, award, or any interest
whatsoever in or upon any such sum, which may be paid or made in connection with
any such public or quasi-public use or purpose, and Tenant hereby assigns to
Landlord any interest it may have in or claim to all or any part of such sums,
other than any separate award which may be made with respect to Tenant's trade
fixtures and moving expenses; Tenant shall make no claim for the value of any
unexpired Term.

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24. SALE BY LANDLORD. In event of a sale or conveyance by Landlord of the
Building, the same shall operate to release Landlord from any future liability
upon any of the covenants or conditions, expressed or implied, contained in this
Lease in favor of Tenant, and in such event Tenant agrees to look solely to the
responsibility of the successor in interest of Landlord in and to this Lease.
Except as set forth in this Article 24, this Lease shall not be affected by any
such sale and Tenant agrees to attorn to the purchaser or assignee. If any
security has been given by Tenant to secure the faithful performance of any of
the covenants of this Lease, Landlord may transfer or deliver said security, as
such, to Landlord's successor in interest and thereupon Landlord shall be
discharged from any further liability with regard to said security.

25. ESTOPPEL CERTIFICATES. Within ten (10) days following any written request
which Landlord may make from time to time, Tenant shall execute and deliver to
Landlord or mortgagee or prospective mortgagee a sworn statement certifying: (a)
the date of commencement of this Lease; (b) the fact that this Lease is
unmodified and in full force and effect (or, if there have been modifications to
this Lease, that this lease is in full force and effect, as modified, and
stating the date and nature of such modifications); (c) the date to which the
rent and other sums payable under this Lease have been paid; (d) the fact that
there are no current defaults under this Lease by either Landlord or Tenant
except as specified in Tenant's statement; and (e) such other matters as may be
requested by Landlord. Landlord and Tenant intend that any statement delivered
pursuant to this Article 25 may be relied upon by any mortgagee, beneficiary or
purchaser. Tenant irrevocably agrees that if Tenant fails to execute and deliver
such certificate within such ten (10) day period Landlord or Landlord's
beneficiary or agent may execute and deliver such certificate on Tenant's
behalf, and that such certificate shall be fully binding on Tenant.

26. SURRENDER OF PREMISES.

     26.1 Tenant shall arrange to meet Landlord for two (2) joint inspections of
the Premises, the first to occur at least thirty (30) days (but no more than
sixty (60) days) before the last day of the Term, and the second to occur not
later than forty-eight (48) hours after Tenant has vacated the Premises. In the
event of Tenant's failure to arrange such joint inspections and/or participate
in either such inspection, Landlord's inspection at or after Tenant's vacating
the Premises shall be conclusively deemed correct for purposes of determining
Tenant's responsibility for repairs and restoration.

     26.2 All alterations, additions, and improvements in, on, or to the
Premises made or installed by or for Tenant,(collectively, "Alterations"), shall
be and remain the property of Tenant during the Term. Upon the expiration or
sooner termination of the Term, all Alterations shall become a part of the
realty and shall belong to Landlord without compensation, and title shall pass
to Landlord under this Lease as by a bill of sale. At the end of the Term or any
renewal of the Term or other sooner termination of this Lease, Tenant will
peaceably deliver up to Landlord possession of the Premises, together with all
Alterations by whomsoever made, in the same conditions received or first
installed, broom clean and free of all debris, excepting only ordinary wear and
tear and damage by fire or other casualty. Notwithstanding the foregoing, if
Landlord elects by notice given to Tenant at least ten (10) days prior to
expiration of the Term, Tenant shall, at Tenant's sole cost, remove any
Alterations so designated by Landlord's notice, and repair any damage caused by
such removal; provided, however, that if such Alterations required Landlord's
approval, Tenant shall not be required to remove such Alteration at the end of
the Term or earlier termination of this Lease, provided that Tenant shall have
requested at the time of the request for approval of such Alterations a
determination as to whether removal of such Alterations would be required and
Landlord advises Tenant that removal of such Alterations would not be required
at the expiration or earlier termination of this Lease. Tenant must, at Tenant's
sole cost, remove upon termination of this Lease, any and all of Tenant's
furniture, furnishings, equipment, movable partitions of less than full height
from floor to ceiling and other trade fixtures and personal property, as well as
all data/telecommunications cabling and wiring installed by or on behalf of
Tenant, whether inside walls, under any raised floor or above any ceiling
(collectively, "Personalty"). Personalty not so removed shall be deemed
abandoned by the Tenant and title to the same shall thereupon pass to Landlord
under this Lease as by a bill of sale, but Tenant shall remain responsible for
the cost of removal and disposal of such Personalty, as well as any damage
caused by such removal. In lieu of requiring Tenant to remove Alterations and
Personalty and repair the Premises as aforesaid, Landlord may, by written notice
to Tenant delivered at least thirty (30) days before the Termination Date,
require Tenant to pay to Landlord, as additional rent hereunder, the cost of
such removal and repair in an amount reasonably estimated by Landlord.

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     26.3 All obligations of Tenant under this Lease not fully performed as of
the expiration or earlier termination of the Term shall survive the expiration
or earlier termination of the Term. Any otherwise unused Security Deposit shall
be credited against the amount payable by Tenant under this Lease.

27. NOTICES. Any notice or document required or permitted to be delivered under
this Lease shall be addressed to the intended recipient, by fully prepaid
registered or certified United States Mail return receipt requested, or by
reputable independent contract delivery service furnishing a written record of
attempted or actual delivery, and shall be deemed to be delivered when tendered
for delivery to the addressee at its address set forth on the Reference Pages to
the attention of Accounts Payable with copy to the General Counsel, or at such
other address as it has then last specified by written notice delivered in
accordance with this Article 27, whether or not actually accepted or received by
the addressee. Any such notice or document may also be personally delivered if a
receipt is signed by and received from, the individual, if any, named in
Tenant's Notice Address. Any notice to Tenant shall be sent with a copy to
Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., One Financial Center,
Boston, Massachusetts 02111, Attention: Jonathan M. Cosco, Esq.

28. TAXES PAYABLE BY TENANT. In addition to rent and other charges to be paid by
Tenant under this Lease, Tenant shall reimburse to Landlord, upon demand, any
and all taxes payable by Landlord (other than net income taxes) whether or not
now customary or within the contemplation of the parties to this Lease: (a)
upon, allocable to, or measured by or on the gross or net rent payable under
this Lease, including without limitation any gross income tax or excise tax
levied by the State, any political subdivision thereof, or the Federal
Government with respect to the receipt of such rent; (b) upon or with respect to
the possession, leasing, operation, management, maintenance, alteration, repair,
use or occupancy of the Premises or any portion thereof, including any sales,
use or service tax imposed as a result thereof; (c) upon or measured by the
Tenant's gross receipts or payroll or the value of Tenant's equipment,
furniture, fixtures and other personal property of Tenant or leasehold
improvements, alterations or additions located in the Premises; or (d) upon this
transaction or any document to which Tenant is a party creating or transferring
any interest of Tenant in this Lease or the Premises. In addition to the
foregoing, Tenant agrees to pay, before delinquency, any and all taxes levied or
assessed against Tenant and which become payable during the term hereof upon
Tenant's equipment, furniture, fixtures and other personal property of Tenant
located in the Premises.

29. INTENTIONALLY DELETED.

30. DEFINED TERMS AND HEADINGS. The Article headings shown in this Lease are for
convenience of reference and shall in no way define, increase, limit or describe
the scope or intent of any provision of this Lease. Any indemnification or
insurance of Landlord shall apply to and inure to the benefit of all the
following "Landlord Entities", being Landlord, Landlord's investment manager,
and the trustees, boards of directors, officers, general partners,
beneficiaries, stockholders, employees and agents of each of them. Any option
granted to Landlord shall also include or be exercisable by Landlord's trustee,
beneficiary, agents and employees, as the case may be. In any case where this
Lease is signed by more than one person, the obligations under this Lease shall
be joint and several. The terms "Tenant" and "Landlord" or any pronoun used in
place thereof shall indicate and include the masculine or feminine, the singular
or plural number, individuals, firms or corporations, and their and each of
their respective successors, executors, administrators and permitted assigns,
according to the context hereof. The term "rentable area" shall mean the
rentable area of the Premises or the Building as calculated by the Landlord on
the basis of the plans and specifications of the Building including a
proportionate share of any common areas. Tenant hereby accepts and agrees to be
bound by the figures for the rentable space footage of the Premises and Tenant's
Proportionate Share shown on the Reference Pages; however, Landlord may adjust
either or both figures if there is manifest error, addition or subtraction to
the Building or any business park or complex of which the Building is a part,
remeasurement or other circumstance reasonably justifying adjustment. The term
"Building" refers to the structure in which the Premises are located and the
common areas (parking lots, sidewalks, landscaping, etc.) appurtenant thereto.
If the Building is part of a larger complex of structures, the term "Building"
may include the entire complex, where appropriate (such as shared Expenses,
Insurance Costs or Taxes) and subject to Landlord's reasonable discretion.

31. TENANT'S AUTHORITY. Each of the persons executing this Lease on behalf of
Tenant represents and warrants that Tenant has been and is qualified to do
business in the state in which the Building is located, that the

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entity has full right and authority to enter into this Lease, and that all
persons signing on behalf of the entity were authorized to do so by appropriate
actions. Tenant agrees to deliver to Landlord, simultaneously with the delivery
of this Lease, a corporate resolution, evidencing the due authorization of
Tenant to enter into this Lease. Each of the persons executing this Lease on
behalf of Landlord represents and warrants that Landlord has been and is
qualified to do business in the state in which the Building is located, that
Landlord has full right and authority to enter into this Lease, and that all
persons signing on behalf of Landlord were authorized to do so by appropriate
actions.

     Tenant hereby represents and warrants that neither Tenant, nor any persons
or entities holding any legal or beneficial interest whatsoever in Tenant, are
(i) the target of any sanctions program that is established by Executive Order
of the President or published by the Office of Foreign Assets Control, U.S.
Department of the Treasury ("OFAC"); (ii) designated by the President or OFAC
pursuant to the Trading with the Enemy Act, 50 U.S.C. App. Section 5, the
International Emergency Economic Powers Act, 50 U.S.C. Sections 1701-06, the
Patriot Act, Public Law 107-56, Executive Order 13224 (September 23, 2001) or
any Executive Order of the President issued pursuant to such statutes; or (iii)
named on the following list that is published by OFAC: "List of Specially
Designated Nationals and Blocked Persons." If the foregoing representation is
untrue at any time during the Term, an Event of Default will be deemed to have
occurred, without the necessity of notice to Tenant.

32. FINANCIAL STATEMENTS AND CREDIT REPORTS. At Landlord's request, but not more
than once in any twelve (12) month period, Tenant shall deliver to Landlord a
copy, certified by an officer of Tenant as being a true and correct copy, of
Tenant's most recent audited financial statement as filed with the United States
Securities and Exchange Commission. Tenant hereby authorizes Landlord to obtain
one or more credit reports on Tenant at any time, and shall execute such further
authorizations as Landlord may reasonably require in order to obtain a credit
report.

33. COMMISSIONS. Each of the parties represents and warrants to the other that
it has not dealt with any broker or finder in connection with this Lease, except
as described on the Reference Pages, which Brokers shall be compensated by the
Landlord per a separate agreement.

34. TIME AND APPLICABLE LAW. Time is of the essence of this Lease and all of its
provisions. This Lease shall in all respects be governed by the laws of the
state in which the Building is located.

35. SUCCESSORS AND ASSIGNS. Subject to the provisions of Article 9, the terms,
covenants and conditions contained in this Lease shall be binding upon and inure
to the benefit of the heirs, successors, executors, administrators and assigns
of the parties to this Lease.

36. ENTIRE AGREEMENT. This Lease, together with its exhibits, contains all
agreements of the parties to this Lease and supersedes any previous
negotiations. There have been no representations made by the Landlord or any of
its representatives or understandings made between the parties other than those
set forth in this Lease and its exhibits. This Lease may not be modified except
by a written instrument duly executed by the parties to this Lease.

37. EXAMINATION NOT OPTION. Submission of this Lease shall not be deemed to be a
reservation of the Premises. Landlord shall not be bound by this Lease until it
has received a copy of this Lease duly executed by Tenant and has delivered to
Tenant a copy of this Lease duly executed by Landlord. Notwithstanding anything
contained in this Lease to the contrary, Landlord may withhold delivery of
possession of the Premises from Tenant until such time as Tenant has paid to
Landlord any security deposit required by Article 4.1 and any sum owed pursuant
to this Lease.

38. RECORDATION. Tenant shall not record or register this Lease or a short form
memorandum hereof without the prior written consent of Landlord, and then shall
pay all charges and taxes incident such recording or registration.

39. PARKING.

     39.1 During the initial Term of this Lease, Tenant agrees to lease from
Landlord and Landlord agrees to lease to Tenant, the number and type of parking
passes as set forth on the Reference Page of this Lease. This right

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<PAGE>

to park in the Building's parking facilities (the "Parking Facility") shall be
on an unreserved, nonexclusive, first come, first served basis, for
passenger-size automobiles and is subject to the following terms and conditions:

          39.1.1 Tenant shall pay to Landlord, or Landlord's designated parking
operator, the Building's prevailing monthly parking charges, without deduction
or offset (except as provided in Section 39.1.3 hereof), on the first day of
each month during the Term of this Lease. The initial charges are specified on
the Reference Page. Landlord will notify Tenant upon not less than thirty (30)
days' notice of any increases in the monthly parking charges prior to billing
Tenant any increases. No deductions from the monthly charge shall be made for
days on which the Parking Facility is not used by Tenant.

          39.1.2 Tenant shall at all times abide by and shall cause each of
Tenant's employees, agents, customers, visitors, invitees, licensees,
contractors, assignees and subtenants (collectively, "Tenant's Parties") to
abide by any rules and regulations ("Rules") for use of the Parking Facility
that Landlord or Landlord's garage operator reasonably establishes from time to
time, and otherwise agrees to use the Parking Facility in a safe and lawful
manner. Landlord reserves the right to adopt, modify and enforce the Rules
governing the use of the Parking Facility from time to time including any
key-card, sticker or other identification or entrance system and hours of
operation. Landlord may refuse to permit any person who violates such Rules to
park in the Parking Facility, and any violation of the Rules shall subject the
car to removal from the Parking Facility.

          39.1.3 Unless specified to the contrary above, the parking spaces
hereunder shall be provided on a non-designated "first-come, first-served"
basis. Landlord reserves the right to assign specific spaces, and to reserve
spaces for visitors, small cars, disabled persons or for other tenants or
guests, and Tenant shall not park and shall not allow Tenant's Parties to park
in any such assigned or reserved spaces. Tenant may validate visitor parking by
such method as Landlord may approve, at the validation rate from time to time
generally applicable to visitor parking. Tenant acknowledges that the Parking
Facility may be closed entirely or in part in order to make repairs or perform
maintenance services, or to alter, modify, re-stripe or renovate the Parking
Facility, or if required by casualty, strike, condemnation, act of God,
governmental law or requirement or other reason beyond the operator's reasonable
control. If the Parking Facility or any portion thereof is closed and as a
result Tenant is unable to use the spaces therein for any period of time, then
Tenant's parking fees shall be ratably discounted, and if any such parking fees
have been paid in advance, Landlord shall refund such fees or appropriate
portion thereof upon written demand by Tenant.

          39.1.4 Tenant acknowledges that to the fullest extent permitted by
law, Landlord shall have no liability for any damage to property or other items
located in the parking areas of the Project (including without limitation, any
loss or damage to tenant's automobile or the contents thereof due to theft,
vandalism or accident), nor for any personal injuries or death arising out of
the use of the Parking Facility by Tenant or any Tenant's Parties, whether or
not such loss or damage results from Landlord's active negligence or negligent
omission. The limitation on Landlord's liability under the preceding sentence
shall not apply however to loss or damage arising directly from Landlord's
willful misconduct. Without limiting the foregoing, if Landlord arranges for the
parking areas to be operated by an independent contractor not affiliated with
Landlord, Tenant acknowledges that Landlord shall have no liability for claims
arising through acts or omissions of such independent contractor. Tenant and
Tenant's Parties each hereby voluntarily releases, discharges, waives and
relinquishes any and all actions or causes of action for personal injury or
property damage occurring to Tenant or any of Tenant's Parties arising as a
result of parking in the Parking Facility, or any activities incidental thereto,
wherever or however the same may occur, and further agrees that Tenant will not
prosecute any claim for personal injury or property damage against Landlord or
any of its officers, agents, servants or employees for any said causes of action
and in all events, Tenant agrees to look first to its insurance carrier and to
require that Tenant's Parties look first to their respective insurance carriers
for payment of any losses sustained in connection with any use of the Parking
Facility. Tenant hereby waives on behalf of its insurance carriers all rights of
subrogation against Landlord or Landlord's agents.

          39.1.5 Tenant's right to park as described in this Article and this
Lease is exclusive to Tenant and shall not pass to any assignee or sublessee
without the express written consent of Landlord. Such consent is at the sole
discretion of the Landlord.

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<PAGE>

          39.1.6 In the event any surcharge or regulatory fee is at any time
imposed by any governmental authority with reference to parking, Tenant shall
(commencing after two (2) weeks' notice to Tenant) pay, per parking pass, such
surcharge or regulatory fee to Landlord in advance on the first day of each
calendar month concurrently with the month installment of rent due under this
Lease. Landlord will enforce any surcharge or fee in an equitable manner amongst
the Building tenants.

          39.1.7 Notwithstanding any provision to the contrary, Tenant shall
have access to an additional twenty (20) parking spaces on month-to-month basis
at the monthly market rate then charged for such spaces. Landlord may terminate
Tenant's rights to any or all of such spaces upon a prior thirty (30) day notice
to Tenant.

          39.1.8 Notwithstanding any provision to the contrary, Tenant shall
have access to two (2) reserved parking spaces in the loading dock area at the
prevailing monthly parking charges.

     39.2 If Tenant violates any of the terms and conditions of this Article,
the operator of the Parking Facility shall have the right to remove from the
Parking Facility any vehicles hereunder which shall have been involved or shall
have been owned or driven by parties involved in causing such violation, without
liability therefore whatsoever. In addition, Landlord shall have the right to
cancel Tenant's right to use the Parking Facility pursuant to this Article upon
ten (10) days' written notice, unless within such ten (10) day period, Tenant
cures such default. Such cancellation right shall be cumulative and in addition
to any other rights or remedies available to Landlord at law or equity, or
provided under this Lease.

40. RENEWAL OPTION. Tenant shall, provided the Lease is in full force and effect
and Tenant is not in default under any of the other terms and conditions of the
Lease at the time of notification or commencement, have one (1) successive
option(s) to renew this Lease for a term of five (5) years each, for the portion
of the Premises being leased by Tenant as of the date the renewal term is to
commence, on the same terms and conditions set forth in the Lease, except as
modified by the terms, covenants and conditions as set forth below:

     40.1 If Tenant elects to exercise said option, then Tenant shall provide
Landlord with written notice no earlier than the date which is eighteen (18)
months days prior to the expiration of the then current term of the Lease but no
later than the date which is nine (9) months prior to the expiration of the then
current term of this Lease. If Tenant fails to provide such notice, Tenant shall
have no further or additional right to extend or renew the term of the Lease.

     40.2 The Annual Rent and Monthly Installment in effect at the expiration of
the then current term of the Lease shall be modified to reflect the current fair
market rental for comparable space in the Building and in other similar
buildings in the same rental market as of the date the renewal term is to
commence, taking into account the specific provisions of the Lease which will
remain constant. Landlord shall advise Tenant of the new Annual Rent and Monthly
Installment for the Premises no later than thirty (30) days after receipt of
Tenant's written request therefor. If Tenant and Landlord are unable to agree on
a mutually acceptable rental rate within forty-five (45) days of exercising the
renewal option, then Landlord and Tenant shall each appoint a qualified
commercial broker with ten (10) years minimum experience as a commercial broker
in the Cambridge market, who shall agree on fair market rent for the renewal
period within thirty (30) days from the expiration of the aforesaid 45 day
period. If the two selected brokers are unable to agree on the fair market rent,
then, within fifteen (15) days from the expiration of the aforesaid 30 day
period, such two brokers shall appoint a third broker with at least ten (10)
years minimum experience as a commercial broker in the Cambridge market. In such
event, within fifteen (15) days of the selection of the third broker, the fair
market rent for the renewal period shall be the average of the two closest fair
market rent determinations for such period of time. Landlord and Tenant shall
each pay for their respective broker's service and, if applicable, equally share
in the expense of the service provided by the third broker. Within ten (10) days
after the brokers' final determination of fair market rent for the renewal
period, but no later than nine (9) months prior to the expiration of the Term,
Tenant may withdraw its exercise of the renewal option, which option then shall
have no further force and effect.

     40.3 This option is not transferable, except as hereinafter provided; the
parties hereto acknowledge and agree that they intend that the aforesaid option
to renew this Lease shall be "personal" to Tenant as set forth above

                                       24

<PAGE>

and that in no event will any assignee or sublessee, except to an Affiliate
pursuant to Section 9.8 of this Lease, have any rights to exercise the aforesaid
option to renew.

     40.4 As each renewal option provided for above is exercised, the number of
renewal options remaining to be exercised is reduced by one and upon exercise of
the last remaining renewal option Tenant shall have no further right to extend
the term of the Lease.

41. RIGHT OF FIRST OFFER. Provided Tenant is not then in default under the
terms, covenants and conditions of the Lease, Tenant shall have the right to
lease any space not leased by Tenant on the balance of the seventh (7th) floor
which becomes available for lease during the Term. In such event, Landlord shall
give written notice to Tenant of the availability of space and the terms and
conditions on which Landlord intends to offer it to the public and Tenant shall
have a period of ten (10) days in which to exercise Tenant's right to lease such
space pursuant to the terms and conditions contained in Landlord's notice,
failing which Landlord may lease such space to any third party on whatever basis
Landlord desires; provided, however, if Landlord, within one hundred twenty
(120) days from the expiration of the aforesaid ten day period, intends to offer
or offers such space under rental terms that are at least ten percent (10%) less
than the rental terms originally offered to Tenant, Landlord shall provide
Tenant with a second notice containing the revised terms and conditions and
Tenant shall have a period of ten (10) days in which to exercise Tenant's right
to lease such space pursuant to the terms and conditions contained in Landlord's
second notice of the revised terms and conditions. Otherwise, Tenant shall have
no further rights with respect to any space on the seventh (7th) floor, not
leased by Tenant. If Tenant exercises its right to lease hereunder, effective as
of the date Landlord delivers the applicable space to Tenant, such space shall
automatically be included within the Premises and subject to all the terms and
conditions of the Lease, except as set forth in Landlord's first or second
notice, whichever is applicable, and as follows:

     41.1 Tenant's Proportionate Share shall be recalculated, using the total
square footage of the Premises, as increased by such space.

     41.2 Such space shall be leased on an "as is" basis and Landlord shall have
no obligation to improve the such space or grant Tenant any improvement
allowance thereon.

     41.3 If requested by Landlord, Tenant shall, prior to the beginning of the
term for such space, execute a written memorandum confirming the inclusion of
such space and the Annual Rent for such space.

42. EXPANSION OPTION. Provided Tenant is not then in default under the terms,
covenants and conditions of the Lease, Tenant shall have the right to lease
approximately seven thousand four hundred sixty-seven (7,467) rentable square
feet on the fifth floor of the Building as shown on Exhibit F (the "Expansion
Premises") provided Tenant gives written notice to Landlord within one (1) year
from the Commencement Date of its exercise of its right to lease the Expansion
Premises and Tenant takes possession of the Expansion Premises within six (6)
months from Landlord's receipt of the aforesaid notice. If Tenant exercises its
right to lease hereunder, effective as of the date Landlord delivers the
Expansion Premises to Tenant, the Expansion Premises shall automatically be
included within the Premises and subject to all the terms and conditions of the
Lease, except as follows:

     42.1 Tenant's Proportionate Share shall be recalculated, using the total
square footage of the Premises, as increased by such space.

     42.2 Such space shall be leased on an "as is" basis and Landlord shall have
no obligation to improve the such space but shall grant to Tenant a fair market
tenant improvement allowance prorated as though the term on the Expansion
Premises were five (5) years, so that, by way of example, if the term is three
(3) years, the allowance is 3/5ths of what it would be for a five (5) year term.

     42.3 The length of the term shall be co-terminus with the Term under this
Lease and the Annual Rent and Monthly Installment of Rent for the Expansion
Premises shall be the then current fair market rental for comparable space in
the Building and in other similar buildings in the same rental market as
determined under Article 40. Any Tenant improvement allowance will be prorated
to the length of the remaining initial Term.

                                       25

<PAGE>

     42.4 If requested by Landlord, Tenant shall, prior to the beginning of the
term for the Expansion Premises, execute a written memorandum confirming the
inclusion of the Expansion Premises and the Annual Rent and Monthly Installment
of Rent.

                                       26

<PAGE>

43. LIMITATION OF LANDLORD'S LIABILITY. Redress for any claim against Landlord
under this Lease shall be limited to and enforceable only against and to the
extent of Landlord's interest in the Building. The obligations of Landlord under
this Lease are not intended to be and shall not be personally binding on, nor
shall any resort be had to the private properties of, any of its or its
investment manager's trustees, directors, officers, partners, beneficiaries,
members, stockholders, employees, or agents, and in no case shall Landlord be
liable to Tenant hereunder for any lost profits, damage to business, or any form
of special, indirect or consequential damages.

LANDLORD:                                  TENANT:

RREEF AMERICA REIT II CORP. PPP,           ART TECHNOLOGY GROUP, INC.,
a Maryland corporation                     a Delaware corporation

By: RREEF Management Company,
    a Delaware corporation,
    Authorized Agent

By: /s/ David F. Crane                     By: /s/ Julie M.B. Bradley
    ------------------------------------       ---------------------------------
Name: David F. Crane                       Name:
                                                 -------------------------------
Title: Vice President - District Manager   Title:
                                                  ------------------------------
Dated:              , 2006                 Dated:             , 2006
       -------------                              ------------

                                       27

<PAGE>

                  EXHIBIT A - FLOOR PLAN DEPICTING THE PREMISES

                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

Exhibits A and A-1 are intended only to show the general layout of the Premises
and the Building as of the beginning of the Term of this Lease. They does not in
any way supersede any of Landlord's rights set forth in Article 17 with respect
to arrangements and/or locations of public parts of the Building and changes in
such arrangements and/or locations. They are not to be scaled; any measurements
or distances shown should be taken as approximate.

                                   (DIAGRAM)

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<PAGE>

                                   (DIAGRAM)

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                                   (DIAGRAM)

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                             EXHIBIT A-1 - SITE PLAN

                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

                                   (DIAGRAM)

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                   EXHIBIT A-2 - LEGAL DESCRIPTION OF THE LOT

                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

A certain parcel of land in the City of Cambridge, Middlesex County,
Massachusetts, bounded and described as follows:

<TABLE>
<S>             <C>
SOUTHWESTERLY   at the intersection of Main Street and First Street, by four
                lines measuring 44.72 feet, 129.49 feet, 24.15 feet, and 41. I6
                feet, respectively;

SOUTHERLY       by Main Street by a line measuring 404.86 feet;

WESTERLY        by Lot 1, by a line measuring 154.28 feet; and

NORTHERLY       by the Broad Canal, 594.60 feet.
</TABLE>

Said parcel is shown as Lot 2 on a "Subdivision Plan of Land in Cambridge, Mass.
(Middlesex County)", dated April 24, 1981, and revised September 4, 1981, drawn
by Boston Survey Consultants, and prepared for Darvel Realty Trust, recorded
with Middlesex Southern District Registry of Deeds in Book 14412, Page 199.

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                        EXHIBIT B -- INITIAL ALTERATIONS

                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

1. Landlord's Work. Tenant's architect shall provide space planning and design
and Landlord shall obtain permits and provide construction of the work described
in Schedule I attached hereto ("Landlord's Work"). Tenant may not use or occupy
the Premises with a number of personnel greater than the building code would
permit. As further provided herein, Tenant shall be responsible for the
incremental cost of Landlord's Work in excess of the Maximum TI Allowance
(defined below). Further, Tenant shall be responsible for the cost and
installation of all of its furniture, fixtures and equipment, including without
limitation all data/telecommunications cabling and wiring. The certificate of
Tenant's architect that the work to be done by Landlord pursuant to this Exhibit
B has been substantially completed shall be adequate evidence that the Premises
have been completed in accordance with the requirements of the Lease and that
possession thereof has been deemed delivered to Tenant, for all purposes of the
Lease, including the commencement of the payment of rent.

2. Cost and Allowance.

     2.1 Within five (5) days after the execution of this Lease, Landlord shall
submit to Tenant for Tenant's approval a written estimate of the cost of
Landlord's Work (an "Estimate"). After obtaining the Estimate, Landlord and
Tenant thereafter shall diligently consult to make such modifications to
Landlord's Work as Tenant determines are necessary to reduce the cost of
Landlord's Work. Within fifteen (15) business days after obtaining the Estimate,
Landlord will obtain from the selected contractor final pricing for the
Landlord's Work (the "Final Pricing") for Tenant's approval. The Final Pricing
shall be based no construction drawings prepared by Tenant's architect and
expected to be delivered to Landlord on May 8, 2006, plus any further
modifications requested by Tenant prior to Tenant's approval of the Final
Pricing. The Final Pricing shall not be modified except by a change order
approved by Landlord and Tenant.

     2.2 Within five (5) business days after Tenant's approval of the Final
Pricing, Landlord may require Tenant to deposit that amount of the amount of the
Final Pricing which exceeds the Maximum TI Allowance (the "Tenant Deposit"). The
Tenant Deposit shall be held by Landlord in escrow in a separate account as
security for the payment of, and shall be credited, without interest, against
the sums payable by Tenant under this Lease. Except for demolition work, which
Landlord will diligently pursue upon complete execution of this Lease, Landlord
shall not be required to commence its other work until the Tenant Deposit is
received, and, for purposes only of determining if Landlord has timely complied
with its construction obligation under Article 2, the Scheduled Commencement
Date shall be extended one (1) day for each day that payment of the Tenant
Deposit is delayed after such five (5) day period.

     2.3 This Lease and the rental rates provided for herein are premised on a
total cost of Landlord's Work not to exceed $1,634,610.00 (the "Maximum TI
Allowance"). The "cost of Landlord's Work" includes, without limitation:

          2.3.1 All costs and expenses actually incurred by Landlord pertaining
to Landlord's Work, including, but not limited to, costs charged by contractors,
subcontractors and general and other conditions costs and expenses in connection
with completing Landlord's Work and otherwise preparing the Premises for
occupancy;

          2.3.2 All costs and expenses, including preparation of the plans as
needed, for such construction, and site inspection and contract administration
by Tenant's onsulting architects and/or engineers;

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                                      B-1

<PAGE>

          2.3.3 All costs of permits, licenses and other approvals required for
the performance of Landlord's Work; and

          2.3.4 A construction management fee to Landlord of two percent (2%) of
the total of all such costs under the foregoing Sections 2.3.1, 2.3.2 and 2.3.3,
but not including any costs exceeding the Maximum TI Allowance.

     2.4 If the total cost of Landlord's Work exceeds the Maximum TI Allowance,
the entire amount of such excess shall be borne by Tenant and shall be paid to
Landlord out of the Tenant Deposit; provided that Tenant shall not be liable to
pay any such excess above the Final Pricing except to the extent such excess if
the result of a change order requested or approved by Tenant. Prior to the
payment of any portion of the Tenant Deposit to Landlord, Tenant's architect
shall certify that the work to be paid for has been completed in accordance with
the plans and specifications included in Schedule I hereto. Notwithstanding the
foregoing, the final One Hundred Thousand Dollars ($100,000) of Tenant's Deposit
(the "Holdback") shall not be released to Landlord until substantial completion
of Landlord's Work, as defined in Section 3 of this Exhibit B. Any portion of
Tenant's Deposit not paid to Landlord pursuant to the provisions of this Exhibit
B shall be returned to Tenant within ten (10) days after substantial completion,
or if substantial completion does not occur, within ten (10) days after written
demand from Tenant.

     2.5 If the total cost of Landlord's Work exceeds the Maximum TI Allowance,
the entire amount of such excess shall be borne by Tenant and shall be paid to
Landlord by Tenant upon demand as additional rent under the Lease. If the total
cost of Landlord's Work is less than the Maximum TI Allowance, the entire amount
of the difference shall be available for Tenant's use for other leasehold
improvements that would remain with the Premises.

     2.6 Tenant and Tenant's construction representative and contractor(s) shall
have access to the Premises during the construction of Landlord's Work for
purposes of inspecting and monitoring the progress of Landlord's Work and for
installing telecommunications, other communications wiring, furniture
installation and security system installation to serve the Premises. Such access
and use of the Premises shall be coordinated with Landlord so as not to
interfere with or delay the completion of Landlord's Work.

3. Substantial Completion of Landlord's Work. Substantial completion of
Landlord's Work shall be evidenced by (i) certification by Tenant's architect as
provided in Section 1 of this Exhibit B; (ii) the issuance of a Certificate of
Occupancy; and (iii) Landlord's and Tenant's agreement on a punch list for work
to be completed by Landlord pursuant to Section 2.1 of this Lease.

4. Miscellaneous.

     4.1 Except as set forth in this Exhibit B, Landlord has no other agreement
with Tenant and has no obligation to do any work with respect to the Premises.
Any other work in the Premises which may be permitted by Landlord pursuant to
the terms and conditions of the Lease shall be done at Tenant's sole cost and
expense and in accordance with the terms and provisions of the Lease.

     4.2 All rights and remedies of Landlord herein created or otherwise
existing at law or equity are cumulative, and the exercise of one or more such
rights or remedies shall not be deemed to exclude or waive the right to the
exercise of any other rights or remedies. All such rights and remedies may be
exercised and enforced concurrently and whenever and as often as deemed
desirable.

     4.3 This Exhibit B shall not be deemed applicable to any additional space
added to the original Premises at any time or from time to time, whether by any
options under the Lease or otherwise, or to any portion of the original Premises
or any additions thereto in the event of a renewal or extension of the original
term of the Lease, whether by any options under the Lease or otherwise.

5. Landlord's Undertakings.

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                                      B-2

<PAGE>

     5.1 Landlord shall keep a complete and accurate accounting of all costs
incurred in connection with the Landlord's Work, and shall provide Tenant with
such accounting (the "Cost Accounting") within forty-five (45) days after the
Premises are Substantially Complete. The Cost Accounting shall be subject to
audit by Tenant within sixty (60) days from receipt of such accounting.

     5.2 Landlord represents and warrants that Landlord's Work shall be
performed in accordance with all applicable laws. Landlord shall, with
reasonable speed and diligence file with the appropriate governmental authority
or authorities all applications for building permits and other required
approvals and shall take whatever reasonable action shall be necessary in
connection with all governmental permits and authorizations which may be
required in connection with Landlord's Work. Landlord shall cause the contractor
selected to undertake the Landlord's Work to obtain all such permits and
authorizations and provide copies of same to Landlord and Tenant. Landlord shall
secure from the contractor a one (1) warranty for the Landlord's Work that
contractor or its subcontractors perform and Landlord will enforce such warranty
upon receipt of timely written notice from Tenant of its need to do so with
specificities relating to such need.

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                                      B-3

<PAGE>

                                   SCHEDULE I

                                 LANDLORD'S WORK

Construction per plans and specifications dated April 21, 2006 and prepared by
Baker Design Group Inc., with such modifications as are shown on the May 8 plans
and specifications to be provided by Tenant's architect, as may be further
modified by the approval of both Landlord and Tenant.

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                                       B-3

<PAGE>

                    EXHIBIT C - COMMENCEMENT DATE MEMORANDUM

                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

                          COMMENCEMENT DATE MEMORANDUM

     THIS MEMORANDUM, made as of __________, 2006, by and between RREEF AMERICA
REIT II CORP. PPP, a Maryland corporation ("Landlord") and ART TECHNOLOGY GROUP,
INC., a Delaware corporation ("Tenant").

                                    Recitals:

     A.   Landlord and Tenant are parties to that certain Lease, dated for
          reference April 12, 2006 (the "Lease") for certain premises (the
          "Premises") consisting of approximately 44,981 square feet of office
          space and 500 square feet of storage at the building commonly known as
          One Main Street, Cambridge, Massachusetts.

     B.   Tenant is in possession of the Premises and the Term of the Lease has
          commenced.

     C.   Landlord and Tenant desire to enter into this Memorandum confirming
          the Commencement Date, the Termination Date and other matters under
          the Lease.

     NOW, THEREFORE, Landlord and Tenant agree as follows:

     1. The actual Commencement Date is ________________.

     2. The actual Termination Date is _________________.

     3. The schedule of the Annual Rent and the Monthly Installment of Rent set
forth on the Reference Pages is deleted in its entirety, and the following is
substituted therefor:

                             [INSERT RENT SCHEDULE]

     4. Capitalized terms not defined herein shall have the same meaning as set
forth in the Lease.

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                                      C-1

<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as of the date and year first above written.

LANDLORD:                                  TENANT:

RREEF AMERICA REIT II CORP. PPP,           ART TECHNOLOGY GROUP, INC.,
a Maryland corporation                     a Delaware corporation

By: RREEF Management Company,
    a Delaware corporation,
    Authorized Agent

By: DO NOT EXECUTE, SAMPLE ONLY            By: DO NOT EXECUTE, SAMPLE ONLY

Name: David F. Crane                       Name:
Title: Vice President - District Manager         -------------------------------
                                           Title:
Dated:                , 2006                      ------------------------------
       ---------------                     Dated:              , 2006
                                                  -------------

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                                      C-2

<PAGE>

                        EXHIBIT D - RULES AND REGULATIONS

                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

1. No sign, placard, picture, advertisement, name or notice shall be installed
or displayed on any part of the outside or inside of the Building without the
prior written consent of the Landlord. Landlord shall have the right to remove,
at Tenant's expense and without notice, any sign installed or displayed in
violation of this rule. All approved signs or lettering on doors and walls shall
be printed, painted, affixed or inscribed at Tenant's expense by a vendor
designated or approved by Landlord. In addition, Landlord reserves the right to
change from time to time the format of the signs or lettering and to require
previously approved signs or lettering to be appropriately altered. Subject to
municipal ordinances and Landlord's approval of size, content, location and
materials, Tenant shall have the right to signage on the lobby directory, on the
6th and 7th floors where the Premises are located and on the exterior
ground-mounted monument sign adjacent to the East Arcade.

2. If Landlord objects in writing to any curtains, blinds, shades or screens
attached to or hung in or used in connection with any window or door of the
Premises, Tenant shall immediately discontinue such use. No awning shall be
permitted on any part of the Premises. Tenant shall not place anything or allow
anything to be placed against or near any glass partitions or doors or windows
which may appear unsightly, in the opinion of Landlord, from outside the
Premises.

3. Tenant shall not obstruct any sidewalks, halls, passages, exits, entrances,
elevators, or stairways of the Building. No tenant and no employee or invitee of
any tenant shall go upon the roof of the Building.

4. Any directory of the Building, if provided, will be exclusively for the
display of the name and location of tenants only and Landlord reserves the right
to exclude any other names. Landlord reserves the right to charge for Tenant's
directory listing.

5. All cleaning and janitorial services for the Building and the Premises shall
be provided exclusively through Landlord. Tenant shall not cause any unnecessary
labor by carelessness or indifference to the good order and cleanliness of the
Premises. Landlord shall not in any way be responsible to any Tenant for any
loss of property on the Premises, however occurring, or for any damage to any
Tenant's property by the janitor or any other employee or any other person.

6. The toilet rooms, toilets, urinals, wash bowls and other apparatus shall not
be used for any purpose other than that for which they were constructed. No
foreign substance of any kind whatsoever shall be thrown into any of them, and
the expense of any breakage, stoppage or damage resulting from the violation of
this rule shall be borne by the Tenant who, or whose employees or invitees,
shall have caused it.

7. Tenant shall store all its trash and garbage within its Premises. Tenant
shall not place in any trash box or receptacle any material which cannot be
disposed of in the ordinary and customary manner of trash and garbage disposal.
All garbage and refuse disposal shall be made in accordance with directions
issued from time to time by Landlord. Tenant will comply with any and all
recycling procedures designated by Landlord.

8. Landlord will furnish Tenant two (2) keys free of charge to each door in the
Premises that has a passage way lock. Landlord may charge Tenant a reasonable
amount for any additional keys, and Tenant shall not make or have made
additional keys on its own. Tenant shall not alter any lock or install a new or
additional lock or bolt on any door of its Premises. Tenant, upon the
termination of its tenancy, shall deliver to Landlord the keys of all doors
which have been furnished to Tenant, and in the event of loss of any keys so
furnished, shall pay Landlord therefor.

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                                      D-1

<PAGE>

9. If Tenant requires telephone, data, burglar alarm or similar service, the
cost of purchasing, installing and maintaining such service shall be borne
solely by Tenant. No boring or cutting for wires will be allowed without the
prior written consent of Landlord.

10. No equipment, materials, furniture, packages, bulk supplies, merchandise or
other property will be received in the Building or carried in the elevators
except between such hours and in such elevators as may be designated by
Landlord. The persons employed to move such equipment or materials in or out of
the Building must be acceptable to Landlord.

11. Tenant shall not place a load upon any floor which exceeds the load per
square foot which such floor was designed to carry and which is allowed by law.
Heavy objects shall stand on such platforms as determined by Landlord to be
necessary to properly distribute the weight. Business machines and mechanical
equipment belonging to Tenant which cause noise or vibration that may be
transmitted to the structure of the Building or to any space in the Building to
such a degree as to be objectionable to Landlord or to any tenants shall be
placed and maintained by Tenant, at Tenant's expense, on vibration eliminators
or other devices sufficient to eliminate the noise or vibration. Landlord will
not be responsible for loss of or damage to any such equipment or other property
from any cause, and all damage done to the Building by maintaining or moving
such equipment or other property shall be repaired at the expense of Tenant.

12. Landlord shall in all cases retain the right to control and prevent access
to the Building of all persons whose presence in the judgment of Landlord would
be prejudicial to the safety, character, reputation or interests of the Building
and its tenants, provided that nothing contained in this rule shall be construed
to prevent such access to persons with whom any tenant normally deals in the
ordinary course of its business, unless such persons are engaged in illegal
activities. Landlord reserves the right to exclude from the Building between the
hours of 6 p.m. and 7 a.m. the following day, or such other hours as may be
established from time to time by Landlord, and on Sundays and legal holidays,
any person unless that person is known to the person or employee in charge of
the Building and has a pass or is properly identified. Tenant shall be
responsible for all persons for whom it requests passes and shall be liable to
Landlord for all acts of such persons. Landlord shall not be liable for damages
for any error with regard to the admission to or exclusion from the Building of
any person.

13. Tenant shall not use any method of heating or air conditioning other than
that supplied or approved in writing by Landlord.

14. Tenant shall not waste electricity, water or air conditioning. Tenant shall
keep corridor doors closed. Tenant shall close and lock the doors of its
Premises and entirely shut off all water faucets or other water apparatus and
electricity, gas or air outlets before Tenant and its employees leave the
Premises. Tenant shall be responsible for any damage or injuries sustained by
other tenants or occupants of the Building or by Landlord for noncompliance with
this rule.

15. Tenant shall not install any radio or television antenna, satellite dish,
loudspeaker or other device on the roof or exterior walls of the Building
without Landlord's prior written consent, which consent may be withheld in
Landlord's sole discretion, and which consent may in any event be conditioned
upon Tenant's execution of Landlord's standard form of license agreement. Tenant
shall be responsible for any interference caused by such installation.

16. Tenant shall not mark, drive nails, screw or drill into the partitions,
woodwork, plaster, or drywall (except for pictures, tackboards and similar
office uses) or in any way deface the Premises. Tenant shall not cut or bore
holes for wires. Tenant shall not affix any floor covering to the floor of the
Premises in any manner except as approved by Landlord. Tenant shall repair any
damage resulting from noncompliance with this rule.

17. Tenant shall not install, maintain or operate upon the Premises any vending
machine without Landlord's prior written consent, except that Tenant may install
food and drink vending machines solely for the convenience of its employees.

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18. No cooking shall be done or permitted by any tenant on the Premises, except
that Underwriters' Laboratory approved microwave ovens or equipment for brewing
coffee, tea, hot chocolate and similar beverages shall be permitted provided
that such equipment and use is in accordance with all applicable federal, state
and city laws, codes, ordinances, rules and regulations.

19. Tenant shall not use in any space or in the public halls of the Building any
hand trucks except those equipped with the rubber tires and side guards or such
other material-handling equipment as Landlord may approve. Tenant shall not
bring any other vehicles of any kind into the Building.

20. Tenant shall not permit any motor vehicles to be washed or mechanical work
or maintenance of motor vehicles to be performed in any parking lot.

21. Tenant shall not use the name of the Building or any photograph or likeness
of the Building in connection with or in promoting or advertising Tenant's
business, except that Tenant may include the Building name in Tenant's address.
Landlord shall have the right, exercisable without notice and without liability
to any tenant, to change the name and address of the Building.

22. Tenant requests for services must be submitted to the Building office by an
authorized individual. Employees of Landlord shall not perform any work or do
anything outside of their regular duties unless under special instruction from
Landlord, and no employee of Landlord will admit any person (Tenant or
otherwise) to any office without specific instructions from Landlord.

23. Tenant shall not permit smoking or carrying of lighted cigarettes or cigars
other than in areas designated by Landlord as smoking areas.

24. Canvassing, soliciting, distribution of handbills or any other written
material in the Building is prohibited and each tenant shall cooperate to
prevent the same. No tenant shall solicit business from other tenants or permit
the sale of any good or merchandise in the Building without the written consent
of Landlord.

25. Tenant shall not permit any animals other than service animals, e.g.
seeing-eye dogs, to be brought or kept in or about the Premises or any common
area of the Building.

26. These Rules and Regulations are in addition to, and shall not be construed
to in any way modify or amend, in whole or in part, the terms, covenants,
agreements and conditions of any lease of any premises in the Building. Landlord
shall uniformly apply and enforce these Rules and Regulations against all of the
tenants of the Building.

27. Landlord reserves the right to make such other and reasonable rules and
regulations as in its judgment may from time to time be needed for safety and
security, for care and cleanliness of the Building, and for the preservation of
good order in and about the Building. Tenant agrees to abide by all such rules
and regulations herein stated and any additional rules and regulations which are
adopted. Tenant shall be responsible for the observance of all of the foregoing
rules by Tenant's employees, agents, clients, customers, invitees and guests.

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                          EXHIBIT E - ELECTRICITY COSTS

                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

      PROCEDURE FOR ALLOCATION OF COSTS OF ELECTRIC POWER USAGE BY TENANTS

     1. Main electric service to the Building will be provided by the local
utility company to a single main meter. All charges by the utility will be read
from this meter and billed to and paid by Landlord at rates established by the
utility company.

     2. In order to allocate charges for electric service fairly among tenants
in relation to the relative amounts of electricity used by each tenant,
additional meters (known as "check meters") will be installed by Landlord for
each tenant to measure all electricity provided for lights and power to that
tenant. This shall not, however, include the following, which shall be wired
from the main Building service and not through the check meters: stairwell and
emergency lights; elevators; heat pumps and HVAC in the Building; exterior
lighting; and all main Building mechanical systems (common areas on each floor,
including the elevator lobby, corridors, and bathrooms, will have service
through the check meters on each floor) (the "Basic Building Electricity") and
which shall be separately metered.

     3. Additional check meters may be installed by Landlord where necessary to
assure measurement of all electric service to tenant areas (e.g., in the case of
separate dedicated circuits to computer rooms, cafeterias, or other special
purpose facilities). Ground floor tenant space will be check-metered if it is
not separately metered. In addition, further modification to the number and
location of check meters may be made by Landlord if required to improve the
quality of information obtained thereby.

     4. Landlord will cause the check meters to be read monthly by its employees
and will perform an analysis of the information for the purpose of determining
an equitable allocation of the costs of electric service among the tenants in
the Building in relation to the respective amounts of usage of electricity by
those tenants.

     5. Each tenant's allocable share ("Tenant's Allocable Electricity Cost"),
shall be determined by Landlord on the following basis:

          (a)  The total kilowatt hour usage for the period under evaluation
               shall be established for each check meter and also for the
               Building as a whole by a reading of the main Building meter for
               that period.

          (b)  The cost of the total amount of electricity supplied for usage by
               tenants during the period (exclusive of the Base Building
               Electricity) (herein called "Tenant Electricity") shall be
               determined by multiplying the total cost of electricity as
               invoiced by the utility company for the same period by a
               fraction, the numerator of which is the total amount of kilowatt
               hour usage as measured by all of the Tenant Electricity check
               meters in the Building and the denominator of which is the total
               amount of kilowatt hour usage for the Building as measured by the
               main Building electric meter.

          (c)  Tenant's Allocable Electricity Cost for the period shall be
               determined by multiplying the total costs of Tenant Electricity
               by a fraction, the numerator of which is the kilowatt hour usage
               of Tenant Electricity by said tenant (calculated as the sum of
               kilowatt hour usage during the period measured by all check
               meters serving its premises) and the denominator of which is the
               total kilowatt hour usage of Tenant Electricity for the same
               period.

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          (d)  Where part or all of the rentable area on a floor has been
               occupied by a tenant for less than all of the period for which
               said Tenant's Allocable Electricity Cost is being calculated,
               appropriate and equitable modifications shall be made to the
               allocation formula so that each tenant's allocable share of costs
               equitably reflects its period of occupancy, provided that in no
               event shall the total of all costs as allocated to tenants be
               less than the total cost of Tenant Electricity for said period.

     6. All costs of Base Building Electricity to Landlord shall be treated as
part of the Expenses of the Building for purposes of determining the allocation
of those costs.

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                         EXHIBIT F - EXPANSION PREMISES
                ATTACHED TO AND MADE A PART OF LEASE BEARING THE
                 LEASE REFERENCE DATE OF APRIL 12, 2006 BETWEEN
                RREEF AMERICA REIT II CORP. PPP, AS LANDLORD AND
                      ART TECHNOLOGY GROUP, INC., AS TENANT

     RIVERFRONT OFFICE PARK, ONE MAIN STREET, CAMBRIDGE, MASSACHUSETTS 02142

                                   (DIAGRAM)

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