<PAGE>   1
                                                                   Exhibit 10.15


                           RIVERVIEW BUILDING COMPLEX
                   245 FIRST STREET, CAMBRIDGE, MASSACHUSETTS


                             OFFICE LEASE AGREEMENT

                                     BETWEEN

                     EOP-RIVERVIEW/245 FIRST STREET, L.L.C.,
                      a Delaware limited liability company
                                  ("LANDLORD")

                                       AND

                           ENGAGE TECHNOLOGIES, INC.,
                             a Delaware corporation
                                   ("TENANT")

<PAGE>   2

                                TABLE OF CONTENTS

<TABLE>
<S>                                                                          <C>
I. Basic Lease Information....................................................1

II. Lease Grant...............................................................4

III. Adjustment of Commencement Date; Possession..............................4

IV. Rent......................................................................4

V. Compliance with Laws; Use..................................................9

VI. Security Deposit..........................................................9

VII. Services to be Furnished by Landlord....................................10

VIII. Leasehold Improvements.................................................11

IX. Repairs and Alterations..................................................12

X. Use of Electrical Services by Tenant......................................13

XI. Entry by Landlord........................................................14

XII. Assignment and Subletting...............................................14

XIII. Liens..................................................................16

XIV. Indemnity and Waiver of Claims..........................................17

XV. Insurance................................................................17

XVI. Subrogation.............................................................18

XVII. Casualty Damage........................................................18

XVIII. Condemnation..........................................................19

XIX. Events of Default.......................................................20

XX. Remedies.................................................................20

XXI. Limitation of Liability.................................................21

XXII. No Waiver..............................................................21

XXIII.  Quiet Enjoyment......................................................21

XXIV. Relocation.............................................................22

XXV. Holding Over............................................................22

XXVI. Subordination to Mortgages; Estoppel Certificate.......................22

XXVII. Attorneys' Fees.......................................................23

XXVIII. Notice...............................................................23

XXIX. Excepted Rights........................................................23

XXX. Surrender of Premises...................................................23

XXXI. Miscellaneous..........................................................24

XXXII. Entire Agreement......................................................25
</TABLE>


                                      -2-
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                             OFFICE LEASE AGREEMENT

     This Office Lease Agreement (the "Lease") is made and entered into as of
the 19th day of June 2000, by and between EOP-RIVERVIEW/245 FIRST STREET,
L.L.C., a Delaware limited liability company ("Landlord") and ENGAGE
TECHNOLOGIES, INC., a Delaware corporation ("Tenant").

I.   Basic Lease Information.

     A.   "Property" shall mean the buildings, Common Areas, as defined in
          Section II of this Lease, serving such buildings (including, at
          Landlord's discretion, the garage and other improvements serving the
          Buildings, if any) and the parcel(s) of land on which the Buildings
          are located which are located at 245 Riverview, Cambridge,
          Massachusetts. The Property contains two (2) buildings, each being
          referred to herein as a "Building, now known as Riverview I and
          Riverview II.

     B.   "Rentable Square Footage" for each Building is deemed to be as
          follows:

                  Riverview I:      109,020 square feet
                  Riverview II:     147,700 square feet
                                    -------
                  Total:            256,720 square feet

     C.   "Premises" shall mean the area shown on Exhibit A to this Lease. The
          Premises are divided into Area A and Area B. Area A is located on
          floor eighteen of Riverview I and is known as suite number(s) . Area B
          is located on floor one of Riverview I and is known as suite number(s)
               . The "Rentable Square Footage of the Premises" is deemed to be
          16,905 square feet for Area A and 15,548 square feet for Area B. If
          the Premises include one or more floors in their entirety, all
          corridors and restroom facilities located on such full floor(s) shall
          be considered part of the Premises. Landlord and Tenant stipulate and
          agree that the Rentable Square Footage of the Buildings and the
          Rentable Square Footage of the Premises are correct and shall not be
          remeasured. Whenever the term "Building" is used in this Lease, such
          term shall be deemed to refer to Riverview I.

     D.   "Base Rent":

          Area A

<TABLE>
<CAPTION>
                                  Annual Rate       Annual         Monthly
          Period                 Per Square Foot   Base Rent      Base Rent
          ------                 ---------------   ---------      ---------
<S>                                 <C>           <C>             <C>
          Commencement Date in      $50.00        $845,250.00     $70,437.50
          respect of Area A -
            January 31, 2006
</TABLE>

          Area B

<TABLE>
<CAPTION>
                                  Annual Rate       Annual         Monthly
          Period                Per Square Foot    Base Rent      Base Rent
          ------                ---------------    ---------      ---------
<S>                                 <C>           <C>             <C>
          February 1, 2001 -        $41.00        $637,468.00     $53,122.34
           January 31, 2002
          February 1, 2002 -        $41.50        $645,242.00     $53,770.17
           January 31, 2003
          February 1, 2003 -        $42.00        $653,016.00     $54,418.00
           January 31, 2004
</TABLE>

                                       1
<PAGE>   4


<TABLE>
<S>                                 <C>           <C>             <C>
          February 1, 2004 -        $42.50        $660,790.00     $55,065.84
           January 31, 2005
          February 1, 2005 -        $43.00        $668,564.00     $55,713.67
           January 31, 2006
</TABLE>

     E.   "Tenant's Pro Rata Building Share":
                        Area A:  15.51%
                        Area B:  14.26%

          "Tenant's Pro Rata Property Share":
                        Area A:  6.58%
                        Area B:  6.07%

     F.   "Building Base Year" (i.e., for "Building Expenses"): Calendar year
          2000

          "Common Area Base Year" (i.e., for "Common Area Expenses"): Calendar
          year 2000

          "Tax Base Year": Fiscal year 2001 (i.e., July 1, 2000 - June 30, 2001)

     G.   "Term":

          Area A:   A period of approximately 67 months. The Term shall commence
          on the Commencement Date in respect of Area A (as hereinafter defined)
          and, unless terminated early in accordance with this Lease, end on
          January 31, 2006 (the "Termination Date"). The Commencement Date in
          respect of Area A shall be one (1) day after the Current Tenant of
          Area A vacates Area A, which is anticipated to be between April 1,
          2000 and July 1, 2000. If the Commencement Date in respect of Area A
          is prior to July 1, 2000, then Landlord shall give Tenant thirty (30)
          days' notice of the Commencement Date in respect of Area A. Promptly
          after the determination of the Commencement Date in respect of Area A,
          Landlord and Tenant shall enter into a commencement letter agreement
          in the form attached as Exhibit C.

          Notwithstanding the foregoing, if the Commencement Date in respect of
          Area A does not occur by October 1, 2000 (the "Area A Outside Date"),
          Tenant, as its sole remedy, may terminate this Lease with respect to
          both Area A and Area B by giving Landlord written notice of
          termination on or before the earlier to occur of: (i) five (5)
          Business Days after the Area A Outside Date; and (ii) the Commencement
          Date in respect of Area A. In such event, this Lease shall be deemed
          null and void and of no further force and effect as of the date of
          Tenant's notice (the "Notice Termination Date") and Landlord shall
          promptly refund any prepaid rent for periods after the Notice
          Termination Date and Security Deposit previously advanced by Tenant
          under this Lease and the parties hereto shall have no further
          responsibilities or obligations to each other with respect to this
          Lease. Landlord and Tenant acknowledge and agree that the Area A
          Outside Date shall be postponed by the number of days the Commencement
          Date is delayed due to events of Force Majeure.

          Area B:   A period of 60 months. The Term shall commence on the
          February 1, 2001 and, unless terminated early in accordance with this
          Lease, end on January 31, 2006 (the "Termination Date").

     H.   Tenant allowance(s): (describe the type and amount of allowance(s), if
          any, and the section(s) where any allowances are defined): None.

     I.   "Security Deposit": $1,112,038.56, subject to reduction pursuant to
          the terms of Section VI.C.

     J.   "Guarantor(s)": None.

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<PAGE>   5

     K.   "Broker(s)": CRF Partners, Inc.

     L.   "Permitted Use": Executive and general offices, including computer and
          data rooms ancillary thereto, for the transaction of Tenant's
          business.

     M.   "Notice Addresses":

          Tenant:

          On and after the Commencement Date, notices shall be sent to Tenant at
          the Premises with copies to the addresses set forth below. Prior to
          the Commencement Date, notices shall be sent to Tenant at the
          following address:

          Tenant:                                         With copies to:

          Engage Technologies, Inc.              CMGI, Inc.
          100 Brickstone Square, 1st Floor       100 Brickstone Square
          Andover, Massachusetts 01810           Andover, Massachusetts 01810
          Attn:  General Counsel                 Attn:  General Counsel

                                                 Hale and Dorr LLP
                                                 60 State Street
                                                 Boston, Massachusetts  02109
                                                 Attn:  Pamela Coravos, Esq.

          Landlord:                              With a copy to:

          EOP-245 First Street, L.L.C.           Equity Office Properties
          c/o Equity Office Properties           Two North Riverside Plaza
          245 First Street                       Suite 2200
          Cambridge, Massachusetts 02142         Chicago, Illinois 60606
          Attention:  Building Manager           Attention:  Northeast Regional
                                                 Counsel


          Rent (defined in Section IV.A) is payable to the order of Equity
          Office Properties at the following address:

                      EOP Operating Limited Partnership,
                      as Agent for EOP-Riverview/245 First Street, L.L.C.
                      P.O. Box 30376
                      Hartford, Connecticut 06150-0376

     N.   "Business Day(s)" are Monday through Friday of each week, exclusive of
          New Year's Day, Memorial Day, Independence Day, Labor Day,
          Thanksgiving Day and Christmas Day ("Holidays"). Landlord may
          designate additional Holidays, provided that the additional Holidays
          are commonly recognized by other office buildings in the area where
          the Building is located.

     O.   "Landlord Work" means the work, if any, that Landlord is obligated to
          perform in the Premises pursuant to a separate work letter agreement
          (the "Work Letter"), if any, attached as Exhibit D. If a Work Letter
          is not attached to this Lease or if an attached Work Letter does not
          require Landlord to perform any work, the occurrence of the
          Commencement Date shall not be conditioned upon the performance of
          work by Landlord and, accordingly, Section III.A. shall not be
          applicable to the determination of the Commencement Date.

     P.   "Law(s)" means all applicable statutes, codes, ordinances, orders,
          rules and regulations of any municipal or governmental entity.

                                       3
<PAGE>   6

     Q.   "Normal Business Hours" for the Building are 8:00 A.M. to 6:00 P.M. on
          Business Days and 9:00 A.M. to 12:00 P.M. on Saturdays.

     R.   "Property" means the Building and the parcel(s) of land on which it is
          located and, at Landlord's discretion, the Building garage and other
          improvements serving the Building, if any, and the parcel(s) of land
          on which they are located.

     S.   "Fiscal Year" means the period July 1 to June 30.

II.  Lease Grant.

     Landlord leases the Premises to Tenant and Tenant leases the Premises from
Landlord, together with the right in common with others to use any portions of
the Property that are designated by Landlord for the common use of tenants and
others, such as sidewalks, unreserved parking areas, common corridors, elevator
foyers, restrooms, vending areas and lobby areas (the "Common Areas").

III. Adjustment of Commencement Date; Possession.

     A.   Intentionally Omitted

     B.   Subject to Landlord's obligations under Section IX.B. and Landlord's
          obligation to deliver the Premises broom clean and free of all
          property of any predecessor tenant, the Premises are accepted by
          Tenant in "as is" condition and configuration. By taking possession of
          the Premises, Tenant agrees that the Premises are in good order and
          satisfactory condition, and that except as expressly set forth herein,
          there are no representations or warranties by Landlord regarding the
          condition of the Premises or the Building. If Landlord is delayed
          delivering possession of the Premises or any other space due to the
          holdover or unlawful possession of such space by any party, Landlord
          shall use reasonable efforts to obtain possession of the space. The
          Commencement Date shall be postponed until the date Landlord delivers
          possession of the Premises to Tenant free from occupancy by any party,
          and the Termination Date, at the option of Tenant or Landlord, may be
          postponed by an equal number of days. Landlord hereby represents and
          warrants to Tenant that (a) the heating/ventilating/air conditioning
          system servicing the Premises is in good operating condition, and (b)
          to the best of Landlord's knowledge, there is no asbestos in the
          ceiling or floor tiles or any other areas within the Premises or in
          adjacent common areas. Landlord shall be solely responsible for any
          repairs or replacements necessary if the foregoing representations are
          not, in fact, true. Such repairs or replacements shall be Tenant's
          sole remedy at law or in equity for any breach of the foregoing
          representations, except for Landlord's bad faith or willful
          misrepresentation.

     C.   If Tenant takes possession of the Premises before the Commencement
          Date, such possession shall be subject to the terms and conditions of
          this Lease and Tenant shall pay Rent (defined in Section IV.A.) to
          Landlord for each day of possession before the Commencement Date.
          However, except for the cost of services requested by Tenant (e.g.
          freight elevator usage), Tenant shall not be required to pay Rent for
          any days of possession before the Commencement Date during which
          Tenant, with the approval of Landlord, is in possession of the
          Premises for the sole purpose of performing improvements or installing
          furniture, equipment or other personal property.

IV.  Rent.

     A.   PAYMENTS. As consideration for this Lease, Tenant shall pay Landlord,
          without any setoff or deduction except as may be expressly set forth
          in this Lease, the total amount of Base Rent and Additional Rent due
          for the Term. "Additional Rent" means all sums (exclusive of Base
          Rent) that Tenant is required to pay Landlord. Additional Rent and
          Base Rent are sometimes collectively referred to as "Rent". Tenant
          shall pay and be liable for all rental, sales and use taxes (but
          excluding income taxes), if any, imposed upon or measured by Rent
          under applicable Law.

                                       4
<PAGE>   7

          Base Rent and recurring monthly charges of Additional Rent shall be
          due and payable in advance on the first day of each calendar month
          without notice or demand, provided that the installment of Base Rent
          for the first full calendar month of the Term shall be payable upon
          the execution of this Lease by Tenant. All other items of Rent shall
          be due and payable by Tenant on or before 30 days after billing by
          Landlord. All payments of Rent shall be by good and sufficient check
          or by other means (such as automatic debit or electronic transfer)
          acceptable to Landlord. If Tenant fails to pay any item or installment
          of Rent when due, Tenant shall pay Landlord an administration fee
          equal to 5% of the past due Rent, provided that Tenant shall be
          entitled to a grace period of 5 days for the first 2 late payments of
          Rent in a given calendar year. If the Term commences on a day other
          than the first day of a calendar month or terminates on a day other
          than the last day of a calendar month, the monthly Base Rent and
          Tenant's Pro Rata Share of any Tax Excess (defined in Section IV.B.)
          or Expense Excess (defined in Section IV.B.) for the month shall be
          prorated based on the number of days in such calendar month.
          Landlord's acceptance of less than the correct amount of Rent shall be
          considered a payment on account of the earliest Rent due. No
          endorsement or statement on a check or letter accompanying a check or
          payment shall be considered an accord and satisfaction, and either
          party may accept the check or payment without prejudice to that
          party's right to recover the balance or pursue other available
          remedies. Except as may be expressly otherwise set forth in this
          Lease, Tenant's covenant to pay Rent is independent of every other
          covenant in this Lease.

     B.   EXPENSE EXCESS AND TAX EXCESS. Tenant shall pay the sum ("Expense
          Excess") of: (i) Tenant's Pro Rata Building Share of the amount, if
          any, by which Building Expenses (defined in Section IV.C.) for each
          calendar year during the Term exceed Building Expenses for the
          Building Base Year, plus (ii) Tenant's pro Rata property Share of the
          amount, if any, by which Common Area Expenses (defined in Section
          IV.C.) for each calendar year during the Term exceed Expenses for the
          Common Area Base Year; and also the amount ("Tax Excess"), if any,
          equal to Tenant's Pro Rata Property Share of the amount, if any, by
          which Taxes (defined in Section IV.D.) for each Fiscal Year during the
          Term exceed Taxes for the Tax Base Year. If Building Expenses in any
          calendar year decrease below the amount of Building Expenses for the
          Building Base Year, Tenant's Pro Rata Building Share of Building
          Expenses for that calendar year shall be $0; if Common Area Expenses
          in any calendar year decrease below the amount of Common Area Expenses
          for the Common Area Base Year, Tenant's Pro Rata Property Share of
          Common Area Expenses for that calendar year shall be $0; if Tenant's
          Property Share of Taxes in any Fiscal year decrease below the amount
          of Taxes for the Tax Base Year, Tenant's Pro Rata Property Share of
          Taxes for that Fiscal year shall be $0. Landlord shall provide Tenant
          with a good faith written estimate of the Expense Excess and of the
          Tax Excess for each calendar year during the Term. On or before the
          first day of each month, Tenant shall pay to Landlord a monthly
          installment equal to one-twelfth of Landlord's estimate of the Expense
          Excess and one-twelfth of Landlord's estimate of the Tax Excess. If
          Landlord determines that its good faith estimate of the Expense Excess
          or of the Tax Excess was incorrect by a material amount, Landlord may
          provide Tenant with a revised estimate. After its receipt of the
          revised estimate, Tenant's monthly payments shall be based upon the
          revised estimate. If Landlord does not provide Tenant with an estimate
          of the Expense Excess or of the Tax Excess by January 1 of a calendar
          year, Tenant shall continue to pay monthly installments based on the
          previous year's estimate(s) until Landlord provides Tenant with the
          new estimate. Upon delivery of the new estimate, an adjustment shall
          be made for any month for which Tenant paid monthly installments based
          on the previous year's estimate(s). Tenant shall pay Landlord the
          amount of any underpayment within 30 days after receipt of the new
          estimate. Any overpayment shall be refunded to Tenant within 30 days
          or credited against the next due future installment(s) of Additional
          Rent. Notwithstanding the fact that Tax Excess is calculated on a
          Fiscal Year basis, Landlord shall be entitled to bill Tenant for such
          amounts following the end of each calendar year at the same time that
          Tenant will be billed for Expense Excess. For example, during the
          calendar year 2001, Tenant, on a monthly basis as

                                       5
<PAGE>   8

          provided below, shall pay Landlord an amount equal to one-twelfth
          (1/12) of the estimated amount by which Tenant's Pro Rata Property
          Share of Taxes for the Fiscal Year 2002 (7/1/01 - 6/30/02) will exceed
          Taxes for the Tax Base Year. Following the date on which Landlord
          receives the quarterly tax bill with respect to the actual amount of
          Taxes for Fiscal Year 2002, Landlord, as provided below, shall provide
          Tenant with a reconciliation of Tenant's actual amount of Tax Excess
          in respect of Fiscal Year 2002. Such reconciliation statement may be
          sent by Landlord separately or together with Landlord's reconciliation
          of Expense Excess for calendar year 2001. In no event shall Tenant be
          required to pay any amount of Expense Excess that is shown on a bill
          first submitted by Landlord to Tenant more than three (3) years after
          the end of the calendar year in which such cost was incurred by
          Landlord.

     C.   EXPENSES DEFINED. "Expenses" means all costs and expenses incurred in
          each calendar year in connection with operating, maintaining,
          repairing, and managing the Buildings and the Property and the
          Complex, including, but not limited to:

          1.   Labor costs, including, wages, salaries, social security and
               employment taxes, medical and other types of insurance, uniforms,
               training, and retirement and pension plans.

          2.   Management fees, the cost of equipping and maintaining a
               management office, accounting and bookkeeping services, legal
               fees not attributable to leasing or collection activity, and
               other administrative costs. Landlord, by itself or through an
               affiliate, shall have the right to directly perform or provide
               any services under this Lease (including management services),
               provided that the cost of any such services shall not exceed the
               cost that would have been incurred had Landlord entered into an
               arms-length contract for such services with an unaffiliated
               entity of comparable skill and experience. In addition, any
               increase in management fees above the management fees included in
               Expenses in the Base Year shall not exceed those arms-length fees
               commonly charged for the management of comparable buildings
               offering comparable services in the Boston financial district.

          3.   The cost of services, including amounts paid to service providers
               and the rental and purchase cost of parts, supplies, tools and
               equipment.

          4.   Premiums and deductibles paid by Landlord for insurance,
               including workers compensation, fire and extended coverage,
               earthquake, general liability, rental loss, elevator, boiler and
               other insurance customarily carried from time to time by owners
               of comparable office buildings.

          5.   Electrical Costs (defined below) and charges for water, gas,
               steam and sewer, but excluding those charges for which Landlord
               is reimbursed by tenants. "Electrical Costs" means: (a) charges
               paid by Landlord for electricity; (b) costs incurred in
               connection with an energy management program for the Property and
               Complex; and (c) if and to the extent permitted by Law, a fee for
               the services provided by Landlord in connection with the
               selection of utility companies and the negotiation and
               administration of contracts for electricity, provided that such
               fee shall not exceed 50% of any savings obtained by Landlord,
               where "savings" shall have the meaning set forth in Article X.A
               hereof. Electrical Costs shall be adjusted as follows: (i)
               amounts received by Landlord as reimbursement for above standard
               electrical consumption shall be deducted from Electrical Costs;
               (ii) the cost of electricity incurred to provide overtime HVAC to
               specific tenants (as reasonably estimated by Landlord) shall be
               deducted from Electrical Costs; and (iii) if Tenant is billed
               directly for the cost of building standard electricity to the
               Premises as a separate charge in addition to Base Rent, the cost
               of electricity to individual tenant spaces in the Building shall
               be deducted from Electrical Costs.

          6.   The amortized cost of capital improvements (as distinguished from
               replacement parts or components installed in the ordinary course
               of business)

                                       6
<PAGE>   9

               made to the Property and Complex which are: (a) performed
               primarily to reduce operating expense costs or otherwise improve
               the operating efficiency of the Property and Complex; or (b)
               required to comply with any Laws that are enacted, or first
               interpreted to apply to the Property, after the date of this
               Lease. The cost of capital improvements shall be amortized by
               Landlord over the lesser of the Payback Period (defined below) or
               10 years. The amortized cost of capital improvements may, at
               Landlord's option, include actual or imputed interest at the rate
               that Landlord would reasonably be required to pay to finance the
               cost of the capital improvement. "Payback Period" means the
               reasonably estimated period of time that it takes for the cost
               savings resulting from a capital improvement to equal the total
               cost of the capital improvement. Notwithstanding the foregoing,
               the portion of the annual amortized costs to be included in
               Expenses in any calendar year with respect to a capital
               improvement which is intended to reduce expenses or improve the
               operating efficiency of the Property or Building shall equal the
               lesser of: a) such annual amortized costs; and b) the projected
               annual amortized reduction in expenses for that portion of the
               amortization period of the capital improvement which falls within
               the Lease Term (based on the total cost savings for such period,
               as reasonably estimated by Landlord).

          If Landlord incurs Expenses for the Property together with one or more
          other buildings or properties, whether pursuant to a reciprocal
          easement agreement, common area agreement or otherwise, the shared
          costs and expenses shall be equitably prorated and apportioned between
          the Property and the other buildings or properties.

          Tenant acknowledges that Expenses ("Common Area Expenses") relating to
          the Common Areas are allocated among all of the office tenants of the
          Property, and that Expenses ("Building Expenses") for each Building
          are allocated among the office tenants of such Building. Expenses
          shall be allocated among Common Area Expenses and Building Expenses
          for each Building in such manner as Landlord shall reasonably
          determined.

          Expenses shall not include: the cost of capital improvements (except
          as set forth above); depreciation; interest (except as provided above
          for the amortization of capital improvements); principal payments of
          mortgage and other non-operating debts of Landlord; the cost of
          repairs or other work to the extent Landlord is reimbursed by
          insurance or condemnation proceeds; costs in connection with leasing
          space in the Buildings, including brokerage commissions; lease
          concessions, including rental abatements and construction allowances,
          granted to specific tenants; costs incurred in connection with the
          sale, financing or refinancing of the Buildings; fines, interest and
          penalties incurred due to the late payment of Taxes (defined in
          Section IV.D) or Expenses; organizational expenses associated with the
          creation and operation of the entity which constitutes Landlord; any
          penalties or damages that Landlord pays to Tenant under this Lease or
          to other tenants in the Building under their respective leases; or any
          of the items designated as Excluded Costs on Exhibit F attached
          hereto. If either Building is not at least 95% occupied during any
          calendar year or if Landlord is not supplying services to at least 95%
          of the total Rentable Square Footage of either Building at any time
          during a calendar year, Expenses shall, at Landlord's option, be
          determined as if such Building had been 95% occupied and Landlord had
          been supplying services to 95% of the Rentable Square Footage of such
          Building during that calendar year. If Expense Excess for a calendar
          year is determined as provided in the prior sentence, Building
          Expenses for the Building Base Year and, if applicable, Common Area
          Expenses for the Common Area Base Year shall also be determined as if
          such Building had been 95% occupied and Landlord had been supplying
          services to 95% of the Rentable Square Footage of such Building. The
          extrapolation of Expenses under this Section shall be performed by
          appropriately adjusting the cost of those components of Expenses that
          are impacted by changes in the occupancy of the Building in question.

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<PAGE>   10

     D.   TAXES DEFINED. "Taxes" shall mean: (1) all real estate taxes and other
          assessments on the Buildings and/or Property, including, but not
          limited to, assessments for special improvement districts and building
          improvement districts, taxes and assessments levied in substitution or
          supplementation in whole or in part of any such taxes and assessments
          and the Property's share of any real estate taxes and assessments
          under any reciprocal easement agreement, common area agreement or
          similar agreement as to the Property; (2) all personal property taxes
          for property that is owned by Landlord and used in connection with the
          operation, maintenance and repair of the Property; and (3) all costs
          and fees incurred in connection with seeking reductions in any tax
          liabilities described in (1) and (2), including, without limitation,
          any costs incurred by Landlord for compliance, review and appeal of
          tax liabilities. The parties acknowledge that, as of the Execution
          Date of this Lease, the Property is assessed as a single tax parcel by
          the City of Cambridge, even though there are two (2) Buildings located
          on the Property. Without limitation, Taxes shall not include (i) any
          income, capital levy, franchise, capital stock, gift, estate or
          inheritance tax, or (ii) interest or penalties incurred by Landlord as
          a result of Landlord's late payment of Taxes. If an assessment is
          payable in installments, Taxes for the year shall include only the
          amount of the installment and any interest due and payable during that
          year. For all other real estate taxes, Taxes for that year shall, at
          Landlord's election, include either the amount accrued, assessed or
          otherwise imposed for the year or the amount due and payable for that
          year, provided that Landlord's election shall be applied consistently
          throughout the Term. If a change or abatement in Taxes is obtained for
          any year of the Term during which Tenant paid any Tax Excess, then
          Taxes for that year will be retroactively adjusted and Landlord shall
          provide Tenant with a credit, if any, against the payment of
          Additional Rent based on the adjustment. Likewise, if a change or
          abatement is obtained for Taxes for the Tax Base Year, Taxes for the
          Tax Base Year shall be restated and the Tax Excess for all subsequent
          years shall be recomputed. Tenant shall pay Landlord the amount of any
          such increase in Tax Excess within 30 days after Tenant's receipt of a
          statement from Landlord.

     E.   AUDIT RIGHTS. Tenant may, within 90 days after receiving Landlord's
          statement of Expenses, give Landlord written notice ("Review Notice")
          that Tenant intends to review Landlord's records of the Expenses for
          that calendar year. Within a reasonable time after receipt of the
          Review Notice, Landlord shall make all pertinent records available for
          inspection that are reasonably necessary for Tenant to conduct its
          review. If any records are maintained at a location other than the
          office of the Building, Tenant may either inspect the records at such
          other location or pay for the reasonable cost of copying and shipping
          the records. If Tenant retains an agent to review Landlord's records,
          the agent must be with a licensed CPA firm. Tenant shall be solely
          responsible for all costs, expenses and fees incurred for the audit.
          Within 90 days after the records are made available to Tenant, Tenant
          shall have the right to give Landlord written notice (an "Objection
          Notice") stating in reasonable detail any objection to Landlord's
          statement of Expenses for that year. If Tenant fails to give Landlord
          an Objection Notice within the 90 day period or fails to provide
          Landlord with a Review Notice within the 90 day period described
          above, Tenant shall be deemed to have approved Landlord's statement of
          Expenses and shall be barred from raising any claims regarding the
          Expenses for that year. If Tenant provides Landlord with a timely
          Objection Notice, Landlord and Tenant shall work together in good
          faith to resolve any issues raised in Tenant's Objection Notice. If
          Landlord and Tenant determine that Expenses for the calendar year are
          less than reported, Landlord shall provide Tenant with a credit
          against the next installment of Rent in the amount of the overpayment
          by Tenant. In addition, if Landlord and Tenant determine that Expenses
          for the Building were less than stated by more than five percent (5%),
          Landlord, within thirty (30) days after its receipt of paid invoices
          therefor from Tenant, shall reimburse Tenant for any reasonable
          amounts paid by Tenant to third parties in performing such review by
          Tenant. Likewise, if Landlord and Tenant determine that Expenses for
          the calendar year are greater than reported, Tenant shall pay Landlord
          the amount of any underpayment within 30 days. The records obtained by
          Tenant shall be treated as confidential. In no

                                       8
<PAGE>   11

          event shall Tenant be permitted to examine Landlord's records or to
          dispute any statement of Expenses unless Tenant has paid and continues
          to pay all Rent when due.

V.   Compliance with Laws; Use.

     The Premises shall be used only for the Permitted Use and for no other use
whatsoever. Tenant shall not use or permit the use of the Premises for any
purpose which is illegal, dangerous to persons or property or which, in
Landlord's reasonable opinion, unreasonably disturbs any other tenants of the
Building or interferes with the operation of the Building. Tenant shall comply
with all Laws, including the Americans with Disabilities Act, regarding the
operation of Tenant's business and the use, condition, configuration and
occupancy of the Premises. Tenant, within 10 days after receipt, shall provide
Landlord with copies of any notices it receives regarding a violation or alleged
violation of any Laws. Tenant shall comply with the rules and regulations of the
Building attached as Exhibit B and such other reasonable rules and regulations
adopted by Landlord from time to time. Tenant shall also cause its agents,
contractors, subcontractors, employees, customers, and subtenants to comply with
all rules and regulations. Landlord agrees not to enforce such rules and
regulations in a manner that unreasonably discriminates against Tenant,
recognizing that differing circumstances may justify different treatment.

     Notwithstanding the foregoing, Landlord, at its sole cost and expense
(except to the extent properly included in Expenses), shall be responsible for
correcting any violations of Title III of the Americans with Disabilities Act
with respect to the Premises and the Common Areas of the Building, provided that
Landlord's obligation with respect to the Premises shall be limited to
violations that arise out of the Landlord Work and/or the condition of the
Premises prior to the installation of any furniture, equipment and other
personal property of Tenant. Notwithstanding the foregoing, Landlord shall have
the right to contest any alleged violation in good faith, including, without
limitation, the right to apply for and obtain a waiver or deferment of
compliance, the right to assert any and all defenses allowed by law and the
right to appeal any decisions, judgments or rulings to the fullest extent
permitted by law. Landlord, after the exhaustion of any and all rights to appeal
or contest, will make all repairs, additions, alterations or improvements
necessary to comply with the terms of any final order or judgment.
Notwithstanding the foregoing, Tenant, not Landlord, shall be responsible for
the correction of any violations that arise out of or in connection with any
claims brought under any provision of the Americans with Disabilities Act other
than Title III which (i) arise out of the specific nature of Tenant's business
in the Premises (other than general office use), (ii) arise out of the acts or
omission of Tenant, its agents, employees and contractors, (iii) arise out of
Tenant's arrangement of any furniture, equipment or other property in the
Premises, or any repairs, alterations, additions or improvements performed by or
on behalf of Tenant (other than the Landlord Work) and (iv) arise out of any
design or configuration of the Premises specifically requested by Tenant after
being informed that such design or configuration may not be in strict compliance
with the ADA.

VI.  Security Deposit.

     A.   The Security Deposit shall be delivered to Landlord upon the execution
          of this Lease by Tenant and shall be held by Landlord without
          liability for interest (unless required by Law) as security for the
          performance of Tenant's obligations. The Security Deposit is not an
          advance payment of Rent or a measure of Tenant's liability for
          damages. Landlord may, from time to time, without prejudice to any
          other remedy, use all or a portion of the Security Deposit to satisfy
          past due Rent or to cure any uncured default by Tenant. If Landlord
          uses the Security Deposit, Tenant shall on demand restore the Security
          Deposit to its original amount. Landlord shall return any unapplied
          portion of the Security Deposit to Tenant within 45 days after the
          later to occur of: (1) the determination of Tenant's Pro Rata Share of
          any Tax Excess and Expense Excess for the final year of the Term; (2)
          the date Tenant surrenders possession of the Premises to Landlord in
          accordance with this Lease; or (3) the Termination Date. If Landlord
          transfers its

                                       9
<PAGE>   12

          interest in the Premises, Landlord may assign the Security Deposit to
          the transferee and, following the assignment and acceptance of the
          Security Deposit by such transferee, Landlord shall have no further
          liability for the return of the Security Deposit. Landlord shall not
          be required to keep the Security Deposit separate from its other
          accounts.

     B.   The Security Deposit may be in the form of an irrevocable letter of
          credit (the "Letter of Credit"), which Letter of Credit shall: (a) be
          in the amount of $1,112,038.56; (b) be in form and substance
          satisfactory to Landlord; (c) name Landlord as its beneficiary; (d) be
          drawn on an FDIC insured financial institution satisfactory to the
          Landlord; (e) expressly allow Landlord to draw upon it: (i) in the
          event that the Tenant is in default under the Lease by delivering to
          the issuer of the Letter of Credit written notice that Landlord is
          entitled to draw thereunder pursuant to the terms of this Lease; or
          (ii) if Tenant, within sixty (60) days prior to expiration of the
          Letter of Credit then held by Landlord, fails to provide Landlord with
          a replacement Letter of Credit meeting the requirements herein; (f)
          expressly state that it will be honored by the issuer without inquiry
          into the accuracy of any such notice or statement made by Landlord;
          (g) expressly permit multiple or partial draws up to the stated amount
          of the Letter of Credit; (h) expressly provide that it is transferable
          to any successor of Landlord; and (i) expire no earlier than sixty
          (60) days after the Termination Date of this Lease. Notwithstanding
          the foregoing, Landlord hereby approves BankBoston or Fleet Bank as
          the issuer of the Letter of Credit and the form of Letter of Credit
          attached hereto as EXHIBIT G. If Landlord intends to assign Landlord's
          interest in the Lease, Tenant shall, upon notice from Landlord,
          deliver to Landlord an amendment to the Letter of Credit naming
          Landlord's assignee as the beneficiary thereof. If Tenant fails to
          deliver such amendment within ten (10) business days after notice from
          Landlord, Landlord shall have the right to draw down the entire amount
          of the Letter of Credit and hold the proceeds thereof as a Security
          Deposit in accordance with this Section VI.

     C.   Notwithstanding anything herein to the contrary, provided (i) Tenant
          is not in default under this Lease as of the effective date of any
          reduction of the Security Deposit, and (ii) Tenant's so-called
          "current ratio" of assets to liabilities is at least 2.0:1 as of the
          effective date of any reduction of the Security Deposit, Tenant shall
          have the right to reduce the amount of the Security Deposit (or the
          amount of the Letter of Credit, if applicable) to be as follows: (i)
          $741,359.04 effective as of January 1, 2002; (ii) $617,799.20
          effective as of January 1, 2003; (iii) $494,239.36 effective as of
          January 1, 2004; (iv) $370,679.52 effective as of January 1, 2005 ;and
          (v) $247,119.68 effective as of January 1, 2006. Such reduction (x) in
          the case of a Letter of Credit, shall be accomplished by having Tenant
          provide Landlord with a substitute Letter of Credit in the reduced
          amount, and otherwise meeting all of the conditions set forth above,
          and (y) in the case of a cash Security Deposit, shall be accomplished
          as follows: Tenant shall have the right to provide Landlord with
          written notice requesting that the Security Deposit be reduced as
          provided above (the "Reduction Notice"). If Tenant provides Landlord
          with a Reduction Notice, Landlord shall refund the applicable portion
          of the Security Deposit to Tenant within forty-five (45) days after
          the later to occur of (i) Landlord's receipt of the Reduction Notice,
          or (ii) the date upon which Tenant is entitled to a reduction in the
          Security Deposit as provided above.

VII. Services to be Furnished by Landlord.

     A.   Landlord agrees to furnish Tenant with the following services, which
          services shall be in quantity and quality consistent with services
          provided in comparable first class office buildings in the
          Cambridge/Boston area: (1) Water service for use in the lavatories on
          each floor on which the Premises are located; (2) Heat, ventilation
          and air conditioning in season during Normal Business Hours, at such
          temperatures and in such amounts as are standard for comparable
          buildings or as required by governmental authority. Tenant, upon such
          advance notice as is reasonably required by Landlord, shall have the
          right to receive HVAC service during hours other than Normal Business
          Hours. Tenant shall pay Landlord the standard charge for the
          additional service as reasonably determined by Landlord

                                       10
<PAGE>   13

          from time to time; (3) Maintenance and repair of the Property as
          described in Section IX.B.; (4) Janitor service on Business Days. If
          Tenant's use, floor covering or other improvements require special
          services in excess of the standard services for the Building, Tenant
          shall pay the additional cost attributable to the special services;
          (5) Elevator service (which shall be available at all times, except in
          case of emergency, but may be on a limited basis outside of Normal
          Business Hours); (6) Electricity to the Premises for general office
          use, in accordance with and subject to the terms and conditions in
          Article X; and (7) such other services as Landlord reasonably
          determines are necessary or appropriate for the Property.

     B.   Landlord shall make available to Tenant for its non-exclusive use
          telecommunication riser access at a riser terminating at the
          telecommunications closets located on each floor of the Premises. The
          riser provided to Tenant shall provide reasonably sufficient access to
          allow Tenant to bring T1/T3 lines to the Premises. Tenant shall be
          responsible, at its sole cost and expense (including the cost of
          installing any required conduits) of installing such T1/T3 lines. Any
          installation of equipment, conduit or cabling by Tenant in such riser
          shall be subject to Landlord's reasonable approval.

     C.   Landlord's failure to furnish, or any interruption or termination of,
          services due to the application of Laws, the failure of any equipment,
          the performance of repairs, improvements or alterations, or the
          occurrence of any event or cause beyond the reasonable control of
          Landlord (a "Service Failure") shall not render Landlord liable to
          Tenant, constitute a constructive eviction of Tenant, give rise to an
          abatement of Rent, nor relieve Tenant from the obligation to fulfill
          any covenant or agreement. However, if the Premises, or a material
          portion of the Premises, is made untenantable for a period in excess
          of 3 consecutive Business Days as a result of the Service Failure,
          then Tenant shall be entitled to receive an abatement of Rent payable
          hereunder during the period beginning on the 4th consecutive Business
          Day of the Service Failure and ending on the day the service has been
          restored. If the entire Premises has not been rendered untenantable by
          the Service Failure, the amount of abatement that Tenant is entitled
          to receive shall be prorated based upon the percentage of the Premises
          rendered untenantable and not used by Tenant. In no event, however,
          shall Landlord be liable to Tenant for any loss or damage, including
          the theft of Tenant's Property (defined in Article XV), arising out of
          or in connection with the failure of any security services, personnel
          or equipment. In the event that the Service Failure continues for more
          than two hundred seventy (270) days, then Tenant shall have the right
          to elect to terminate this Lease within ten (10) days after the
          expiration of said two hundred seventy (270) day period without
          penalty, by delivering written notice to Landlord of its election
          thereof; provided, however, if Landlord is diligently pursuing the
          repair or restoration of the service, Tenant shall not be entitled to
          terminate the Lease but rather Tenant's sole remedy shall be to abate
          Rent. The abatement of Rent and the termination right provided for in
          this Article VII shall be Tenant's sole remedies in the event of a
          Service Failure.

VIII. Leasehold Improvements.

     All Tenant's furniture, fixtures and equipment shall remain the property of
Tenant and Tenant may remove the same at any time on or before the Termination
Date. All improvements to the Premises (collectively, "Leasehold Improvements")
shall be owned by Landlord and shall remain upon the Premises without
compensation to Tenant. However, Landlord, by written notice to Tenant within 30
days prior to the Termination Date, may require Tenant to remove, at Tenant's
expense: (1) Cable (defined in Section IX.A) installed by or for the exclusive
benefit of Tenant and located in the Premises or other portions of the Building;
and (2) any Leasehold Improvements that are performed by or for the benefit of
Tenant and, in Landlord's reasonable judgment, are of a nature that would
require removal and repair costs that are materially in excess of the removal
and repair costs associated with standard office improvements (collectively
referred to as "Required Removables"). Without limitation, it is agreed that
Required Removables include internal stairways, raised floors, personal baths
and showers, vaults, rolling file systems and structural alterations and
modifications of any type. The Required

                                       11
<PAGE>   14

Removables designated by Landlord shall be removed by Tenant before the
Termination Date, provided that upon prior written notice to Landlord, Tenant
may remain in the Premises for up to 5 days after the Termination Date for the
sole purpose of removing the Required Removables. Tenant's possession of the
Premises shall be subject to all of the terms and conditions of this Lease,
including the obligation to pay Rent on a per diem basis at the rate in effect
for the last month of the Term. Tenant shall repair damage caused by the
installation or removal of Required Removables. If Tenant fails to remove any
Required Removables or perform related repairs in a timely manner, Landlord, at
Tenant's expense, may remove and dispose of the Required Removables and perform
the required repairs. Tenant, within 30 days after receipt of an invoice, shall
reimburse Landlord for the reasonable costs incurred by Landlord.
Notwithstanding the foregoing, Tenant, at the time it requests approval for a
proposed Alteration (defined in Section IX.C), may request in writing that
Landlord advise Tenant whether the Alteration or any portion of the Alteration
will be designated as a Required Removable. Within 10 days after receipt of
Tenant's request, Landlord shall advise Tenant in writing (a "Removables
Notice") as to which portions of the Alteration, if any, will be considered to
be Required Removables. With respect to any Alteration that is the subject of a
Removables Notice, Tenant shall only be required to remove those portions, if
any, of the Alteration at the end of the Term that Landlord has indicated in the
Removables Notice will be considered a Required Removable.

IX.  Repairs and Alterations.

     A.   TENANT'S REPAIR OBLIGATIONS. In addition to Tenant's repair
          obligations pursuant to Article V hereof, Tenant shall, at its sole
          cost and expense, promptly perform all maintenance and non-structural
          repairs to the Premises that are not Landlord's express responsibility
          under this Lease, and shall keep the Premises in good condition and
          repair, reasonable wear and tear and damage by casualty or
          condemnation excepted. Tenant's repair obligations include, without
          limitation, non-structural repairs to the following located within or
          exclusively serving the Premises: (1) floor covering; (2) interior
          partitions; (3) doors; (4) the interior side of demising walls; (5)
          electronic, phone and data cabling and related equipment
          (collectively, "Cable") that is installed by or for the exclusive
          benefit of Tenant and located in the Premises or other portions of the
          Building; (6) supplemental air conditioning units, private showers and
          kitchens, including hot water heaters, plumbing, and similar
          facilities serving Tenant exclusively; and (7) Alterations performed
          by contractors retained by Tenant, including related HVAC balancing.
          All work shall be performed in accordance with the rules and
          procedures described in Section IX.C. below. If Tenant fails to make
          any repairs to the Premises for more than 15 days after notice from
          Landlord (although notice shall not be required if there is an
          emergency), Landlord may make the repairs, and Tenant shall pay the
          reasonable cost of the repairs to Landlord within 30 days after
          receipt of an invoice, together with an administrative charge in an
          amount equal to 5% of the cost of the repairs.

     B.   LANDLORD'S REPAIR OBLIGATIONS. Subject to Tenant's repair obligations
          as set forth in Article V and in Section A. above, Landlord shall keep
          and maintain in good repair and working order and make repairs to and
          perform maintenance upon: (1) structural elements of the Building and
          the Premises; (2) mechanical (including HVAC), electrical, plumbing
          and other utilities and fire/life safety systems serving the Building
          in general; (3) Common Areas; (4) the roof of the Building; (5)
          exterior windows of the Building; (6) elevators serving the Building;
          (7) exterior landscaping and grounds maintenance (including removal of
          snow and ice) and (8) if applicable, parking areas, driveways and
          walkways (collectively "Landlord Repairs"). Landlord shall promptly
          make repairs (considering the nature and urgency of the repair) for
          which Landlord is responsible.

          Landlord shall use reasonable efforts to minimize interference with
          Tenant's use and occupancy of the Premises during the performance of
          any Landlord Repairs. There shall be no Rent abatement or allowance to
          Tenant for a diminution of rental value, no actual or constructive
          eviction of Tenant, and no liability on the

                                       12
<PAGE>   15

          part of Landlord by reason of inconvenience, annoyance or injury to
          business arising from Landlord performing, or failing to perform, any
          Landlord Repairs. However, if the Premises, or a material portion of
          the Premises, is made untenantable for a period in excess of 3
          consecutive Business Days as a result of Landlord's performing, or
          failing to perform, any Landlord Repairs, then Tenant, as its sole
          remedy, shall be entitled to receive an abatement of Rent payable
          hereunder during the period beginning on the 4th consecutive Business
          Day of such untenantability and ending on the day the untenantability
          ceases. If the entire Premises has not been rendered untenantable by
          the Landlord performing, or failing to perform, any Landlord Repairs,
          the amount of abatement that Tenant is entitled to receive shall be
          prorated based upon the percentage of the Premises rendered
          untenantable and not used by Tenant. In no event, however, shall
          Landlord be liable to Tenant for any loss or damage, including the
          theft of Tenant's Property (defined in Article XV), arising out of or
          in connection with the failure of any security services, personnel or
          equipment.

     C.   ALTERATIONS. Tenant shall not make alterations, additions or
          improvements to the Premises or install any Cable in the Premises or
          other portions of the Building (collectively referred to as
          "Alterations") without first obtaining the written consent of Landlord
          in each instance, which consent shall not be unreasonably withheld or
          delayed. However, Landlord's consent shall not be required for any
          Alteration that satisfies all of the following criteria (a "Cosmetic
          Alteration"): (1) is of a cosmetic nature such as painting,
          wallpapering, hanging pictures and installing carpeting; (2) is not
          visible from the exterior of the Premises or Building; (3) will not
          affect the systems or structure of the Building; and (4) does not
          require work to be performed inside the walls or above the ceiling of
          the Premises. However, even though consent is not required, the
          performance of Cosmetic Alterations shall be subject to all the other
          provisions of this Section IX.C. Prior to starting work, Tenant shall
          furnish Landlord with plans and specifications reasonably acceptable
          to Landlord; names of contractors reasonably acceptable to Landlord
          (provided that Landlord may designate specific contractors with
          respect to Building systems); copies of contracts; necessary permits
          and approvals; evidence of contractor's and subcontractor's insurance
          in amounts reasonably required by Landlord; and any security for
          performance that is reasonably required by Landlord. Changes to the
          plans and specifications must also be submitted to Landlord for its
          approval. Alterations shall be constructed in a good and workmanlike
          manner using materials of a quality that is at least equal to the
          quality designated by Landlord as the minimum standard for the
          Building. Landlord may designate reasonable rules, regulations and
          procedures for the performance of work in the Building and, to the
          extent reasonably necessary to avoid disruption to the occupants of
          the Building, shall have the right to designate the time when
          Alterations may be performed. Tenant shall reimburse Landlord within
          30 days after receipt of an invoice for sums paid by Landlord for
          third party examination of Tenant's plans for non-Cosmetic
          Alterations. In addition, within 30 days after receipt of an invoice
          from Landlord, Tenant shall pay Landlord a fee for Landlord's
          oversight and coordination of any non-Cosmetic Alterations equal to 5%
          of the cost of the non-Cosmetic Alterations. Upon completion, Tenant
          shall furnish "as-built" plans (except for Cosmetic Alterations),
          completion affidavits, full and final waivers of lien and receipted
          bills covering all labor and materials. Tenant shall assure that the
          Alterations comply with all insurance requirements and Laws.
          Landlord's approval of an Alteration shall not be a representation by
          Landlord that the Alteration complies with applicable Laws or will be
          adequate for Tenant's use.

X.   Use of Electrical Services by Tenant.

     A.   Electricity used by Tenant in the Premises shall be paid for by Tenant
          by separate charge billed by the applicable utility company and
          payable directly by Tenant. Electrical service to the Premises may be
          furnished by one or more companies providing electrical generation,
          transmission and distribution services, and the cost of electricity
          may consist of several different components or separate charges for
          such services, such as generation, distribution and stranded cost
          charges.

                                       13
<PAGE>   16

          Landlord shall have the exclusive right to select any company
          providing electrical service to the Premises, to aggregate the
          electrical service for the Property and Premises with other buildings,
          to purchase electricity through a broker and/or buyers group and to
          change the providers and manner of purchasing electricity. Landlord
          shall be entitled to receive a fee (if permitted by Law) for the
          selection of utility companies and the negotiation and administration
          of contracts for electricity, provided that the amount of such fee
          shall not exceed 50% of any savings obtained by Landlord. For purposes
          hereof, "savings" shall mean the savings for a current year over the
          amount payable by Tenant for similar services during the previous year
          in the Lease term. By way of example, if the cost of electricity to
          the Premises during the second year of the term hereof is equal to
          $1.00 per unit consumed, and Landlord thereafter negotiates a contract
          for the provision of electricity to the Premises at a cost of $0.70
          per unit during the third year, then Landlord may charge Tenant a fee
          during the third year which shall not exceed $0.15 per unit.

     B.   Tenant's use of electrical service shall not exceed, either in
          voltage, rated capacity, use beyond Normal Business Hours or overall
          load, that which Landlord deems to be standard for the Building. If
          Tenant requests permission to consume excess electrical service,
          Landlord may reasonably refuse to consent or may condition consent
          upon conditions that Landlord reasonably elects (including, without
          limitation, the installation of utility service upgrades, meters,
          submeters, air handlers or cooling units), and the additional usage
          (to the extent permitted by Law), installation and maintenance costs
          shall be paid by Tenant. Landlord shall have the right to separately
          meter electrical usage for the Premises, at Landlord's expense, and to
          measure electrical usage by survey or other commonly accepted methods.

XI.  Entry by Landlord.

     Landlord, its agents, contractors and representatives may enter the
Premises at reasonable times to inspect or show the Premises, to clean and make
repairs, alterations or additions to the Premises, and to conduct or facilitate
repairs, alterations or additions to any portion of the Building, including
other tenants' premises. Except in emergencies or to provide janitorial and
other Building services after Normal Business Hours, Landlord shall provide
Tenant with reasonable prior notice of entry into the Premises, which may be
given orally. If reasonably necessary for the protection and safety of Tenant
and its employees, Landlord shall have the right to temporarily close all or a
portion of the Premises to perform repairs, alterations and additions. However,
except in emergencies, Landlord will not close the Premises if the work can
reasonably be completed on weekends and after Normal Business Hours, and will
use reasonable efforts to minimize any disruption to the Tenant's business in
the Premises caused by such work. Entry by Landlord shall not constitute
constructive eviction or entitle Tenant to an abatement or reduction of Rent.
Except in case of emergency, Tenant shall be entitled to have a representative
of Tenant accompany Landlord during any entry of the Premises made pursuant to
this Article XI, but the foregoing shall not be construed to require any longer
advance notice or other accommodations by Landlord beyond what is specifically
required by this Article XI.

XII. Assignment and Subletting.

     A.   Except in connection with a Permitted Transfer or a Transfer to a
          Related Corporation (both defined in Section XII.E. below), Tenant
          shall not assign, sublease, transfer or encumber any interest in this
          Lease or allow any third party to use any portion of the Premises
          (collectively or individually, a "Transfer") without the prior written
          consent of Landlord, which consent shall not be unreasonably withheld
          or delayed if Landlord does not elect to exercise its termination
          rights under Section XII.B below. Without limitation, it is agreed
          that Landlord's consent shall not be considered unreasonably withheld
          if: (1) the proposed transferee's financial condition does not meet
          the criteria Landlord uses to select Building tenants having similar
          leasehold obligations; (2) the proposed transferee's business is not
          suitable for the Building considering the business of

                                       14
<PAGE>   17

          the other tenants and the Building's prestige, or would result in a
          violation of another tenant's rights; (3) the proposed transferee is a
          governmental agency or occupant of the Building; (4) Tenant is in
          default after the expiration of the notice and cure periods in this
          Lease; or (5) any portion of the Building or Premises would likely
          become subject to additional or different Laws as a consequence of the
          proposed Transfer. Tenant shall not be entitled to receive monetary
          damages based upon a claim that Landlord unreasonably withheld its
          consent to a proposed Transfer and Tenant's sole remedy shall be an
          action to enforce any such provision through specific performance or
          declaratory judgment. Any attempted Transfer in violation of this
          Article shall, at Landlord's option, be void. Consent by Landlord to
          one or more Transfer(s) shall not operate as a waiver of Landlord's
          rights to approve any subsequent Transfers. In no event shall any
          Transfer or Permitted Transfer release or relieve Tenant from any
          obligation under this Lease.

     B.   As part of its request for Landlord's consent to a Transfer (excluding
          any Permitted Transfer or any Transfer to a Related Corportion),
          Tenant shall provide Landlord with financial statements for the
          proposed transferee, a complete copy of the proposed assignment,
          sublease and other contractual documents and such other information as
          Landlord may reasonably request. Landlord shall, by written notice to
          Tenant within 15 days of its receipt of the required information and
          documentation, either: (1) consent to the Transfer by the execution of
          a consent agreement in a form reasonably designated by Landlord or
          reasonably refuse to consent to the Transfer in writing; or (2)
          exercise its right to terminate this Lease with respect to the portion
          of the Premises that Tenant is proposing to assign or sublet. Any such
          termination shall be effective on the proposed effective date of the
          Transfer for which Tenant requested consent. Tenant shall pay Landlord
          a review fee of $2,000.00 ($750.00 if Tenant and the proposed
          transferee utilize Landlord's form of consent agreement without
          negotiation) for Landlord's review of any requested Transfer, except
          that no review fee shall be due for a Permitted Transfer or a Transfer
          to a Related Corporation.

     C.   Tenant shall pay Landlord 50% of all rent and other consideration
          which Tenant receives as a result of a Transfer that is in excess of
          the Rent payable to Landlord for the portion of the Premises and Term
          covered by the Transfer. Tenant shall pay Landlord for Landlord's
          share of any excess within 30 days after Tenant's receipt of such
          excess consideration. Tenant may deduct from the excess all reasonable
          and customary expenses directly incurred by Tenant attributable to the
          Transfer (other than Landlord's review fee), including brokerage fees,
          legal fees and construction costs. If Tenant is in Monetary Default
          (defined in Section XIX.A. below), Landlord may require that all
          sublease payments be made directly to Landlord, in which case Tenant
          shall receive a credit against Rent in the amount of any payments
          received (less Landlord's share of any excess).

     D.   Except as provided below with respect to a Permitted Transfer or a
          Transfer to a Related Corporation, if Tenant is a corporation, limited
          liability company, partnership, or similar entity, and if the entity
          which owns or controls a majority of the voting shares/rights at any
          time changes for any reason (including but not limited to a merger,
          consolidation or reorganization), such change of ownership or control
          shall constitute a Transfer. The foregoing shall not apply so long as
          Tenant is an entity whose outstanding stock is listed on a recognized
          security exchange or quotation system (including without limitation
          the NYSE, AMEX, NASDAQ National Market and NASDAQ Stock Market), or if
          at least 51% of its voting stock is owned by another entity, the
          voting stock of which is so listed.

     E.   Tenant may assign its entire interest under this Lease to a successor
          to Tenant by purchase (of either all or substantially all of Tenant's
          stock or assets), merger, consolidation or reorganization without the
          consent of Landlord, provided that all of the following conditions are
          satisfied (a "Permitted Transfer"): (1) Tenant is not in default under
          this Lease; (2) Tenant's successor shall own all or substantially all
          of the assets of Tenant; (3) Tenant's successor shall have a net worth
          which is at least equal to the greater of Tenant's net worth at the
          date of this Lease or Tenant's net worth as of the day prior to the
          proposed purchase, merger,

                                       15
<PAGE>   18

          consolidation or reorganization; (4) the Permitted Use does not allow
          the Premises to be used for retail purposes; and (5) Tenant shall give
          Landlord written notice (subject to any legal restrictions as to the
          timing of such notice) prior to the effective date of the proposed
          purchase, merger, consolidation or reorganization. Tenant's notice to
          Landlord shall include information and documentation showing that each
          of the above conditions has been satisfied. If requested by Landlord,
          Tenant's successor shall sign a commercially reasonable form of
          assumption agreement.

               Notwithstanding anything to the contrary contained herein,
          Tenant may assign its entire interest under this Lease or sublet all
          or part of the Premises to a wholly owned corporation, partnership or
          other legal entity or to any affiliate, subsidiary or parent of Tenant
          (hereinafter, collectively, referred to as "Transfer to a Related
          Corporation") without the consent of Landlord, provided: (i) Tenant is
          not in default under this Lease; (ii) such proposed transferee
          operates the business in the Premises for the Permitted Use and no
          other purpose; and (iii) in no event shall any Transfer release or
          relieve Tenant from any of its obligations under this Lease. Tenant
          shall give Landlord written notice at least thirty (30) days prior to
          the effective date of such Transfer to a Related Corporation. As used
          herein: (a) `parent' shall mean a company which owns a majority of
          Tenant's voting equity; (b) "subsidiary" shall mean a entity wholly
          owned by Tenant or at least fifty-one percent (51%) of whose voting
          equity is owned by Tenant; and (c) `affiliate' shall mean an entity
          controlled, controlling or under common control with Tenant.
          Notwithstanding the foregoing, the sale (individually or in the
          aggregate) of a majority of the shares of equity of any affiliate or
          subsidiary to which this Lease has been assigned or transferred other
          than to another parent, subsidiary or affiliate of the original Tenant
          named hereunder shall be deemed to be an assignment requiring the
          consent of Landlord hereunder. The foregoing shall not apply so long
          as Tenant is an entity whose outstanding stock is listed on a
          recognized security exchange or quotation system (including without
          limitation the NYSE, AMEX, NASDAQ National Market and NASDAQ Stock
          Market), or if at least 51% of its voting stock is owned by another
          entity, the voting stock of which is so listed

               In connection with Landlord's review of any non-public
          documents and information furnished by Tenant in connection with a
          proposed transaction with a Related Corporation, Landlord agrees to
          hold such information in confidence and not to disclose such
          information to third parties, other than its attorneys, accountants,
          prospective purchasers of the Building, partners in the Landlord
          entity and current or prospective mortgagees or the attorneys of any
          of them, or as required by law. Landlord further agrees to inform any
          such attorneys, accountants, prospective purchasers of the Building,
          partners in the Landlord entity and current or prospective mortgagees
          or the attorneys of any of them that such information is confidential.

     F.   Tenant shall be permitted to permit occupancy of part or all of the
          Premises by an entity which could be the subject of a Permitted
          Transfer or a Transfer to a Related Corporation, as defined above,
          without actually entering into a sublease or assignment with such
          entity, provided that visually, the Premises shall always appear to be
          leased to, and occupied by, a single tenant.

XIII. Liens.

     Tenant shall not permit mechanic's or other liens to be placed upon the
Property, Premises or Tenant's leasehold interest in connection with any work or
service done or purportedly done by or for benefit of Tenant. If a lien is so
placed, Tenant shall, within 10 days of notice from Landlord of the filing of
the lien, fully discharge the lien by settling the claim which resulted in the
lien or by bonding or insuring over the lien in the manner prescribed by the
applicable lien Law. If Tenant fails to discharge the lien, then, in addition to
any other right or remedy of Landlord, Landlord may bond or insure over the lien
or otherwise discharge the lien. Tenant shall reimburse Landlord for any amount
paid by Landlord to bond or insure over the lien or discharge the lien,
including, without

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<PAGE>   19

limitation, reasonable attorneys' fees (if and to the extent permitted by Law)
within 30 days after receipt of an invoice from Landlord.

XIV. Indemnity and Waiver of Claims.

     A.   Except to the extent caused by the negligence or willful misconduct of
          Landlord or any Landlord Related Parties (defined below), Tenant shall
          indemnify, defend and hold Landlord, its trustees, members,
          principals, beneficiaries, partners, officers, directors, employees,
          Mortgagee(s) (defined in Article XXVI) and agents ("Landlord Related
          Parties") harmless against and from all liabilities, obligations,
          damages, penalties, claims, actions, costs, charges and expenses,
          including, without limitation, reasonable attorneys' fees and other
          professional fees (if and to the extent permitted by Law), which may
          be imposed upon, incurred by or asserted against Landlord or any of
          the Landlord Related Parties and arising out of or in connection with
          any damage or injury occurring in the Premises or any acts or
          omissions (including violations of Law) of Tenant, the Tenant Related
          Parties (defined below) or any of Tenant's transferees, contractors or
          licensees.

     B.   Except to the extent caused by the negligence or willful misconduct of
          Tenant or any Tenant Related Parties (defined below), Landlord shall
          indemnify, defend and hold Tenant, its trustees, members, principals,
          beneficiaries, partners, officers, directors, employees and agents
          ("Tenant Related Parties") harmless against and from all liabilities,
          obligations, damages, penalties, claims, actions, costs, charges and
          expenses, including, without limitation, reasonable attorneys' fees
          and other professional fees (if and to the extent permitted by Law),
          which may be imposed upon, incurred by or asserted against Tenant or
          any of the Tenant Related Parties and arising out of or in connection
          with the acts or omissions (including violations of Law) of Landlord,
          the Landlord Related Parties or any of Landlord's contractors.

     C.   Landlord and the Landlord Related Parties shall not be liable for, and
          Tenant waives, all claims for loss or damage to Tenant's business or
          loss, theft or damage to Tenant's Property or the property of any
          person claiming by, through or under Tenant resulting from: (1) wind
          or weather; (2) the failure of any sprinkler, heating or
          air-conditioning equipment, any electric wiring or any gas, water or
          steam pipes; (3) the backing up of any sewer pipe or downspout; (4)
          the bursting, leaking or running of any tank, water closet, drain or
          other pipe; (5) water, snow or ice upon or coming through the roof,
          skylight, stairs, doorways, windows, walks or any other place upon or
          near the Building; (6) any act or omission of any party other than
          Landlord or Landlord Related Parties; and (7) any causes not
          reasonably within the control of Landlord. Tenant shall insure itself
          against such losses under Article XV below. Notwithstanding the
          foregoing, except as provided in Article XVI to the contrary, Tenant
          shall not be required to waive any claims against Landlord (other than
          for loss or damage to Tenant's business) to the extent that such loss
          or damage is due to the negligence of Landlord, the Landlord Related
          Parties, or any of Landlord's contractors. Nothing herein shall be
          construed as to diminish the repair and maintenance obligations of
          Landlord contained elsewhere in this Lease.

XV.  Insurance.

     Tenant shall carry and maintain the following insurance ("Tenant's
Insurance"), at its sole cost and expense: (1) Commercial General Liability
Insurance applicable to the Premises and its appurtenances providing, on an
occurrence basis, a minimum combined single limit of $2,000,000.00; (2) All Risk
Property/Business Interruption Insurance, including flood and earthquake,
written at replacement cost value and with a replacement cost endorsement
covering all of Tenant's trade fixtures, equipment, furniture and other personal
property within the Premises ("Tenant's Property"); (3) Workers' Compensation
Insurance as required by the state in which the Premises is located and in
amounts as may be required by applicable statute; and (4) Employers Liability
Coverage of at least $1,000,000.00 per occurrence. Any company writing any of
Tenant's Insurance shall have an A.M. Best rating of not less than A-VIII. All

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<PAGE>   20

Commercial General Liability Insurance policies shall name Tenant as a named
insured and Landlord (or any successor), Equity Office Properties Trust, a
Maryland real estate investment trust, EOP Operating Limited Partnership, a
Delaware limited partnership, and their respective members, principals,
beneficiaries, partners, officers, directors, employees, and agents, and other
designees of Landlord as the interest of such designees shall appear, as
additional insureds. All policies of Tenant's Insurance shall contain
endorsements that the insurer(s) shall give Landlord and its designees at least
30 days' advance written notice of any change, cancellation, termination or
lapse of insurance. Tenant shall provide Landlord with a certificate of
insurance evidencing Tenant's Insurance prior to the earlier to occur of the
Commencement Date or the date Tenant is provided with possession of the Premises
for any reason, and upon renewals at least 15 days prior to the expiration of
the insurance coverage. So long as the same is available at commercially
reasonable rates, Landlord shall maintain so called All Risk property insurance
on the Building at replacement cost value, as reasonably estimated by Landlord.
Except as specifically provided to the contrary, the limits of either party's
insurance shall not limit such party's liability under this Lease.

XVI. Subrogation.

     Notwithstanding anything in this Lease to the contrary, Landlord and Tenant
shall cause their respective insurance carriers to waive any and all rights of
recovery, claim, action or causes of action against the other and their
respective trustees, principals, beneficiaries, partners, officers, directors,
agents, and employees, for any loss or damage that may occur to Landlord or
Tenant or any party claiming by, through or under Landlord or Tenant, as the
case may be, with respect to Tenant's Property, the Building, the Premises, any
additions or improvements to the Building or Premises, or any contents thereof,
including all rights of recovery, claims, actions or causes of action arising
out of the negligence of Landlord or any Landlord Related Parties or the
negligence of Tenant or any Tenant Related Parties, which loss or damage is (or
would have been, had the insurance required by this Lease been carried) covered
by insurance.

XVII. Casualty Damage.

     A.   If all or any part of the Premises is damaged by fire or other
          casualty, Tenant shall immediately notify Landlord in writing. During
          any period of time that all or a material portion of the Premises is
          rendered untenantable, or if the Building is damaged such that Tenant
          is deprived of reasonable access to the Premises, as a result of a
          fire or other casualty, the Rent shall abate for the portion of the
          Premises that is untenantable or inaccessible and not used by Tenant.
          Landlord shall have the right to terminate this Lease if: (1) the
          Building shall be damaged so that, in Landlord's reasonable judgment,
          substantial alteration or reconstruction of the Building shall be
          required (whether or not the Premises has been damaged); (2) Landlord
          is not permitted by Law to rebuild the Building in substantially the
          same form as existed before the fire or casualty; (3) the Premises
          have been materially damaged and there is less than 18 months of the
          Term remaining on the date of the casualty; (4) any Mortgagee requires
          that the insurance proceeds be applied to the payment of the mortgage
          debt; or (5) a material uninsured loss to the Building occurs,
          provided that if the Premises are not damaged, Landlord may not
          terminate this Lease unless Landlord similarly terminates the leases
          of at least 50% of the other tenants in the Building. Landlord may
          exercise its right to terminate this Lease by notifying Tenant in
          writing within 90 days after the date of the casualty. If Landlord
          does not terminate this Lease, Landlord shall commence and proceed
          with reasonable diligence to repair and restore the Building and the
          Leasehold Improvements (excluding any Alterations that were performed
          by Tenant in violation of this Lease). However, in no event shall
          Landlord be required to spend more than the insurance proceeds
          received by Landlord. Landlord shall not be liable for any loss or
          damage to Tenant's Property or to the business of Tenant resulting in
          any way from the fire or other casualty or from the repair and
          restoration of the damage. Landlord and Tenant hereby waive the
          provisions of any Law relating to the matters addressed in this
          Article, and agree that their respective rights for damage to or
          destruction of the Premises shall be those specifically provided in
          this Lease.

                                       18
<PAGE>   21

     B.   If all or any portion of the Premises shall be made untenantable by
          fire or other casualty, Landlord shall, with reasonable promptness,
          cause an architect or general contractor selected by Landlord to
          provide Landlord and Tenant with a written estimate of the amount of
          time required to substantially complete the repair and restoration of
          the Premises and restore the Premises, using standard working methods,
          to substantially the condition of the Premises prior to the damage (or
          to such other condition as Tenant may proscribe which is reasonably
          acceptable to Landlord, but in no event less than restoring building
          standard installations) ("Completion Estimate"). If the Completion
          Estimate indicates that the Premises cannot be made tenantable within
          270 days from the date of such casualty, then regardless of anything
          in Section XVII.A above to the contrary, either party shall have the
          right to terminate this Lease by giving written notice to the other of
          such election within 10 days after receipt of the Completion Estimate.
          Tenant, however, shall not have the right to terminate this Lease if
          the fire or casualty was caused by the intentional misconduct of
          Tenant, Tenant Related Parties or any of Tenant's transferees,
          contractors or licensees. Notwithstanding the foregoing, if Tenant was
          entitled to but elected not to exercise its right to terminate the
          Lease and Landlord does not substantially complete the repair and
          restoration the Premises within two (2) months after the expiration of
          the estimated period of time set forth in the Completion Estimate,
          which period shall be extended to the extent of any Reconstruction
          Delays, as hereinafter defined, then Tenant may terminate this Lease
          by written notice to Landlord within fifteen (15) days after the
          expiration of such period, as the same may be extended. For purposes
          of this Lease, the term "Reconstruction Delays" shall mean: (i) any
          delays caused by the insurance adjustment process; (ii) any delays
          caused by Tenant; and (iii) any delays caused by events of Force
          Majeure.

     C.   In addition to Landlord's rights to terminate as provided herein,
          Tenant shall have the right to terminate this Lease if all of the
          following conditions occur: (1) a substantial portion of the Premises
          or the access thereto has been damaged by fire or other casualty and
          such damage cannot reasonably be repaired within sixty (60) days after
          the date of such fire or other casualty; and (2) there is less than
          one (1) year of the Lease Term remaining on the date of such casualty;
          and (3) the casualty was not caused by the negligence or willful
          misconduct of Tenant or its agents, employees or contractors; and (4)
          Tenant provides Landlord with written notice of its intent to
          terminate within thirty (30) days after the date of the fire or other
          casualty.

XVIII. Condemnation.

     Either party may terminate this Lease if the whole or any material part of
the Premises or access thereto shall be taken or condemned for any public or
quasi-public use under Law, by eminent domain or private purchase in lieu
thereof (a "Taking"). Landlord shall also have the right to terminate this Lease
if there is a Taking of any portion of the Building or Property which would
leave the remainder of the Building unsuitable for use as an office building in
a manner comparable to the Building's use prior to the Taking. In order to
exercise its right to terminate the Lease, Landlord or Tenant, as the case may
be, must provide written notice of termination to the other within 45 days after
the terminating party first receives notice of the Taking. Any such termination
shall be effective as of the date the physical taking of the Premises or the
portion of the Building or Property occurs. If this Lease is not terminated, the
Rentable Square Footage of the Building, the Rentable Square Footage of the
Premises and Tenant's Pro Rata Share shall, if applicable, be appropriately
adjusted. In addition, Rent for any portion of the Premises taken or condemned
shall be abated during the unexpired Term of this Lease effective when the
physical taking of the portion of the Premises occurs. All compensation awarded
for a Taking, or sale proceeds, shall be the property of Landlord, any right to
receive compensation or proceeds being expressly waived by Tenant. However,
Tenant may file a separate claim at its sole cost and expense for Tenant's
Property and Tenant's reasonable relocation expenses, provided the filing of the
claim does not diminish the award which would otherwise be receivable by
Landlord.

                                       19
<PAGE>   22

XIX. Events of Default.

     Tenant shall be considered to be in default of this Lease upon the
occurrence of any of the following events of default:

     A.   Tenant's failure to pay when due all or any portion of the Rent, if
          the failure continues for 5 days after written notice to Tenant
          ("Monetary Default").

     B.   Tenant's failure (other than a Monetary Default) to comply with any
          term, provision or covenant of this Lease, if the failure is not cured
          within 30 days after written notice to Tenant. However, if Tenant's
          failure to comply cannot reasonably be cured within 30 days, Tenant
          shall be allowed additional time (not to exceed 90 days) as is
          reasonably necessary to cure the failure so long as: (1) Tenant
          commences to cure the failure within 10 days, and (2) Tenant
          diligently pursues a course of action that will cure the failure and
          bring Tenant back into compliance with the Lease. However, if Tenant's
          failure to comply creates a hazardous condition, the failure must be
          cured immediately upon notice to Tenant. In addition, if Landlord
          provides Tenant with notice of Tenant's failure to comply with any
          particular term, provision or covenant of the Lease on 3 occasions
          during any 12 month period, Tenant's subsequent violation of such
          term, provision or covenant shall, at Landlord's option, be an
          incurable event of default by Tenant.

     C.   Tenant or any Guarantor becomes insolvent, makes a transfer in fraud
          of creditors or makes an assignment for the benefit of creditors, or
          admits in writing its inability to pay its debts when due.

     D.   The leasehold estate is taken by process or operation of Law.

     E    In the case of any ground floor or retail Tenant, Tenant does not take
          possession of, or abandons or vacates all or any portion of the
          Premises.

     F.   Tenant is in default beyond any notice and cure period under any other
          lease or agreement with Landlord relating to the Building which is the
          subject of this Lease or any portion thereof, including, without
          limitation, any lease or agreement for parking.

XX.  Remedies.

     A.   Upon any default, Landlord shall have the right without notice or
          demand (except as provided in Article XIX) to pursue any of its rights
          and remedies at Law or in equity, including any one or more of the
          following remedies:

          1.   Terminate this Lease, in which case Tenant shall immediately
               surrender the Premises to Landlord. If Tenant fails to surrender
               the Premises, Landlord may, in compliance with applicable Law and
               without prejudice to any other right or remedy, enter upon and
               take possession of the Premises and expel and remove Tenant,
               Tenant's Property and any party occupying all or any part of the
               Premises. Tenant shall pay Landlord on demand the amount of all
               past due Rent and other losses and damages which Landlord may
               suffer as a result of Tenant's default, whether by Landlord's
               inability to relet the Premises on satisfactory terms or
               otherwise, including, without limitation, all Costs of Reletting
               (defined below) and any deficiency that may arise from reletting
               or the failure to relet the Premises. "Costs of Reletting" shall
               include all costs and expenses incurred by Landlord in reletting
               or attempting to relet the Premises, including, without
               limitation, reasonable legal fees, brokerage commissions, the
               cost of alterations and the value of other concessions or
               allowances granted to a new tenant.

          2.   Terminate Tenant's right to possession of the Premises and, in
               compliance with applicable Law, expel and remove Tenant, Tenant's
               Property and any parties occupying all or any part of the
               Premises. Landlord may (but shall not

                                       20
<PAGE>   23

               be obligated to) relet all or any part of the Premises, without
               notice to Tenant, for a term that may be greater or less than the
               balance of the Term and on such conditions (which may include
               concessions, free rent and alterations of the Premises) and for
               such uses as Landlord in its absolute discretion shall determine.
               Landlord may collect and receive all rents and other income from
               the reletting. Tenant shall pay Landlord on demand all past due
               Rent, all Costs of Reletting and any deficiency arising from the
               reletting or failure to relet the Premises. Landlord shall not be
               responsible or liable for the failure to relet all or any part of
               the Premises or for the failure to collect any Rent. The re-entry
               or taking of possession of the Premises shall not be construed as
               an election by Landlord to terminate this Lease unless a written
               notice of termination is given to Tenant.

          3.   In lieu of calculating damages under Sections XX.A.1 or XX.A.2
               above, Landlord may elect to receive as damages the sum of (a)
               all Rent accrued through the date of termination of this Lease or
               Tenant's right to possession, and (b) an amount equal to the
               total Rent that Tenant would have been required to pay for the
               remainder of the Term discounted to present value at the Prime
               Rate (defined in Section XX.B. below) then in effect, minus the
               then present fair rental value of the Premises for the remainder
               of the Term, similarly discounted, after deducting all
               anticipated Costs of Reletting.

     B.   Unless expressly provided in this Lease, the repossession or
          re-entering of all or any part of the Premises shall not relieve
          Tenant of its liabilities and obligations under the Lease. No right or
          remedy of Landlord shall be exclusive of any other right or remedy.
          Each right and remedy shall be cumulative and in addition to any other
          right and remedy now or subsequently available to Landlord at Law or
          in equity. If Landlord declares Tenant to be in default, Landlord
          shall be entitled to receive interest on any unpaid item of Rent at a
          rate equal to the Prime Rate plus 3%. For purposes hereof, the "Prime
          Rate" shall be the per annum interest rate publicly announced as its
          prime or base rate by a federally insured bank selected by Landlord in
          the state in which the Building is located. Forbearance by Landlord to
          enforce one or more remedies shall not constitute a waiver of any
          default.

XXI. Limitation of Liability.

     NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN THIS LEASE, THE
LIABILITY OF LANDLORD (AND OF ANY SUCCESSOR LANDLORD) TO TENANT SHALL BE LIMITED
TO THE INTEREST OF LANDLORD IN THE PROPERTY. TENANT SHALL LOOK SOLELY TO
LANDLORD'S INTEREST IN THE PROPERTY FOR THE RECOVERY OF ANY JUDGMENT OR AWARD
AGAINST LANDLORD. NEITHER LANDLORD NOR ANY LANDLORD RELATED PARTY SHALL BE
PERSONALLY LIABLE FOR ANY JUDGMENT OR DEFICIENCY. BEFORE FILING SUIT FOR AN
ALLEGED DEFAULT BY LANDLORD, TENANT SHALL GIVE LANDLORD AND THE MORTGAGEE(S)
(DEFINED IN ARTICLE XXVI BELOW) WHOM TENANT HAS BEEN NOTIFIED HOLD MORTGAGES
(DEFINED IN ARTICLE XXVI BELOW) ON THE PROPERTY, BUILDING OR PREMISES, NOTICE
AND REASONABLE TIME TO CURE THE ALLEGED DEFAULT.

XXII. No Waiver.

     Either party's failure to declare a default immediately upon its
occurrence, or delay in taking action for a default shall not constitute a
waiver of the default, nor shall it constitute an estoppel. Either party's
failure to enforce its rights for a default shall not constitute a waiver of its
rights regarding any subsequent default. Receipt by Landlord of Tenant's keys to
the Premises shall not constitute an acceptance or surrender of the Premises.

XXIII. Quiet Enjoyment.

                                       21
<PAGE>   24

     Tenant shall, and may peacefully have, hold and enjoy the Premises, subject
to the terms of this Lease, provided Tenant pays the Rent and fully performs all
of its covenants and agreements. This covenant and all other covenants of
Landlord shall be binding upon Landlord and its successors only during its or
their respective periods of ownership of the Building, and shall not be a
personal covenant of Landlord or the Landlord Related Parties.

XXIV. Intentionally Omitted.

XXV. Holding Over.

     Except for any permitted occupancy by Tenant under Article VIII, if Tenant
fails to surrender the Premises at the expiration or earlier termination of this
Lease, occupancy of the Premises after the termination or expiration shall be
that of a tenancy at sufferance. Tenant's occupancy of the Premises during the
holdover shall be subject to all the terms and provisions of this Lease and
Tenant shall pay an amount (on a per month basis without reduction for partial
months during the holdover) equal to 150% of the greater of: (1) the sum of the
Base Rent and Additional Rent due for the period immediately preceding the
holdover; or (2) the fair market gross rental for the Premises as reasonably
determined by Landlord. No holdover by Tenant or payment by Tenant after the
expiration or early termination of this Lease shall be construed to extend the
Term or prevent Landlord from immediate recovery of possession of the Premises
by summary proceedings or otherwise. In addition to the payment of the amounts
provided above, if Landlord is unable to deliver possession of the Premises to a
new tenant, or to perform improvements for a new tenant, as a result of Tenant's
holdover and Tenant fails to vacate the Premises within 15 days after Landlord
notifies Tenant of Landlord's inability to deliver possession, or perform
improvements, Tenant shall be liable to Landlord for all damages, including,
without limitation, consequential damages, that Landlord suffers from the
holdover.

XXVI. Subordination to Mortgages; Estoppel Certificate.

     Landlord hereby represents that there are currently no mortgages on the
Premises, the Building, or the Property. Tenant accepts this Lease subject and
subordinate to any mortgage(s), deed(s) of trust, ground lease(s) or other
lien(s) subsequently arising upon the Premises, the Building or the Property,
and to renewals, modifications, refinancings and extensions thereof
(collectively referred to as a "Mortgage"). The party having the benefit of a
Mortgage shall be referred to as a "Mortgagee". This clause shall be
self-operative, but upon request from a Mortgagee, Tenant shall execute a
commercially reasonable subordination agreement in favor of the Mortgagee. In
lieu of having the Mortgage be superior to this Lease, a Mortgagee shall have
the right at any time to subordinate its Mortgage to this Lease. If requested by
a successor-in-interest to all or a part of Landlord's interest in the Lease,
Tenant shall, without charge, attorn to the successor-in-interest.

     Notwithstanding the foregoing, with respect to any future mortgages upon
the Building or the Property, upon written request by Tenant, Landlord will use
reasonable efforts to obtain a non-disturbance, subordination and attornment
agreement from Landlord's then current mortgagee on such mortgagee's then
current standard form of agreement. "Reasonable efforts" of Landlord shall not
require Landlord to incur any cost, expense or liability to obtain such
agreement, it being agreed that Tenant shall be responsible for any fee or
review costs charged by the mortgagee. Upon request of Landlord, Tenant will
execute the mortgagee's form of non-disturbance, subordination and attornment
agreement and return the same to Landlord for execution by the mortgagee.
Landlord's failure to obtain a non-disturbance, subordination and attornment
agreement for Tenant shall have no effect on the rights, obligations and
liabilities of Landlord and Tenant or be considered to be a default by Landlord
hereunder.

     Landlord and Tenant shall each, within 10 days after receipt of a written
request from the other, execute and deliver an estoppel certificate to those
parties as are reasonably requested by the other (including a Mortgagee or
prospective purchaser). The estoppel certificate shall include a statement
certifying that this Lease is unmodified (except as identified in the estoppel
certificate) and in full force and effect, describing the

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dates to which Rent and other charges have been paid, representing that, to such
party's actual knowledge, there is no default (or stating the nature of the
alleged default) and indicating other matters with respect to the Lease that may
reasonably be requested.

XXVII. Attorneys' Fees.

     If either party institutes a suit against the other for violation of or to
enforce any covenant or condition of this Lease, or if either party intervenes
in any suit in which the other is a party to enforce or protect its interest or
rights, the prevailing party shall be entitled to all of its reasonable costs
and expenses, including, without limitation, reasonable attorneys' fees and
expenses.

XXVIII. Notice.

     If a demand, request, approval, consent or notice (collectively referred to
as a "notice") shall or may be given to either party by the other, the notice
shall be in writing and delivered by hand or sent by registered or certified
mail with return receipt requested, or sent by overnight or same day courier
service at the party's respective Notice Address(es) set forth in Article I,
except that if Tenant has vacated the Premises (or if the Notice Address for
Tenant is other than the Premises, and Tenant has vacated such address) without
providing Landlord a new Notice Address, Landlord may serve notice in any manner
described in this Article or in any other manner permitted by Law. Each notice
shall be deemed to have been received or given on the earlier to occur of actual
delivery or the date on which delivery is refused, or, if Tenant has vacated the
Premises or the other Notice Address of Tenant without providing a new Notice
Address, three (3) days after notice is deposited in the U.S. mail or with a
courier service in the manner described above. Either party may, at any time,
change its Notice Address by giving the other party written notice of the new
address in the manner described in this Article.

XXIX. Excepted Rights.

     This Lease does not grant any rights to light or air over or about the
Building. Except as may be specifically set forth in this Lease, Landlord
excepts and reserves exclusively to itself the use of: (1) roofs, (2) telephone,
electrical and janitorial closets, (3) equipment rooms, Building risers or
similar areas that are used by Landlord for the provision of Building services,
(4) rights to the land and improvements below the floor of the Premises, (5) the
improvements and air rights above the Premises, (6) the improvements and air
rights outside the demising walls of the Premises, and (7) the areas within the
Premises used for the installation of utility lines and other installations
serving occupants of the Building. Landlord has the right to change the
Building's name or address. Landlord also has the right to make such other
changes to the Property and Building as Landlord deems appropriate, provided the
changes do not materially affect Tenant's ability to use the Premises for the
Permitted Use. Landlord shall also have the right (but not the obligation) to
temporarily close the Building if Landlord reasonably determines that there is
an imminent danger of significant damage to the Building or of personal injury
to Landlord's employees or the occupants of the Building. The circumstances
under which Landlord may temporarily close the Building shall include, without
limitation, electrical interruptions, hurricanes and civil disturbances. A
closure of the Building under such circumstances shall not constitute a
constructive eviction nor entitle Tenant to an abatement or reduction of Rent.

XXX. Surrender of Premises.

     At the expiration or earlier termination of this Lease or Tenant's right of
possession, Tenant shall remove Tenant's Property (defined in Article XV) from
the Premises, and quit and surrender the Premises to Landlord, broom clean, and
in good order, condition and repair, ordinary wear and tear and damage by
casualty or condemnation excepted. Tenant shall also be required to remove the
Required Removables in accordance with Article VIII. If Tenant fails to remove
any of Tenant's Property within 7 days after the termination of this Lease or of
Tenant's right to possession, Landlord, at Tenant's sole cost and expense, shall
be entitled (but not obligated) to remove and store Tenant's Property. Landlord
shall not be responsible for

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<PAGE>   26

the value, preservation or safekeeping of Tenant's Property. Tenant shall pay
Landlord, upon demand, the expenses and storage charges incurred for Tenant's
Property. In addition, if Tenant fails to remove Tenant's Property from the
Premises or storage, as the case may be, within 30 days after written notice,
Landlord may deem all or any part of Tenant's Property to be abandoned, and
title to Tenant's Property shall be deemed to be immediately vested in Landlord.

XXXI. Miscellaneous.

     A.   This Lease and the rights and obligations of the parties shall be
          interpreted, construed and enforced in accordance with the Laws of the
          state in which the Building is located and Landlord and Tenant hereby
          irrevocably consent to the jurisdiction and proper venue of such
          state. If any term or provision of this Lease shall to any extent be
          invalid or unenforceable, the remainder of this Lease shall not be
          affected, and each provision of this Lease shall be valid and enforced
          to the fullest extent permitted by Law. The headings and titles to the
          Articles and Sections of this Lease are for convenience only and shall
          have no effect on the interpretation of any part of the Lease.

     B.   Simultaneously with the execution of this Lease, Landlord and Tenant
          shall execute a recordable notice of lease in a form reasonably
          approved by Landlord and, upon termination for whatever reason, a like
          notice of termination of lease; and Tenant irrevocably appoints
          Landlord as its attorney-in-fact, with full power or substitution, to
          execute, acknowledge and deliver a notice of termination of lease in
          Tenant's name, place and stead if Tenant fails so to do with five (5)
          days of any request.

     C.   Landlord and Tenant hereby waive any right to trial by jury in any
          proceeding based upon a breach of this Lease.

     D.   Whenever a period of time is prescribed for the taking of an action by
          Landlord or Tenant, the period of time for the performance of such
          action shall be extended by the number of days that the performance is
          actually delayed due to strikes, acts of God, shortages of labor or
          materials, war, civil disturbances and other causes beyond the
          reasonable control of the performing party ("Force Majeure"). However,
          events of Force Majeure shall not extend any period of time for the
          payment of Rent or other sums payable by either party or any period of
          time for the written exercise of an option or right by either party.

     E.   Landlord shall have the right to transfer and assign, in whole or in
          part, all of its rights and obligations under this Lease and in the
          Building and/or Property referred to herein, and upon such transfer
          Landlord shall be released from any further obligations hereunder, and
          Tenant agrees to look solely to the successor in interest of Landlord
          for the performance of such obligations.

     F.   Tenant represents that it has dealt directly with and only with the
          Broker as a broker in connection with this Lease. Tenant shall
          indemnify and hold Landlord and the Landlord Related Parties harmless
          from all claims of any other brokers claiming to have represented
          Tenant in connection with this Lease. Landlord agrees to indemnify and
          hold Tenant and the Tenant Related Parties harmless from all claims of
          any brokers claiming to have represented Landlord in connection with
          this Lease.

     G.   Tenant covenants, warrants and represents that: (1) each individual
          executing, attesting and/or delivering this Lease on behalf of Tenant
          is authorized to do so on behalf of Tenant; (2) this Lease is binding
          upon Tenant; and (3) Tenant is duly organized and legally existing in
          the state of its organization and is qualified to do business in the
          state in which the Premises are located. If there is more than one
          Tenant, or if Tenant is comprised of more than one party or entity,
          the obligations imposed upon Tenant shall be joint and several
          obligations of all the parties and entities. Notices, payments and
          agreements given or made by, with or to any one

                                       24
<PAGE>   27

          such person or entity shall be deemed to have been given or made by,
          with and to all of them.

     H.   Time is of the essence with respect to Tenant's exercise of any
          expansion, renewal or extension rights granted to Tenant. This Lease
          shall create only the relationship of landlord and tenant between the
          parties, and not a partnership, joint venture or any other
          relationship. This Lease and the covenants and conditions in this
          Lease shall inure only to the benefit of and be binding only upon
          Landlord and Tenant and their permitted successors and assigns.

     I.   The expiration of the Term, whether by lapse of time or otherwise,
          shall not relieve either party of any obligations which accrued prior
          to or which may continue to accrue after the expiration or early
          termination of this Lease. Without limiting the scope of the prior
          sentence, it is agreed that Tenant's obligations under Sections IV.A,
          IV.B., VIII, XIV, XX, XXV and XXX shall survive the expiration or
          early termination of this Lease.

     J.   Landlord has delivered a copy of this Lease to Tenant for Tenant's
          review only, and the delivery of it does not constitute an offer to
          Tenant or an option. This Lease shall not be effective against any
          party hereto until an original copy of this Lease has been signed by
          such party.

     K.   All understandings and agreements previously made between the parties
          are superseded by this Lease, and neither party is relying upon any
          warranty, statement or representation not contained in this Lease.
          This Lease may be modified only by a written agreement signed by
          Landlord and Tenant.

XXXII. Entire Agreement.

     This Lease and the following exhibits and attachments constitute the entire
agreement between the parties and supersede all prior agreements and
understandings related to the Premises, including all lease proposals, letters
of intent and other documents: Exhibit A (Outline and Location of Premises),
Exhibit B (Rules and Regulations), Exhibit C (Commencement Letter), Exhibit D
(Work Letter Agreement, if required), Exhibit E (Additional Provisions, if
required), Exhibit F (Excluded Expenses), Exhibit G (Form of Letter of Credit)
and Exhibit H (Antenna Agreement).

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<PAGE>   28

     Landlord and Tenant have executed this Lease as of the day and year first
above written.

                        LANDLORD:
                        EOP-RIVERVIEW/245 FIRST
                        STREET, L.L.C., a Delaware
                        limited liability company company

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

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

                                   By: /s/ Thomas Bakke
                                       -----------------------------------------
                                            Vice President
                                            Hereunto Duly Authorized


                        Date Signed: June 19, 2000

                        TENANT:
                        ENGAGE TECHNOLOGIES, INC., a
                        Delaware corporation

                        By: /s/ Michael Baker
                            --------------------------------------
                        Name:Michael Baker

                        Title: V.P. and General Counsel

                        Date Signed:June 19, 2000


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