<PAGE>
 
                                                                    Exhibit 10.9
                                NOTICE OF LEASE
                                ---------------



LANDLORD:      Mortimer B. Zuckerman and Edward H. Linde, Trustees of 91
               Hartwell Avenue Trust u/d/t Trust dated September 28, 1981 and
               filed with the Middlesex South Registry District of the Land
               Court as Document 616455 as amended by instruments dated December
               10, 1984 and April 17, 1991 respectively filed with said Registry
               District as Document Nos. 675674 and 844541


TENANT:        Workgroup Technology Corporation


DATE OF
EXECUTION:     July 30, 1996


DESCRIPTION
OF PREMISES:   29,042 square feet on the third floor of the Building located at
               91 Hartwell Avenue, Lexington, Massachusetts and situated on the
               real property described in Exhibit A attached hereto.


TERM:          Sixty (60) months (plus the partial month, if any, immediately
               following the Commencement Date).


SCHEDULED TERM
COMMENCEMENT
DATE:          September 1, 1996 (as the same may be adjusted in Sections 2.4
               and 3.2 of the Lease)


RIGHTS OF RENEWAL
OR EXTENSION:  Two (2) periods of three (3) years each.
<PAGE>
 
                                                                    Exhibit 10.9
     Nothing contained herein shall be deemed to modify or amend the terms and
provisions of the Lease.

     Executed under seal this 30 day of July, 1996.

                                    LANDLORD:



                                    /s/ Edward H. Linde
                                    -----------------------------------
                                    Edward H. Linde, As Trustee and not
                                    Individually


                                    TENANT:

                                    /s/ G. R. McHorney
                                    -----------------------------------
                                    Workgroup Technology Corporation
<PAGE>
 
                                                                    Exhibit 10.9
                         COMMONWEALTH OF MASSACHUSETTS

County of Suffolk                                      July 30, 1996

     Then personally appeared the above-named Edward H. Linde, as Trustee as
aforesaid and acknowledged the foregoing instrument to be his free act and deed,
before me,


                                    --------------------------------------
                                    _______________________, Notary Public
                                    My Commission Expires:________________



                         COMMONWEALTH OF MASSACHUSETTS

County of Middlesex                                    July 30, 1996

     Then personally appeared the above-named George R. McHorney, the Vice
President & Treasurer of Workgroup Technology Corporation and acknowledged the
foregoing instrument to be the free act and deed of said Workgroup Technology
Corporation, before me,


                                    --------------------------------------
                                    _______________________, Notary Public
                                    My Commission Expires:________________
<PAGE>
 
                                                                    Exhibit 10.9

                              91 HARTWELL AVENUE
                           LEXINGTON, MASSACHUSETTS
 
                          LEASE DATED JULY  30, 1996


     THIS INSTRUMENT IS AN INDENTURE OF LEASE in which the Landlord and the
Tenant are the parties hereinafter named, and which relates to space in a
certain building (the "Building")  known as, and with an address at, 91 Hartwell
Avenue, Lexington, Massachusetts.

     The parties to this Indenture of Lease hereby agree with each other as
follows:

                                   ARTICLE I
                                   ---------
 
                                REFERENCE DATA
                                --------------

1.1  Subjects Referred To:

     Each reference in this Lease to any of the following subjects shall be
     construed to incorporate the data stated for that subject in this Article:

     LANDLORD:                      Mortimer B. Zuckerman and Edward H. Linde,
                                    Trustees of 91 Hartwell Avenue Trust under
                                    Declaration of Trust dated September 28,
                                    1981 filed with the Middlesex South Registry
                                    District as Document No. 616455 as amended
                                    by instruments dated December 10, 1984 and
                                    April 17, 1991 respectively filed with said
                                    Registry District as Document Nos. 675674
                                    and 844541 but not individually.

     LANDLORD'S ORIGINAL            
     ADDRESS:                       c/o Boston Properties, Inc.    
                                    8 Arlington Street             
                                    Boston, Massachusetts 02116    
     LANDLORD'S CONSTRUCTION                                       
     REPRESENTATIVE:                Stacey Baker                    

<PAGE>
 
                                                                    Exhibit 10.9
     TENANT:                        Workgroup Technology Corporation, a 
                                    Delaware corporation.
     TENANT'S ORIGINAL              
     ADDRESS:                       81 Hartwell Avenue             
                                    Lexington, Massachusetts 02173 
     TENANT'S CONSTRUCTION                                         
     REPRESENTATIVE:                George McHorney                 
 
     SPECIAL ALLOWANCE:             As set forth in Section 3.1 (B) hereof.
 
     SCHEDULED TERM                 
     COMMENCEMENT DATE:             September 13, 1996 
 
     COMMENCEMENT DATE:             As defined in Sections 2.4 and 3.2
 
     RENT COMMENCEMENT              
     DATE:                          The fourteenth (14th) day immediately
                                    following the Commencement Date.      
                                                                         
     OUTSIDE COMPLETION                                                  
     DATE:                          October 15, 1996                      

     ORIGINAL TERM:                 Sixty (60) calendar months (plus the partial
                                    month, if any, immediately following the
                                    Commencement Date), unless extended or
                                    sooner terminated as provided in this Lease.

     EXTENSION OPTIONS:             Two (2) periods of three (3) years each as
                                    provided in and on the terms set forth in
                                    Section 2.4.1 hereof.

     TERM OR LEASE TERM:            All references in this Lease to the Term or
                                    Lease Term shall mean the Original Term and
                                    if extended pursuant to Section 2.4.1, the
                                    Original Term as extended by the exercise of
                                    the applicable extension option(s) unless
                                    otherwise specifically provided in this
                                    Lease.

     THE SITE:                      That certain parcel of land known as and
                                    numbered 91 Hartwell Avenue, Lexington,
                                    Middlesex County, Massachusetts, being more
                                    particularly described in Exhibit A attached
                                    hereto.

     THE BUILDING:                  The Building known as and numbered 
<PAGE>
 
                                                                    Exhibit 10.9
                                    91 Hartwell Avenue, Lexington,
                                    Massachusetts. The Building is appropriately
                                    labeled on Exhibit A-1 attached hereto and
                                    hereby made a part hereof.

     THE COMPLEX:                   The Building together with all surface
                                    parking areas, the Site and all improvements
                                    (including landscaping) thereon and thereto.

     TENANT'S SPACE:                A portion of the third (3rd) floor of the
                                    Building in accordance with the floor plan
                                    attached hereto as Exhibit D and
                                    incorporated herein by reference.

     NUMBER OF PARKING SPACES:      One Hundred Five (105) spaces as same may
                                    increase pursuant to Sections 2.2 or 2.2.1
                                    hereof.

     ANNUAL FIXED RENT:             (a)    During the Original Term of this
                                           Lease at the following annual rates:

                                           (i)    For the period beginning on
                                                  the Rent Commencement Date and
                                                  continuing through the last
                                                  day of the twelfth (12th) full
                                                  calendar month of the Original
                                                  Term, at the annual rate of
                                                  $566,319.00 (being the product
                                                  of (x) $19.50 and (y) the
                                                  "Rentable Floor Area of the
                                                  Premises" (hereinafter defined
                                                  in this Section 1.1); and

                                           (ii)   For the period beginning on
                                                  the first (1st) day of the
                                                  thirteenth (13th) full
                                                  calendar month of the Original
                                                  Term and continuing through
                                                  the 
                                    
                                      -6-
<PAGE>
 
                                                                    Exhibit 10.9
                                                  last day of the twenty fourth
                                                  (24th) full calendar month of
                                                  the Original Term, at the
                                                  annual rate of $595,361.00
                                                  (being the product of (x)
                                                  $20.50 and (y) the Rentable
                                                  Floor Area of the Premises;
                                                  and

                                           (iii)  For the period beginning on
                                                  the first day of the twenty
                                                  fifth (25th) full calendar
                                                  month of the Original Term and
                                                  continuing through the last
                                                  day of the thirty sixth (36th)
                                                  full calendar month of the
                                                  Original Term, at the annual
                                                  rate of $624,403.00 (being the
                                                  product of (x) $21.50 and (y)
                                                  the Rentable Floor Area of the
                                                  Premises); and

                                           (iv)   For the period beginning on
                                                  the first day of the thirty
                                                  seventh (37th) full calendar
                                                  month of the Original Term and
                                                  continuing through the last
                                                  day of the forty eighth (48th)
                                                  full calendar month of the
                                                  Original Term, at the annual
                                                  rate of $653,445.00 (being the
                                                  product of (x) $22.50 and (y)
                                                  the Rentable Floor Area of the
                                                  Premises).

                                           (v)    For the period beginning on
                                                  the first day of the forty
                                                  ninth (49th) full calendar
                                                  month of the Original Term and

                                      -7-
<PAGE>
 
                                                                    Exhibit 10.9
                                                  continuing through the
                                                  remainder of the Original
                                                  Term, at the annual rate of
                                                  $682,487.00 (being the product
                                                  of (x) $23.50 and (y) the
                                                  Rentable Floor Area of the
                                                  Premises).

                                    (b)    During the extension option periods
                                           (if exercised), as determined
                                           pursuant to Section 2.4.1.

     OPERATING EXPENSES:            As provided in Section 2.6 hereof.

     REAL ESTATE TAXES:             As provided in Section 2.7 hereof.

     TENANT ELECTRICITY:            Initially as provided in Section 2.5 subject
                                    to adjustment as provided in Section 2.8
                                    hereof.

     ADDITIONAL RENT:               All charges and other sums payable by Tenant
                                    as set forth in this Lease, in addition to
                                    Annual Fixed Rent.

     RENTABLE FLOOR AREA            29,042 square feet.
     OF TENANT'S SPACE
     (SOMETIMES ALSO
     CALLED RENTABLE FLOOR
     AREA OF THE PREMISES):

     TOTAL RENTABLE FLOOR           122,328 square feet.
     AREA OF THE BUILDING
     (ALSO CALLED RENTABLE
     FLOOR AREA OF THE BUILDING):

     PERMITTED USES:                General office purposes.


     INITIAL MINIMUM                $2,000,000.00 combined single


                                      -8-
<PAGE>
 
                                                                    Exhibit 10.9
     LIMITS OF TENANT'S             limit per occurrence on a per location 
     COMMERCIAL GENERAL             basis.
     LIABILITY INSURANCE:

     LEGAL REQUIREMENTS:            All applicable laws, by-laws, rules,
                                    regulations, requirements, statutes and
                                    court decisions of all federal, state,
                                    county, municipal and other governmental
                                    authorities, departments, boards, agencies,
                                    commissions and other instrumentalities now
                                    or from time to time hereinafter in effect.

     INSURANCE REQUIREMENTS:        The requirements of all insurers of the
                                    Building, Site or both now or from time to
                                    time hereafter in effect.

     RECOGNIZED BROKERS:            Spaulding & Slye
                                    125 High Street
                                    Boston, Massachusetts 02110
                                           And
                                    Fallon, Hines & O'Connor, Inc.
                                    One Post Office Square
                                    Boston, Massachusetts 02109

     SECURITY DEPOSIT:              $155,375.00

1.2  Exhibits.    There are incorporated as part of this Lease:

     EXHIBIT A    Description of Site

     EXHIBIT A-1  Site Plan

     EXHIBIT B    Description of Base Building Work

     EXHIBIT B-1  Tenant's Construction Plans

     EXHIBT B-2   Tenant Extras

     EXHIBIT C    Landlord's Services

                                      -9-
<PAGE>
 
                                                                    Exhibit 10.9

     EXHIBIT D    Floor Plan

     EXHIBIT E    Form of Commencement Date
                  Agreement

     EXHIBIT F    Plan of Refusal/Offer Space

     EXHIBIT G    Broker Determination of
                  Prevailing Market Rent

     EXHIBIT H    Subordination Non-disturbance and Attornment
                  Agreement with Existing Mortgagee

1.3  Table of Articles and Sections


     ARTICLE I-REFERENCE DATA

     1.1   Subjects Referred to

     1.2   Exhibits

     1.3   Table of Articles and Sections


     ARTICLE II-THE BUILDING, PREMISES, TERM AND RENT

     2.1   The Premises

           2.1.1  Rights To Use Common Facilities

           2.1.2  Tenant's Parking

           2.1.3  Visitor Parking

           2.1.4  Rules and Regulations

     2.2   Right of First Refusal


                                     -10-
<PAGE>
 
                                                                    Exhibit 10.9

           2.2.1  Right of First Offer

     2.3   Landlord's Reservations

     2.4   Original Term

           2.4.1  Extension Options

     2.5   Monthly Fixed Rent Payments

     2.6   Adjustment for Operating Expenses

     2.7   Adjustment for Real Estate Taxes

     2.8   Adjustment for Tenant Electricity


     ARTICLE III-CONSTRUCTION

     3.1   Landlord's Construction Work

     3.2   Landlord's and Tenant's Work; Delays

     3.3   Alterations and Additions

     3.4   General Provisions Applicable to Construction


     ARTICLE IV-LANDLORD'S COVENANTS; INTERRUPTIONS AND DELAYS

     4.1   Landlord's Covenants

           4.1.1  Services Furnished by Landlord

           4.1.2  Additional Services Available to Tenant

           4.1.3  Roof, Exterior Wall, Floor Slab and Common Facility Repairs

           4.1.4  Door Signs

                                     -11-
<PAGE>
 
                                                                    Exhibit 10.9

     4.2   Interruptions and Delays in Services and Repairs, etc.

     4.3   Landlord's Insurance

     4.4   Landlord's Hazardous Materials Indemnity


     ARTICLE V-TENANT'S COVENANTS

     5.1   Payments

     5.2   Repair and Yield Up

     5.3   Use

     5.4   Obstructions; Items Visible From Exterior; Rules and Regulations

     5.5   Safety Appliances; Licenses

     5.6   Assignment; Sublease

     5.7   Tenant's Indemnity and Insurance; and Landlord's Indemnity

     5.8   Personal Property at Tenant's Risk

     5.9   Right of Entry

     5.10  Floor Load; Prevention of Vibration and Noise

     5.11  Personal Property Taxes

     5.12  Compliance with Laws

     5.13  Payment of Litigation Expenses


     ARTICLE VI-CASUALTY AND TAKING

     6.1   Fire and Casualty-Termination or Restoration; Rent Adjustment


                                     -12-
<PAGE>
 
                                                                    Exhibit 10.9

     6.2   Uninsured Casualty

     6.3   Eminent Domain-Termination or Restoration

     6.4   Eminent Domain Damages Reserved


     ARTICLE VII-DEFAULT

     7.1   Tenant's Default

     7.2   Landlord's Default


     ARTICLE VIII-MISCELLANEOUS PROVISIONS

     8.1   Extra Hazardous Use

     8.2   Waiver

     8.3   Cumulative Remedies

     8.4   Quiet Enjoyment

     8.5   Notice To Mortgagee and Ground Lessor

     8.6   Assignment of Rents

     8.7   Surrender

     8.8   Brokerage

     8.9   Invalidity of Particular Provisions

     8.10  Provisions Binding, Etc.

     8.11  Recording

     8.12  Notices


                                     -13-
<PAGE>
 
                                                                    Exhibit 10.9

     8.13  When Lease Becomes Binding

     8.14  Section Headings

     8.15  Rights of Mortgagee

     8.16  Status Report and Financial Statements

     8.17  Self-Help

     8.18  Holding Over

     8.19  Non-Subrogation

     8.20  Security Deposit

     8.21  Late Payment

     8.22  Signage

     8.23  Cafeteria

     8.24  Governing Law


                                  ARTICLE II
                                  ----------
 
                       BUILDING, PREMISES, TERM AND RENT
                       ---------------------------------

2.1  Landlord hereby demises and leases to Tenant, and Tenant hereby hires and
     accepts from Landlord, Tenant's Space in the Building excluding exterior
     faces of exterior walls, the common stairways and stairwells, elevators and
     elevator wells, fan rooms, electric and telephone closets, janitor closets,
     and pipes, ducts, conduits, wires and appurtenant fixtures serving
     exclusively, or in common, other parts of the Building, and if Tenant's
     Space includes less than the entire rentable area of any floor, excluding
     the common corridors, elevator lobbies and toilets located on such floor.

     Tenant's Space with such exclusions is hereinafter referred to as the
     "Premises". The term "Building" means the Building identified on the first
     page, and which is the subject of this Lease; the term "Site" means all,
     and also any part of the Land described in Exhibit


                                     -14-
<PAGE>
 
                                                                  Exhibit 10.9
       A, plus any additions or reductions thereto resulting from the change of
       any abutting street line and all parking areas and structures. The term
       "Property" means the Building and the Site.

2.1.1  Tenant shall have, as appurtenant to the Premises, the non-exclusive
       right to use in common with others, subject to reasonable rules and
       regulations of general applicability to tenants of the Building from time
       to time made by Landlord of which Tenant is given written notice (a) the
       common lobbies, corridors, stairways, elevators and loading area of the
       Building, and the pipes, ducts, conduits, wires and appurtenant meters
       and equipment serving the Premises in common with others, (b) common
       walkways and driveways necessary for access to the Building, (c) if the
       Premises include less than the entire rentable floor area of any floor,
       the common toilets, corridors and elevator lobby of such floor and (d)
       the cafeteria, and showers and lockers.

2.1.2  (A)  In addition, Tenant shall have the right to use the Number of
       Parking Spaces (referred to in Section 1.1) of the parking area, in
       common with use by other tenants from time to time of the Complex;
       provided, however, Landlord shall not be obligated to furnish stalls or
       spaces in any parking area specifically designated for Tenant's use.
       Landlord represents that as of the date of this Lease the total number of
       parking spaces located on the Site is not less than 427 spaces.

       (B)  Tenant covenants and agrees that it and all persons claiming by,
       through and under it, shall at all times abide by all reasonable rules
       and regulations promulgated by Landlord with respect to the use of the
       parking areas on the Site. The parking privileges granted herein are non-
       transferrable except to a permitted assignee or subtenant as provided in
       Section 5.6 through Section 5.6.6. Further, Landlord assumes no
       responsibility whatsoever for loss or damage due to fire, theft or
       otherwise to any automobile(s) parked on the Site or to any personal
       property therein, however caused, and Tenant covenants and agrees, upon
       request from Landlord from time to time, to notify its officers,
       employees, agents and invitees of such limitation of liability. Tenant
       acknowledges and agrees that a license only is hereby granted, and no
       bailment is intended or shall be created.

2.1.3  Landlord agrees to designate and appropriately mark a limited area within
       the parking area on the Site for visitor parking, the size, number of
       spaces and location of which shall be in Landlord's sole discretion. Such
       visitor parking shall be available for use by visitors to all tenants,
       subtenants and occupants of the Building (including Tenant) on a first
       come first served basis and shall not be exclusively for use by visitors
                                         --- 
       to Tenant. Tenant acknowledges and agrees that Landlord shall have no
       obligation to police the use of such visitor parking area and the use
       thereof by Tenant shall be subject to the 

                                      -15-
<PAGE>
 
                                                                  Exhibit 10.9
       conditions and requirements set forth in Section 2.1.2(B) including,
       without limitation, the applicability to Tenant and its visitors of rules
       and regulations from time to time promulgated by Landlord.

2.1.4  As of the date of this Lease, Landlord has not promulgated any such rules
       and/or any regulations under Section 2.1.1, 2.1.2 or 2.1.3. With respect
       to any such rules or regulations hereafter promulgated (which Landlord
       shall give written notice to Tenant of), Landlord shall use reasonable
       efforts to enforce such rules and regulations among the tenants in the
       Building in a non-discriminatory manner; provided, however, that failure
       to enforce such rules and regulations shall not give rise to any right of
       Tenant to terminate this Lease or to withhold, deduct or offset from or
       against Annual Fixed Rent or any Additional Rent.

2.2    (A)  This Section applies to that portion of the third (3rd) floor of the
       Building shown on Exhibit F as the "Refusal/Offer Space". Subject to the
       provisions of this Section 2.1.1, Landlord agrees that if at any time
       Landlord shall have negotiated terms with a prospective tenant upon which
       terms Landlord is prepared to enter into a letter of intent or similar
       document with said tenant respecting the leasing of all or any portion of
       the Refusal/Offer Space ("Third Party Terms"), then Landlord shall first
       give notice thereof to Tenant, provided that, as of the date Landlord
       negotiates the Third Party Terms, (i) there exists no "Event of Default"
       (as defined in Section 7.1), (ii) this Lease is still in full force and
       effect and (iii) Tenant has not assigned this Lease nor sublet more than
       twenty five percent (25%) of the Rentable Floor Area of the Premises in
       the aggregate (not including any assignment or subleasing under Section
       5.6.1). Said notice shall consist of a listing of the Third Party Terms
       and two counterpart originals of a commitment to enter into an amendment
       to this Lease to incorporate the entire space which is the subject of the
       Third Party Terms (the "Applicable Additional Space") into the Premises
       demised under this Lease upon the terms and conditions of the Third Party
       Terms; except, however, that (i) the lease term as to the Applicable
       Additional Space shall be co-terminus with the balance of the Original
       Term of this Lease; (ii) the extension options referred to in Section 1.1
       and as set forth in Section 2.4.1 shall apply to all of the premises
       leased by Tenant (that is, the original Premises leased pursuant to this
       Lease and all Applicable Additional Space from time to time leased
       pursuant to this Section 2.1.1) and (iii) the extension options must be
       exercised as to all of such premises and may not be exercised as to one
                                                    ---
       (but not all) of the original Premises or any Applicable Additional Space
       (collectively, including the Third Party Terms, the "Landlord's Submitted
       Offer"). In no event shall the Applicable Additional Space include or
       consist of more than the Refusal/Offer Space.

       (B)  Tenant shall have the right to accept Landlord's Submitted Offer by
       executing 

                                      -16-
<PAGE>
 
                                                                  Exhibit 10.9
       such two (2) counterpart original commitments to enter into such lease
       amendment and delivering to Landlord the same within five (5) business
       days after its receipt of Landlord's Submitted Offer. Within fifteen (15)
       business days after Landlord's receipt of such accepted commitment,
       Landlord shall deliver to Tenant two (2) counterpart originals of an
       amendment to this Lease to incorporate the space subject to the
       Landlord's Submitted Offer into the Premises demised under this Lease
       upon the terms and conditions of such accepted commitment. Within fifteen
       (15) business days after Tenant's receipt of such amendment Tenant shall
       execute both counterpart originals of such amendment provided that such
       amendment is reasonably acceptable to both Landlord and Tenant and shall
       deliver the same to Landlord along with appropriate evidence of the
       authority of Tenant to enter into the transaction. If Tenant shall duly
       and timely comply with the foregoing, Landlord shall execute the two (2)
       counterpart original amendments and shall promptly return one (1) fully
       executed counterpart to Tenant together with appropriate evidence of the
       authority of Landlord to enter into the transaction.

       (C)  If, at the expiration of five (5) business days after Tenant's
       receipt of Landlord's Submitted Offer, Tenant shall not have accepted
       Landlord's Submitted Offer by entering into such commitment and
       delivering the same to Landlord, or if Tenant shall so execute and
       deliver such commitment but at the end of fifteen (15) business days
       after Tenant's receipt of such lease amendment Tenant has not entered
       into such lease amendment reasonably acceptable to both parties and
       delivered the same to Landlord as set forth in subparagraph (B) above,
       time being of the essence in respect to all of the same, Landlord shall
       be free at any time thereafter to enter into a lease of the Applicable
       Additional Space subject to the Landlord's Submitted Offer with another
       prospective tenant upon terms and conditions not materially less
       favorable to Landlord than those set forth in the Third Party Terms
       provided that Landlord shall re-offer such Applicable Additional Space to
       Tenant in accordance with and subject to the terms of this Section prior
       to leasing such Applicable Additional Space upon terms materially less
       favorable to Landlord than those set forth in the Third Party Terms.

       (D)  If Tenant shall lease Applicable Additional Space pursuant to this
       Section 2.2.1, Tenant's parking rights under this Lease shall be
       increased on the basis of 3.5 parking spaces for each 1,000 square feet
       of rentable floor area of the Applicable Additional Space.

       (E)  Notwithstanding anything hereinabove set forth, this Section 2.2.1
       and Tenant's rights hereunder shall cease and expire on December 31,
       1996, time being of the essence.

2.2.1  (A)  The portion of the Refusal/Offer Space which has not been leased by
                                                             ---               
       Tenant 

                                      -17-
<PAGE>
 
                                                                  Exhibit 10.9
       pursuant to Section 2.2 is hereinafter called the "Offer Space". The
       "Existing Leases" are those leases (including, without limitation, the
       original lease terms thereof, extension options, amendments thereto but
       specifically excluding any and all expansion rights) of all or portions
       of the Offer Space entered into with tenants (the "Existing Tenants")
       upon Tenant's failure to lease space pursuant to Section 2.2. This
       Section 2.2.1 shall apply to the Offer Space but only upon the terms and
       conditions hereinafter set forth. Subject to the Existing Leases and the
       rights of the Existing Tenants thereunder, which rights are hereby made
       prior to the rights of Tenant under this Section 2.2.1, notwithstanding
       that the Existing Leases may have been executed subsequent to the date of
       this Lease, and subject to the terms of this Section 2.2.1, Landlord
       agrees not to enter into a lease or leases to relet space within the
       Offer Space without first giving to Tenant an opportunity to lease such
       space as hereinafter set forth, provided that at any time any portion of
       the Offer Space becomes so available hereunder for reletting (i) there
       exists no Event of Default, (ii) this Lease is still in full force and
       effect, (iii) Tenant has not assigned nor sublet more than twenty five
       percent (25%) of the Rentable Floor Area of the Premises in the aggregate
       (not including any assignment or subleasing under Section 5.6.1).

       (B)  When any such space becomes available for reletting upon the
       foregoing conditions, Landlord shall notify Tenant of the availability of
       such space and shall advise Tenant of the then fair market rent and
       business terms reasonably determined by Landlord upon which Landlord is
       willing so to lease such space. If Tenant wishes to exercise Tenant's
       right of first offer, Tenant shall do so, if at all, by giving Landlord
       notice of Tenant's desire to lease the entire amount of such space (it
       being agreed that Tenant has no right to lease less than the entire
       amount of the space which is so available) on such terms (reasonably
       acceptable to both Landlord and Tenant) within ten (10) business days
       after Tenant's receipt of Landlord's notice to Tenant of the availability
       of such space and of such terms. If Tenant shall give such notice, the
       same shall constitute an agreement to enter into an amendment to this
       Lease within fifteen (15) business days following Tenant's acceptance to
       incorporate such space into the Premises upon the terms set forth in
       Landlord's notice. If Tenant shall not so exercise such right within such
       period or if Tenant shall timely give an acceptance to Landlord but shall
       not enter into such an amendment to this Lease within said fifteen (15)
       business day period ( time being of the essence in respect of such
       exercise and execution), Landlord shall be free at any time thereafter to
       enter into a lease of such space with another prospective tenant upon
       terms as determined by Landlord; provided , however, that if Landlord
       shall determine to lease such space to another tenant at a rental rate
       which is materially below the then fair market rental rate, Landlord
       shall first reoffer such space to Tenant upon the terms and conditions
       determined by Landlord which shall include such then below fair market
       rental rate. Any such leases so entered into (including, but not limited
       to, the original lease terms thereof, extension options, amendments
       thereto and expansion rights) are hereinafter called the 

                                      -18-
<PAGE>
 
                                                                  Exhibit 10.9
       "Subsequent Leases" and the tenants thereunder are hereinafter called the
       "Subsequent Tenants". Subject to the Subsequent Leases and the rights of
       the Subsequent Tenants thereunder, Landlord agrees not to enter into a
       lease or leases to relet the space which is the subject of a Subsequent
       Lease without first giving Tenant an opportunity to lease such space upon
       the terms and conditions set forth in this Section 2.1.2.

       (C)  If Tenant shall exercise any such right of first offer and if,
       thereafter, the then occupant of the premises with respect to which
       Tenant shall have so exercised such right wrongfully fails to deliver
       possession of such premises at the time when its tenancy is scheduled to
       expire, Landlord shall use all reasonable efforts and due diligence
       (which shall be limited to the commencement and prosecution thereafter of
       eviction proceedings and to the payment of legal fees and other expenses
       reasonably associated with such proceedings but which shall not require
       the taking of any appeal) to evict such occupant from the Offer Space and
       to deliver possession of the Offer Space to Tenant as soon as may be
       practicable. Commencement of the term of Tenant's occupancy and lease of
       such additional space and all obligations of Tenant with respect to such
       Offer Space (including, without limitation, rental and additional rent
       obligations as to such Offer Space) shall, in the event of such holding
       over by such occupant, be deferred until possession of the additional
       space is delivered to Tenant. The failure of the then occupant of such
       premises to so vacate shall not give Tenant any right to terminate this
       Lease or to deduct from, offset against or withhold Annual Fixed Rent,
       Additional Rent or other charges due under this Lease (or any portions
       thereof) except only as specifically provided in the immediately
       preceding sentence.

       (D)  If Tenant shall lease additional space in the Building pursuant to
       this Section 2.1.2, Tenant's parking rights under this Lease shall be
       increased on the basis of 3.5 parking spaces for each 1,000 square feet
       of rentable floor area of such additional space.


2.3    Landlord reserves the right from time to time upon reasonable advance
       notice which may be given orally (except that (i) such oral notice shall
       be followed by written notice given by Landlord within three (3) business
       days thereafter and (ii) in the case of emergencies no notice shall be
       required to Tenant) and subject to Tenant's reasonably security practice
       of which Landlord is given prior notice (except in the case of
       emergencies) and without unreasonable interference with Tenant's use: (a)
       to install, use, maintain, repair, replace and relocate for service to
       the Premises and other parts of the Building, or either, pipes, ducts,
       conduits, wires and appurtenant fixtures, wherever located in the
       Premises or Building, provided that the same shall not result in a
       reduction of the Rentable Floor Area of the Premises which has a material
       and adverse affect on Tenant's use of the Premises. In the case of any
       such non-material and non-adverse reduction in the Rentable Floor 

                                      -19-
<PAGE>
 
                                                                  Exhibit 10.9
       Area of the Premises Landlord shall make a suitable adjustment thereto
       (including, without limitation, the Annual Fixed Rent and Additional
       Rent) and (b) to alter or relocate any other common facility, provided
       that substitutions are substantially equivalent or better. Installations,
       replacements and relocations referred to in clause (a) above shall be
       located so far as practicable in the central core area of the Building,
       above ceiling surfaces, below floor surfaces or within perimeter walls of
       the Premises.

2.4    Tenant shall have and hold the Premises for a period commencing on the
       earlier of (a) that date on which the Premises are "ready for occupancy"
       as that term is defined in Section 3.2 provided, or (b) that date on
       which Tenant commences occupancy of any portion of the Premises for the
       Permitted Uses (the "Commencement Date"), and continuing for the Term
       unless sooner terminated as provided in Article VI or Article VII or
       unless extended as provided in Section 2.4.1.

       As soon as may be convenient after the date has been determined on which
       the Term commences as aforesaid, Landlord and Tenant agree to join with
       each other in the execution of a written Declaration, in the form of
       Exhibit E, in which the date on which the Term commences as aforesaid and
       the Term of this Lease shall be stated. If Tenant shall fail to execute
       such Declaration, the Commencement Date and Lease Term shall be as
       reasonably determined by Landlord in accordance with the terms of this
       Lease.

2.4.1  (A)   Provided that at the time of exercise of the then applicable option
       to extend and at the commencement date of the then applicable extension
       option period (i) there exists no Event of Default (defined in Section
       7.1), (ii) this Lease is still in full force and effect, and (iii) Tenant
       has neither assigned this Lease nor sublet fifty percent (50%) or more of
       the Rentable Floor Area of the Premises in the aggregate (except for an
       assignment or subletting permitted under Section 5.6.1 hereof), Tenant
       shall have the right to extend the Term hereof upon all the same terms,
       conditions, covenants and agreements herein contained (except for the
       Annual Fixed Rent which shall be adjusted during the option periods as
       hereinbelow set forth) for two (2) successive periods of three (3) years
       each as hereinafter set forth. Each option period is sometimes herein
       referred to as an "Extended Term".

       (B)(i) If Tenant desires to exercise the then applicable option to extend
       the Term, then Tenant shall give notice to Landlord, not earlier than
       fifteen (15) months nor later than ten (10) months prior to the
       expiration of the Term as it may have been previously extended hereunder
       of Tenant's request for Landlord's quotation of a proposed annual fixed
       rent for the then applicable Extended Term. If at the expiration of
       thirty (30) days after the date when Landlord receives Tenant's written
       request as aforesaid (the "Negotiation Period"), Landlord and Tenant have
       not reached agreement on a 

                                      -20-
<PAGE>
 
                                                                  Exhibit 10.9
       determination of an annual fixed rent for the then applicable Extended
       Term and executed a written instrument extending the Term of this Lease
       pursuant to such agreement, then Tenant shall have the right, for thirty
       (30) days following the expiration of the Negotiation Period, to make a
       request to Landlord for a broker determination (the "Broker
       Determination") of the Prevailing Market Rent (as defined in Exhibit G)
       for the applicable Extended Term, which Broker Determination shall be
       made in the manner set forth in Exhibit G.

       (B)(ii) If Tenant timely shall have requested the Broker Determination,
       then in order to exercise its right to extend the Term of this Lease for
       the then applicable Extended Term, Tenant, within fifteen (15) days after
       receipt of the Broker Determination, shall give written notice to
       Landlord of Tenant's exercise of its right to extend the Lease Term for
       the then applicable Extended Term pursuant to this subsection
       2.4.1(B)(ii), in which case (x) the Annual Fixed Rent for the first
       Extended Term shall be the greater of (a) ninety five percent of the
       Prevailing Market Rent as determined by the Broker Determination for such
       Extended Term or (b) at the annual rate equal to the product of (i)
       $21.50 and (ii) the Rentable Floor Area of the Premises and (y) the
       Annual Fixed Rent for the second Extended Term shall be the greater of
       (a) ninety-five percent (95%) of the Prevailing Market Rent as determined
       by the Broker Determination for such Extended Term or (b) (i) the Annual
       Fixed Rent for the last twelve (12) months of the first Extended Term if
       the Annual Fixed Rent for such first Extended Term is fixed and constant
       or (b) (ii) the average Annual Fixed Rent during the first Extended Term
       if the Annual Fixed Rent for such first Extended Term is not fixed and
       constant. Upon the giving of notice by Tenant within said fifteen (15)
       day period as provided in this subsection (B)(ii) then this Lease and
       Lease Term hereof shall be extended for the applicable Extended Term upon
       all of the same terms, conditions, covenants and agreements contained in
       this Lease except that the Annual Fixed Rent for the applicable Extended
       Term shall be the rent determined as described in this subparagraph.

       (C)     Upon the giving of notice by Tenant to Landlord exercising
       Tenant's then applicable option to extend the Lease Term in accordance
       with the provisions of either subsection (B)(i) or (B)(ii) above, this
       Lease and the Lease Term hereof shall be extended, for the applicable
       Extended Term, without the necessity for the execution of any additional
       documents, except that Landlord and Tenant agree to enter into an
       instrument in writing setting forth the Annual Fixed Rent for the then
       applicable Extended Term but the failure to so enter into such a written
       instrument shall not negate the exercise of the applicable option to
       extend. Notwithstanding anything herein contained to the contrary, in no
       event shall Tenant have the right to exercise more than one extension
       option at a time and, further, Tenant shall not have the right to
       exercise its second extension option unless it has duly exercised its
       first extension option and in no 

                                      -21-
<PAGE>
 
                                                                  Exhibit 10.9
       event shall the Lease Term hereof be extended for more than six (6) years
       after the expiration of the Original Term hereof.

2.5    Tenant agrees to pay to Landlord, or as directed by Landlord, at
       Landlord's Original Address specified in Section 1.1 hereof, or at such
       other place as Landlord shall from time to time designate by notice in
       writing to Tenant, (1) (a) on the Rent Commencement Date (defined in
       Section 1.1 hereof) and thereafter monthly, in advance, on the first day
       of each and every calendar month during the Original Term, a sum equal to
       one twelfth (1/12th) of the applicable Annual Fixed Rent (sometimes
       hereinafter referred to as "fixed rent") and (1) (b) on the Rent
       Commencement Date and thereafter monthly, in advance, on the first day of
       each and every calendar month during the Original Term, a sum equal to
       one twelfth (1/12th) of $0.85 per annum for each square foot of Rentable
       Floor Area of Tenant's Space for tenant electricity subject to escalation
       as provided in Section 2.8 and (2) on the first day of each and every
       calendar month during each extension option period (if exercised), a sum
       equal to (a) one twelfth (1/12th) of the applicable annual fixed rent as
       determined in Section 2.4.1 for the applicable extension option period
       plus (b) then applicable monthly electricity charges (subject to
       escalation for electricity as provided in Section 2.8 hereof). Until
       written notice of some other designation is given, fixed rent and all
       other charges for which provision is herein made shall be paid by
       remittance to or for the order of Boston Properties, Inc., Agents, at 8
       Arlington Street, Boston, Massachusetts 02116, and all remittances
       received by Boston Properties, Inc., as Agents as aforesaid, or by any
       subsequently designated recipient, shall be treated as payment to
       Landlord.

       Annual Fixed Rent for any partial month shall be paid by Tenant to
       Landlord at such rate on a pro rata basis, and, if the Rent Commencement
       Date is a day other than the first day of a calendar month, the first
       payment which Tenant shall make to Landlord shall be a payment equal to a
       proportionate part of such monthly Annual Fixed Rent for the partial
       month from the Rent Commencement Date to the first day of the succeeding
       calendar month.

       Other charges payable by Tenant on a monthly basis, as hereinafter
       provided, likewise shall be prorated, and the first payment on account
       thereof shall be determined in similar fashion but shall commence on the
       Rent Commencement Date; and other provisions of this Lease calling for
       monthly payments shall be read as incorporating this undertaking by
       Tenant.

       Notwithstanding that the payment of Annual Fixed Rent and all Additional
       Rent and other charges payable by Tenant to Landlord shall not commence
       until the Rent Commencement Date, Tenant shall be subject to, and shall
       comply with, all other 

                                      -22-
<PAGE>
 
                                                                  Exhibit 10.9
       provisions of this Lease as and at the times provided in this Lease.

       The Annual Fixed Rent and all other charges for which provision is herein
       made shall be paid by Tenant to Landlord, without offset, deduction or
       abatement except as otherwise specifically set forth in this Lease.

2.6    "Landlord's Operating Expenses" means the cost of operation of the
       Building and the Site which shall exclude costs of special services
       rendered to tenants (including Tenant) for which a separate charge is
       made, but shall include, without limitation, the following: premiums for
       insurance carried with respect to the Building and the Site (including,
       without limitation, liability insurance, insurance against loss in case
       of fire or casualty and insurance of monthly installments of fixed rent
       and any Additional Rent which may be due under this Lease and other
       leases of space in the Building for not more than 12 months in the case
       of both fixed rent and Additional Rent and if there be any first mortgage
       of the Property, including such insurance as may be required by the
       holder of such first mortgage); compensation and all fringe benefits,
       workmen's compensation insurance premiums and payroll taxes paid to, for
       or with respect to all persons directly engaged in the operating,
       maintaining or cleaning of the Building or Site, water, sewer,
       electricity (for lighting of the Site, to power the heating ventilating
       and air-conditioning system and for other common areas), gas, oil and
       telephone charges (excluding utility charges separately chargeable to
       tenants for additional or special services); cost of building and
       cleaning supplies and equipment; cost of maintenance, cleaning and
       repairs (other than repairs not properly chargeable against income or
       reimbursed from contractors under guarantees); cost of snow removal and
       care of landscaping; payments under service contracts with independent
       contractors; management fees at rates competitive with other first class
       office building properties in the Route 128 West and Northwest Suburban
       Market based on and consistent with the type of occupancy and the
       services rendered; (Tenant acknowledging and agreeing to Landlord's
       current management fee rates of 3.5% of the total scheduled fixed and
       additional rents for the Building); the "Cafeteria Operating Expenses"
       (defined in Section 8.23 hereof; provided, however, that with respect to
       the Cafeteria, there shall be no duplication of expenses included in
       Operating Expenses and Cafeteria Operating Expenses, the intent being
       that a given expense with regard to the Cafeteria only be included once
       in Operating Expenses for the applicable year or other period); and all
       other reasonable and necessary expenses paid in connection with the
       operation, cleaning and maintenance of the Building and the Site and
       properly chargeable against income in accordance with generally accepted
       accounting practices as used in the real estate industry consistently
       applied, provided, however, there shall be included (a) depreciation for
       capital expenditures made by Landlord (i) to reduce operating expenses if
       Landlord shall have reasonably determined that the annual reduction in
       operating expenses shall exceed depreciation therefor or (ii) to comply
       with 

                                      -23-
<PAGE>
 
                                                                    Exhibit 10.9
       applicable Legal Requirements or Insurance Requirements; plus (b) in the
       case of both (i) and (ii) an interest factor, reasonably determined by
       Landlord, as being the interest rate then charged for long term mortgages
       by institutional lenders on like properties within the Route 128 West and
       Northwest Suburban Market; depreciation in the case of both (i) and (ii)
       shall be determined by dividing the original cost of such capital
       expenditure by the number of years of useful life of the capital item
       acquired and the useful life shall be reasonably determined by Landlord
       in accordance with generally accepted accounting principles and practices
       in effect at the time of acquisition of the capital item.

       Notwithstanding anything contained herein to the contrary, the following
       shall be excluded from Operating Expenses:

       (a)  payments of principal, interest and any other amounts related to
            mortgages or any other indebtedness encumbering all or any portion
            of the Property;

       (b)  brokerage commissions;

       (c)  wages, salaries or other compensation paid to any executive
            employees of Landlord above the grade of building manager;

       (d)  the cost of work done by Landlord for a particular tenant
            (including, without limitation, architectural, legal or engineering
            costs relating thereto);

       (e)  the initial cost of tools and equipment used in operation,
            management, repair or maintenance of the Building or Lot;

       (f)  depreciation except only as provided specifically in the preceding
            paragraph;

       (g)  costs for which Landlord, by the terms of this Lease or any other
            lease or agreement, makes a separate charge;

       (h)  ground lease rent payments;

       (i)  any unfunded reserves for future expenditures not yet incurred;

       (j)  costs of repairs or other work necessitated by fire or other
            casualty or by the exercise of eminent domain to the extent that
            Landlord is reimbursed by fire or casualty insurance or condemnation
            proceeds or to the extent such costs are covered by warranties in
            favor of Landlord.

                                      -24-
<PAGE>
 
                                                                    Exhibit 10.9
     (k)  attorneys' and other professional fees, costs and disbursements and
          other expenses incurred in connection with negotiations or disputes
          with existing or prospective tenants or other occupants of the
          Building and unrelated to the operation, maintenance, repair or
          management of the Building or Site;

     (l)  amounts paid to subsidiaries or affiliates of Landlord for services
          rendered to the Building or Site, to the extent such amounts exceed
          the competitive costs of such services rendered by other first-class
          third parties (except, however, with respect to management fees which
          shall be included as provided in the preceding paragraph;

     (m)  general overhead of Landlord and its subsidiaries and affiliates,
          except with respect to management fees which shall be as provided in
          the preceding paragraph;

     (n)  advertising and promotional expenditures;

     (o)  any fines or penalties incurred on account of violations by Landlord
          to any governmental rule or requirement, or costs incurred as the
          result of Landlord's misconduct or negligence;

     (p)  title insurance, automobile insurance, key man and other life
          insurance, long-term disability insurance and health, accident and
          sickness insurance, except only reasonable benefits to persons of the
          grade of building manager and below who are employed and engaged in
          operating and managing the Building or Site, and in the case of such
          persons engaged at more than one (1) property there shall be a
          reasonable allocation between the Property and any others;

     (q)  any expenditures for which Landlord is reimbursed by third parties

     (r)  costs and expenses incurred by Landlord in the performance of
          Landlord's obligations with respect to any environmental laws or the
          removal of hazardous substances from the Building or Site but
          specifically excluding from Landlord's obligations Tenant's obligation
          under this Lease and applicable law relating to environmental laws and
          hazardous substances;

     (s)  interest or penalties for any delinquent payments by Landlord unless
          and to the extent resulting from Tenant's failure to pay, when as due,
          the fixed rent or any Additional Rent;

                                      -25-
<PAGE>
                                                                    Exhibit 10.9
     (t)  the cost of removing or encapsulating any asbestos known to be or
          later discovered in the Building; and

     (u)  rent, additional rent or other charges under any space lease or
          sublease assumed from a tenant or subtenant of the Building.

     "Operating Expenses Allocable to the Premises" shall mean the same
     proportion of Landlord's Operating Expenses for and pertaining to the
     Building and the Site as the Rentable Floor Area of Tenant's Space bears to
     ninety five percent (95%) of the Total Rentable Floor Area of the Building.

     "Base Operating Expenses" shall mean Landlord's Operating Expenses for the
     Property for the twelve (12) month period commencing on the Commencement
     Date of this Lease and expiring on the day immediately preceding the first
     annual anniversary of the Commencement Date (herein sometimes called the
     "Base Period") subject, however, to the following provisions of this
     Section 2.6.

     "Base Operating Expenses Allocable to the Premises" shall mean the same
     proportion of Base Operating Expenses as the Rentable Floor Area of
     Tenant's Space bears to ninety five percent (95%) of the Total Rentable
     Floor Area of the Building.

     In the event that on the average less than ninety-five percent (95%) of the
     Rentable Floor Area of the Building is leased during any calendar year
     during the Lease Term (or during the Base Period for purposes of
     calculating Base Operating Expenses), Landlord's Operating Expenses for
     such calendar year or Base Period, as the case may be, shall be determined
     by Landlord to be an amount equal to the Landlord's Operating Expenses
     which would normally be expected to have been charged or incurred had
     ninety-five percent (95%) of the Rentable Floor Area of the Building been
     leased during such calendar year or Base Period, as the case may be.

     If with respect to any calendar year falling within the Term, or fraction
     of a calendar year falling within the Term at the beginning or end thereof,
     the Operating Expenses Allocable to the Premises for a full calendar year
     exceed Base Operating Expenses Allocable to the Premises or for any such
     fraction of a calendar year exceed the corresponding fraction of Base
     Operating Expenses Allocable to the Premises (such amount being hereinafter
     sometimes referred to as the "Operating Cost Excess") then Tenant shall pay
     to Landlord, as Additional Rent, the amount of such excess.  Such payments
     shall be made at the times and in the manner hereinafter provided in this
     Section 2.6.  (The Base Operating Expenses Allocable to the Premises do not
     include the $0.85 for tenant electricity to be paid by Tenant together with
     Annual Fixed Rent and for which provision is made in 

                                      -26-
<PAGE>
 
                                                                    Exhibit 10.9
     Section 2.5 hereof, separate provision being made in Section 2.8 of this
     Lease for Tenant's share of increases in electricity costs.)

     Not later than ninety (90) days after the end of the first calendar year or
     fraction thereof ending December 31 and of each succeeding calendar year
     during the Term or fraction thereof at the end of the Term, Landlord shall
     render Tenant a statement in reasonable detail together with reasonably
     supporting documentation and according to generally accepted accounting
     practices as used in the real estate industry consistently applied
     certified by a representative of Landlord, showing for the preceding
     calendar year or fraction thereof, as the case may be, Base Operating
     Expenses, Landlord's Operating Expenses and Operating Expenses Allocable to
     the Premises.  Said statement to be rendered to Tenant shall also show for
     the preceding year or fraction thereof as the case may be the amounts of
     operating expenses already paid by Tenant as Additional Rent on account of
     the operating expenses and the amount of the Operating Cost Excess
     remaining due from, or overpaid by, Tenant for the year or other period
     covered by the statement.  Within thirty (30) days after the date of
     delivery of such statement, Tenant shall pay to Landlord the balance of the
     amounts, if any, required to be paid pursuant to the above provisions of
     this Section 2.6 with respect to the preceding year or fraction thereof, or
     Landlord shall credit any amounts overpaid by Tenant against (i) monthly
     installments of fixed rent next thereafter coming due or (ii) any sums then
     due from Tenant to Landlord under this Lease (or refund such portion of the
     overpayment as aforesaid if the Term has ended and Tenant has no further
     obligation to Landlord, such refund to be made within thirty (30) days of
     such expiration or earlier termination).

     In addition, Tenant shall make payments monthly on account of Tenant's
     share of increases in operating expenses anticipated for the then current
     year at the time and in the fashion herein provided for the payment of
     fixed rent. The amount to be paid to Landlord shall be an amount reasonably
     estimated annually by Landlord to be sufficient to cover, in the aggregate,
     a sum equal to the Operating Cost Excess for each calendar year during the
     Term.

     Notwithstanding the foregoing provisions, no decrease in Landlord's
     Operating Expenses shall result in a reduction of the amount otherwise
     payable by Tenant if and to the extent said decrease is attributable to
     vacancies in the Building rather than to any other causes.

     Subject to the time period set forth in the last sentence of this paragraph
     and no more than once per any twelve (12) month period, Tenant and/or its
     auditors, accountants and representatives shall have the right, at its sole
     cost, to examine, audit and copy (at Tenant's expense) all of Landlord's
     applicable records, books, statements, bills, invoices and other materials
     evidencing the Landlord's Operating Expenses to determine whether 

                                      -27-
<PAGE>
 
                                                                    Exhibit 10.9
     Operating Expenses billed to Tenant for the immediately preceding calendar
     year conform to the foregoing provisions and requirements of this Section
     2.6. Such right shall be exercised by not less than ten (10) days written
     notice to Landlord given not later than one hundred twenty (120) days
     following Tenant's receipt of Landlord's annual statement of such charges
     (time being of the essence) (collectively the "Operating Expense
     Materials").

     If Tenant shall dispute in writing any specific item or items included in
     the yearly accounting of costs and expenses comprising Additional Rent
     provided by Landlord to Tenant pursuant to Section 2.6 or any figures or
     documentation reviewed pursuant to the foregoing paragraph (the "disputed
     expenses") and such dispute is not amicably settled between Landlord and
     Tenant by the last to occur of the following, as applicable, (i) one
     hundred twenty (120) days after such yearly accounting has been rendered to
     Tenant in the case where Tenant has not given any notice pursuant to the
     foregoing paragraph or (ii) thirty (30) days after Tenant's receipt of
     Landlord's Operating Expense Materials, pursuant to the immediately
     preceding paragraph, Tenant may, during the twenty (20) days next following
     the expiration of the applicable period  (upon written notice to Landlord
     accompanied by a copy of its letter of submission setting forth the items
     of dispute) refer such disputed item or items to arbitration in accordance
     with the following provisions of this Section (Tenant's Dispute Notice")
     and the decision rendered in such arbitration shall be conclusive and
     binding upon Landlord and Tenant.  Pending determination of any such
     dispute, the Tenant shall pay the disputed amounts in question, in
     accordance with the statement provided by Landlord, without prejudice to
     Tenant's position.  If the dispute shall be determined in Tenant's favor,
     Landlord shall promptly pay to Tenant the amount to Tenant's overpayment,
     with interest at twelve percent (12%) per annum form the date of
     overpayment until the date Landlord reimburses Tenant for same, and if no
     such payment is made by Landlord, Tenant shall be entitled to credit such
     amount against the monthly installment(s) of Rent next falling due under
     this Lease, or, if the Term has expired, such amount shall be promptly
     refunded by Landlord to Tenant. If Tenant shall not have disputed any item
     or items of any statement or accounting, Tenant shall be deemed to have
     approved such statement or accounting.

     The provisions set forth hereinbelow shall only be applicable for disputes
     arising from or out of Section 2.6 of this Lease and for no other claim,
     conflict or dispute arising from or in connection with this Lease.  If the
     Tenant demands arbitration of an item or items relating to any item or
     items of Additional Rent as set forth in Section 2.6 (the "Disputed Issue")
     Tenant shall give notice thereof to Landlord and shall in such notice
     appoint an arbitrator ("Notice of Arbitration"). Such Notice of Arbitration
     shall be given concurrently with Tenant giving Tenant's Dispute Notice to
     Landlord. Within 15 days after the Notice of Arbitration is received,
     Landlord shall by notice to Tenant appoint an

                                      -28-
<PAGE>
 
                                                                    Exhibit 10.9
     arbitrator. If the second arbitrator shall not have been appointed as
     aforesaid, the position taken Tenant shall be deemed to be the correct
     resolution of the Disputed Issue.

     Within three (3) business days after the designation of the second
     arbitrator, the two parties shall submit their respective positions with
     respect to the Disputed Issue to the two arbitrators; thereafter, the two
     arbitrators shall conduct such hearings and investigations as they may deem
     appropriate and shall, within 15 days after the designation of the second
     arbitrator, determine the correct resolution of the Disputed Issue.  The
     arbitrators or either of them shall give notice thereof (or notice of their
     inability to reach agreement, as the case may be) to the parties hereto
     within said 15 day period and the agreement, if any, of the two arbitrators
     shall be binding upon the parties hereto.

     In the event the two arbitrators are unable to reach agreement within said
     15 day period as aforesaid, the two arbitrators shall, within 30 days after
     the designation of the second arbitrator, designate a third arbitrator.  If
     the two arbitrators shall fail to agree upon the designation of such third
     arbitrator withing the 30 day period described above, then they or either
     of them shall give notice of such failure to agree to the parties hereto
     within such thirty (30) days after the arbitrators appointed by the parties
     give notice as aforesaid, then either party on behalf of both may apply to
     the president of the Greater Boston Real Estate Board, or on his or her
     failure, refusal or inability to act, to a court of competent jurisdiction,
     for the designation of such third arbitrator.

     Within three (3) business days after the designation of the third
     arbitrator, the two parties shall submit their respective positions with
     respect to the Disputed Issue to the third arbitrator; thereafter, the
     third arbitrator shall conduct such hearings and investigations as he or
     she may deem appropriate and shall, within 15 days after the date of the
     designation of the third arbitrator, determine the correct resolution of
     the Disputed Issue.  Within such 15-day period, third arbitrator shall give
     notice thereof to the parties hereto and the arbitrator's determination
     shall be binding upon the parties hereto.

     All arbitrators shall be qualified real estate professionals who shall have
     had at least ten (10) years experience managing first-class office building
     properties substantially similar to the Property in the Route 128 Boston
     West Suburban market.

     The parties shall be entitled to present evidence to the arbitrators in
     support of their respective positions.  The arbitrators may not make any
     determination inconsistent with any of the terms of this Lease.  The
     arbitrators shall not have the power to add to, modify or change any of the
     provisions of this Lease.  The determination of the arbitrator(s), as
     provided above, shall be conclusive upon the parties.  Each party shall pay
     the fees, costs 

                                      -29-
<PAGE>
 
                                                                    Exhibit 10.9
     and expenses of the arbitrator appointed by such party and the attorneys
     and expert witnesses of such party, and one-half of the other fees, costs
     and expenses of the arbitration properly incurred hereunder.

     Notwithstanding anything to the contrary contained herein, Tenant and
     Landlord shall not be precluded from utilizing the courts with respect to
     any other claim, dispute or action arising in connection with this Lease.

2.7  If with respect to any full Tax Year or fraction of a Tax Year falling
     within the Term, Landlord's Tax Expenses Allocable to the Premises (as
     hereinafter defined) for a full Tax Year exceed Base Taxes Allocable to the
     Premises or for any such fraction of a Tax Year exceed the corresponding
     fraction of Base Taxes Allocable to the Premises (such amount being
     hereinafter sometimes referred to as the "Tax Excess") then, on or before
     the thirtieth (30th) day following receipt by Tenant of the certified
     statement referred to below in this Section 2.7, Tenant shall pay to
     Landlord, as Additional Rent, the amount of the Tax Excess.  Upon request
     of Tenant, Landlord agrees to forward to Tenant a copy of the applicable
     tax bill.  Expenditures for legal fees and for other expenses incurred in
     obtaining the tax refund or abatement ("Refund/Abatement Expenses") may be
     charged against the tax refund or abatement before the adjustments are made
     for the Tax Year.  In addition, payments by Tenant on account of the Tax
     Excess anticipated for the then current year shall be made monthly at the
     time and in the fashion herein provided for the payment of fixed rent.  The
     amount so to be paid to Landlord shall be an amount reasonably estimated by
     Landlord to be sufficient to provide Landlord, in the aggregate, a sum
     equal to the Tax Excess at least ten (10) days before the day on which such
     payments by Landlord would become delinquent.  Not later than ninety (90)
     days after Landlord's Tax Expenses Allocable to the Premises are determined
     for the first such Tax Year or fraction thereof and for each succeeding Tax
     Year or fraction thereof during the Term, Landlord shall render Tenant a
     statement in reasonable detail certified by a representative of Landlord
     showing for the preceding year or fraction thereof, as the case may be,
     real estate taxes on the Building and the Site and abatements and refunds
     of any taxes and assessments and Refund/Abatement Expenses.

     To the extent that real estate taxes shall be payable to the taxing
     authority in installments with respect to periods less than a Tax Year, the
     foregoing statement shall be rendered and payments made on account of such
     installments.  Notwithstanding the foregoing provisions, no decrease in
     Landlord's Tax Expenses with respect to any Tax Year shall result in a
     reduction of the amount otherwise payable by Tenant if and to the extent
     said decrease is attributable to vacancies in the Building or partial
     completion of the Building rather than to any other causes.

                                      -30-
<PAGE>
 
                                                                    Exhibit 10.9
     Terms used herein are defined as follows:

          (i)   "Tax Year" means the twelve-month period beginning July 1 each
                year during the Term or if the appropriate governmental tax
                fiscal period shall begin on any date other than July 1, such
                other date.

          (ii)  "Landlord's Tax Expenses Allocable to the Premises" shall mean
                the same proportion of Landlord's Tax Expenses for and
                pertaining to the Building and the Site as the Rentable Floor
                Area of the Premises bears to the Total Rentable Floor Area of
                the Building.

          (iii) "Landlord's Tax Expenses" with respect to any Tax Year means the
                aggregate real estate taxes on the Building and Site with
                respect to that Tax Year, reduced by any net abatement receipts
                with respect to that Tax Year.

          (iv)  "Base Taxes" means Landlord's Tax Expenses (hereinbefore
                defined) for fiscal tax year 1996 (that is, the period beginning
                July 1, 1995 and ending June 30, 1996).

          (v)   "Base Taxes Allocable to the Premises" means the same proportion
                of Base Taxes as the Rentable Floor Area of the Premises bears
                to the Total Rentable Floor Area of the Building. As of the date
                of this Lease the Tenant's percentage is 23.741% (being the
                quotient of the Rentable Floor Area of the Premises and the
                Total Rentable Floor Area of the Building).

          (vi)  "Real estate taxes" means all taxes and special assessments of
                every kind and nature assessed by any governmental authority on
                the Building and/or Site which the Landlord shall become
                obligated to pay because of or in connection with the ownership,
                leasing and operation of the Site, the Building and the Property
                (including, without limitation, if applicable the excise
                prescribed by Mass Gen Laws Chapter 121A, Section 10 and amounts
                in excess thereof paid to the Town of Lexington pursuant to
                agreement between Landlord and the Town) and reasonable expenses
                of any proceedings for abatement of taxes. Landlord represents
                to Tenant as of the date of this Lease there is no such
                agreement in effect between Landlord and the Town of Lexington
                effecting the Premises. The amount of special taxes or special
                assessments to be included shall be limited to the amount of the
                installment (plus any interest, other than penalty interest,
                payable thereon) of such special tax or special assessment
                required to be 

                                      -31-
<PAGE>
 
                                                                    Exhibit 10.9
                paid during the year in respect of which such taxes are being
                determined. There shall be excluded from such taxes all income,
                estate, succession, inheritance, franchise and transfer taxes;
                provided, however, that if at any time during the Term the
                present system of ad valorem taxation of real property shall be
                changed so that in lieu of, or in addition to, the whole or any
                part of the ad valorem tax on real property there shall be
                assessed on Landlord a capital levy or other tax on the gross
                rents received with respect to the Site or Building or Property,
                or a federal, state, county, municipal, or other local income,
                franchise, excise or similar tax, assessment, levy or charge
                (distinct from any now in effect in the jurisdiction in which
                the Property is located) measured by or based, in whole or in
                part, upon any such gross rents, then any and all of such taxes,
                assessments, levies or charges, to the extent so measured or
                based, shall be deemed to be included within the term "real
                estate taxes" but only to the extent that the same would be
                payable if the Site and Building were the only property of
                Landlord. Landlord agrees to elect to pay betterment assessments
                over the longest period permitted by law in which case for each
                Tax Year (pro-rated for a fraction of a Tax Year) the
                installment thereof plus the interest thereon for such period
                shall be included in the calculations under this Section.

2.8  If with respect to any calendar year falling within the Term or fraction of
     a calendar year falling within the Term at the beginning or end thereof,
     the cost of furnishing electricity for lights and power to the Building for
     a full calendar year exceeds $0.85 per square foot of Rentable Floor Area
     of the Building, or for any such fraction of a calendar year exceeds the
     corresponding fraction of $0.85  per square foot of Rentable Floor Area of
     the Building, then Tenant shall pay to Landlord, as Additional Rent, on or
     before the thirtieth (30th) day following receipt by Tenant of the
     statement referred to below in this Section 2.8, its proportionate share of
     the amount of such excess (i.e. the same proportion of such excess as the
     Rentable Floor Area of Tenant's Space bears to the Total Rentable Floor
     Area of the Building).  Payments by Tenant on account of such excess shall
     be made monthly at the time and in the fashion herein provided for the
     payment of Annual Fixed Rent.  The amount so to be paid to Landlord shall
     be an amount from time to time reasonably estimated by Landlord to be
     sufficient to cover, in the aggregate, a sum equal to such excess for each
     calendar year during the Term.

     Not later than ninety (90) days after the end of the first calendar year or
     fraction thereof ending December 31 and of each succeeding calendar year
     during the Term or fraction thereof at the end of the Term, Landlord shall
     render Tenant a reasonably detailed accounting together with reasonable
     supporting documentation certified by a representative of Landlord showing
     for the preceding calendar year, or fraction thereof, as 

                                      -32-
<PAGE>
 
                                                                    Exhibit 10.9
     the case may be, the costs of furnishing electricity to the Building. Said
     statement to be rendered to Tenant also shall show for the preceding year
     or fraction thereof, as the case may be, the amount already paid by Tenant
     on account of electricity, and the amount remaining due from, or overpaid
     by, Tenant for the year or other period covered by the statement. Within
     thirty (30) days after the date of the delivery of such statement, Tenant
     shall pay to Landlord the balance of the amounts, if any required to be
     paid pursuant to the above provisions of this Section 2.8 with respect to
     the preceding year, or fraction thereof, or Landlord shall credit any
     amounts due from it to Tenant pursuant to the above provisions of this
     Section 2.8 against monthly installments of Annual Fixed Rent or Additional
     Rent next thereafter coming due unless the Lease Term has expired and
     Tenant has no other or further obligations to Landlord, in which case
     Landlord shall promptly refund such amount to Tenant.

     If at any time during the Term, or any extended term, Tenant reasonably
     concludes that the amount payable by Tenant hereunder for electricity for
     lights and power to the Premises is materially less than results from the
     above calculation, Tenant shall have the right to first give written notice
     to Landlord setting forth in reasonable detail Tenant's reasons therefor
     and Landlord and Tenant shall, in good faith, attempt to resolve such
     situation to their reasonable and mutual satisfaction.  If such a
     resolution shall not result, then Tenant shall have the right, at its sole
     cost and expense, to arrange for a study or audit of electrical usage at
     the Complex by an electrical engineer acceptable to both Landlord and
     Tenant, in the respective exercise of their reasonable judgement.  If the
     results of such study or inspection establish that the amount payment by
     Tenant is greater or lesser than the sum of the cost of electricity for
     lights and power to the Premises, the amount payable under this Section 2.8
     shall be appropriately adjusted; provided, however, that Landlord shall
     have the right to review the methodology used and results obtained by such
     engineer and to challenge the results of such study or audit.


                                  ARTICLE III
                                  -----------
 
                                 CONSTRUCTION
                                 ------------


3.1  (A) Except for the "Tenant Extras" and the "Millwork and Shelving" (both
     hereinafter referred to and all of which shall be performed in accordance
     with the requirements of Section 3.1 (B) hereof), Landlord shall perform
     the work shown on Exhibit B and Exhibit B-1 annexed hereto at Landlord's
     sole cost and expense ("Landlord's Work").  However, Landlord shall have no
     responsibility for the installation or connection of Tenant's computer,
     telephone or other communications equipment, systems or wiring.

                                      -33-
<PAGE>
 
                                                                    Exhibit 10.9
     (B) The work and items shown on and set forth in Exhibit B-2 as "Tenant
     Extras" shall be performed by Landlord at Tenant's sole cost and expense.
     During the performance of the Tenant Extras by Landlord, Landlord may
     submit, not more frequently than once every thirty (30) days and at any
     time on or after the Rent Commencement Date, an invoice setting forth in
     reasonable detail the Tenant Extras installed, performed and/or completed
     since the date of the last invoice (or in case of the first invoice or
     where no invoice has been previously sent, since the Date of this Lease)
     and within seven (7) days after receipt thereof, Tenant shall pay to
     Landlord the cost of such Tenant Extras so installed, performed and/or
     completed based on and not in excess of the amounts set forth in Exhibit 
     B-2. Final payment for the balance of the Tenant Extras shall be paid
     within ten (10) days following the last to occur of (i) Landlord's
     substantial completion of all Tenant Extras and (ii) Tenant's receipt of
     Landlord's invoice thereof.

     In addition, Landlord shall provide to Tenant a special allowance of
     $22,300.00 (the "Special Allowance") which shall be applied exclusively (i)
     to the millwork and shelving shown on Exhibit B-1 (the "Millwork and
     Shelving") or (ii) as set forth in Item No. 4 of  Exhibit B-2.  The
     Shelving and Millwork shall be performed by Tenant subject to compliance
     with the requirements of Section 3.3 hereof.

     Landlord shall provide the Special Allowance to Tenant by reimbursing
     Tenant for the Millwork and Shelving (or as set forth in Item No. 4 of
     Exhibit B-2) within ten (10) days after receipt of reasonable evidence of
     payment of the billings and invoices of Tenant's contractors and tradesmen
     but in no event shall Landlord's obligation for the cost of the Millwork
     and Shelving and the application of the Special Allowance as set forth in
     Item No. 4 of Exhibit B-2 exceed $22,300.00 in the aggregate.  The Millwork
     and Shelving (i) shall not be deemed to be or treated as part of Landlord's
     Work and (ii) shall be performed by Tenant, at its sole cost and expense,
     subject to the application of the Special Allowance by Landlord to Tenant
     as hereinabove provided.  Notwithstanding anything to the contrary
     contained in this Lease, (i) no delay in the performance of the Millwork
     and Shelving shall delay the Commencement Date and/or the Rent Commencement
     Date and the Commencement Date and/or Rent Commencement Date shall in no
     way be dependent or conditioned upon the performance of the Millwork and
     Shelving and (ii) the Millwork and Shelving shall be part of the Building
     and in no event shall it be removed or replaced.

3.2  (A)  Landlord agrees to use due diligence to complete the Landlord's Work
     described in Section 3.1 on or before the Scheduled Term Commencement Date.
     Landlord shall not be required to install any improvements which are not in
     conformity with the plans and specifications for the Building or which are
     not approved by Landlord's architect.  In case of "Tenant Delays"
     (hereinafter defined), delays due to governmental regulation, unusual

                                      -34-
<PAGE>
 
                                                                    Exhibit 10.9
     scarcity of or inability to obtain labor or materials, labor difficulties,
     casualty or other causes reasonably beyond Landlord's control
     (collectively, "Landlord's Force Majeure"), the Scheduled Term Commencement
     Date shall be extended for the period of such delays but in no event more
     than forty-five (45) days in the aggregate except in the case of Tenant
     Delays.  In no event shall Landlord's Force Majeure events exceed forty
     five (45) days in the aggregate.  The Premises shall be deemed ready for
     occupancy on the later of (a) the date on which the work described in
     Section 3.1, together with common facilities for access and service to the
     Premises, has been substantially completed except for (i) items of work and
     adjustment of equipment and fixtures which can be completed after occupancy
     thereof has been taken without causing substantial interference with
     Tenant's use of the Premises (i.e. so-called "punch list" items) and items
     of work for which there is a long lead time in obtaining the materials
     therefor or which are specially or specifically manufactured, produced or
     milled for the work in or to the Premises and require additional time for
     receipt or installation ("long lead" items) and (b) the date a certificate
     of occupancy, temporary or permanent, shall have been approved for issuance
     by applicable Governmental authority, to the extent required by law,
     permitting occupancy by Tenant of the Premises for the Permitted Use;
     provided, however, that if a temporary certificate of occupancy shall be
     issued with conditions, such conditions shall not materially and adversely
     affect Tenant's use of the Premises for the Permitted Uses.  The punch list
     shall be agreed to by both Landlord and Tenant, each acting reasonably and
     in good faith.  If there shall be issued such a temporary certificate of
     occupancy, Landlord shall satisfy the conditions set forth therein as
     promptly as possible and, in any event shall maintain the temporary
     certificate of occupancy in full force and effect until the conditions
     therein are so satisfied.  Landlord shall complete as soon as conditions
     practically permit the punch list items and the long lead items and Tenant
     shall not use the Premises in such manner as will increase the cost of
     completion.  During the performance of Landlord's Work, Tenant shall have
     reasonable access to the Premises during normal working hours for purposes
     of Tenant's performing, or causing its contractors to perform, the
     installation of its telecommunications equipment, wiring and other
     appurtenant facilities and its furniture and furnishings, provided that in
     any such case such access and work shall be performed in such manner so as
     to not cause or result in material interference with the performance of
     Landlord's Work and so as to maintain harmonious labor relations.

     For purposes hereof the term "Tenant Delay" shall mean any act or failure
     to act of Tenant or anyone employed or engaged by Tenant which may delay
     performance and/or completion of Landlord's Work.  When Landlord reasonably
     believes that any action of Tenant or failure to take action by Tenant, in
     either case by a date certain, will result in a Tenant Delay, Landlord
     shall use reasonable efforts to provide advance notice (which may be given
     orally followed up with written notice given within three (3) business
     days) 

                                      -35-
<PAGE>
 
                                                                    Exhibit 10.9
     to Tenant that such action or failure to act by such date will constitute a
     Tenant Delay. Upon the occurrence of any Tenant Delay, Landlord shall
     notify Tenant in writing within five (5) business days after the occurrence
     thereof.

     (B) Landlord at Landlord's expense, shall be responsible for Landlord's
     Work complying on the Commencement Date with the requirements of the
     Federal Americans With Disabilities Act (the "ADA") in effect on the
     Commencement Date; provided, however, that notwithstanding the foregoing,
     Tenant at Tenant's expense, shall be responsible for (i) any additions,
     alterations or improvements performed by or for Tenant or any assignee of
     subtenant of Tenant ("Tenant Improvements") complying with the ADA and (ii)
     compliance with the ADA required because of (a) Tenant Improvements and (b)
     the specific manner, conduct, intensity and method of use and deployment of
     personnel in the Premises of Tenant, any assignee of Tenant and any
     subtenant, sub-subtenant or other occupant.

     (C) If, Landlord shall have failed to substantially complete the work to be
     performed by Landlord in accordance with Section 3.1 (excluding punch list
     items and long lead items) on or before the Outside Completion Date (which
     date shall be extended automatically for such periods of time as Landlord
     is prevented from proceeding with or completing the same by reason of
     Landlord's Force Majeure or any  Tenant Delay which materially interferes
     with Landlord's construction of the Premises, without limiting Landlord's
     other rights on account thereof), Tenant shall have the right to terminate
     this Lease by giving notice to Landlord of Tenant's desire to do so within
     the time period from the Outside Completion Date (as so extended) until the
     date which is thirty (30) days subsequent to the Outside Completion Date
     (as so extended); and, upon the giving of such notice, the Term of this
     Lease shall cease and come to an end without further liability or
     obligation on the part of either party unless, within thirty (30) days
     after Landlord's receipt of Tenant's notice Landlord substantially
     completes the work to be performed by Landlord under Section 3.1 (except
     for punch list items and long lead items) and such right of termination
     shall be Tenant's sole and exclusive remedy at law or in equity or
     otherwise for Landlord's failure so to complete such work within such time.
     Tenant agrees that no Tenant Delay in performing work to prepare the
     Premises for occupancy (including, without limitation, the work in
     installing telephones and other communications equipment or systems) shall
     delay commencement of the Term or the obligation to pay rent, regardless of
     the reason for such delay or whether or not it is within the control of
     Tenant or any such employee.

3.3  This Section 3.3 shall apply before and during the Term.  Tenant shall not
     make alterations and additions to Tenant's space except in accordance with
     plans and specifications therefor first approved by Landlord, which
     approval shall not be 

                                      -36-
<PAGE>
 
                                                                    Exhibit 10.9
     unreasonably withheld. Landlord shall not be deemed unreasonable for
     withholding approval of any alterations or additions which (a) involve or
     might affect any structural or exterior element of the Building, any area
     or element outside of the Premises, or any facility serving any area of the
     Building outside of the Premises, or (b) will delay completion of the
     Premises or Building, or (c) will not comply with applicable Insurance
     Requirements, or (d) will require unusual expense to readapt the Premises
     to normal office use on Lease termination or increase the cost of
     construction or of insurance or taxes on the Building or of the services
     called for by Section 4.1 unless Tenant first gives assurance reasonably
     acceptable to Landlord for payment of such increased cost and that such
     readaptation will be made prior to such termination without expense to
     Landlord. Landlord's review and approval of any such plans and
     specifications and consent to perform work described therein shall not be
     deemed an agreement by Landlord that such plans, specifications and work
     conform with applicable Legal Requirements nor deemed a waiver of Tenant's
     obligations under this Lease with respect to applicable Legal Requirements
     nor impose any liability or obligation upon Landlord with respect to the
     completeness, design sufficiency or compliance of such plans,
     specifications and work with applicable Legal Requirements. Notwithstanding
     the foregoing, Landlord's approval shall not be required for any painting
     of the walls within the Premises (in the Building standard color) or to any
     other purely cosmetic decoration within the Premises which does not affect
     or involve any mechanical system of the Building, any other utility or
     system of the Building or any structural element of the Building. In the
     case of all alterations, additions or improvements (other than the above
     described interior painting and cosmetic work but only on the terms set
     forth above), Tenant shall deliver reasonable detailed plans and
     specifications to Landlord at the time Tenant seeks Landlord's approval.
     Landlord may elect to require Tenant to remove any alterations, additions
     or improvements upon lease expiration or termination by stating such
     election in Landlord's approval Landlord shall specify the matters for
     removal in reasonably detail. Unless specified for removal as aforesaid,
     all alterations and additions shall be part of the Building unless
     otherwise agreed upon in writing by Landlord and Tenant. All of Tenant's
     alterations and additions and installation of furnishings shall be
     coordinated with any work being performed by Landlord and in such manner
     and to the extent practicable as to maintain reasonably harmonious labor
     relations and not to damage the Building or Site or interfere with
     construction or operation of the Building and other improvements to the
     Site and, except for installation of furnishings, shall be performed by
     Landlord's general contractor or by contractors or workmen first approved
     by Landlord. Except for work by Landlord's general contractor, Tenant,
     before its work is started, shall secure all licenses and permits necessary
     therefor; deliver to Landlord a statement of the names of all its
     contractors; and other direct trades and the estimated cost of all labor
     and material to be furnished by them cause each contractor to carry
     workmen's compensation insurance in statutory amounts covering all the
     contractor's and subcontractor's employees 

                                      -37-
<PAGE>
 
                                                                    Exhibit 10.9
     and commercial general liability insurance or comprehensive general
     liability insurance with a broad form comprehensive liability endorsement
     with such limits as Landlord may reasonably require, but in no event less
     than $2,000,000.00 combined single limit per occurrence on a per location
     basis (all such insurance to be written in companies approved by Landlord
     and naming and insuring Landlord and Landlord's managing agent as
     additional insureds and insuring Tenant as well as the contractors), and to
     deliver to Landlord certificates of all such insurance. Tenant agrees to
     pay promptly when due the entire cost of any work done on the Premises by
     Tenant, its agents, employees, or independent contractors, and not to cause
     or permit any liens for labor or materials performed or furnished in
     connection therewith to attach to the Premises or the Building or the Site
     and immediately to discharge or effectively bond off any such liens which
     may so attach. Tenant shall pay, as Additional Rent, 100% of any real
     estate taxes on the Complex which shall, at any time after commencement of
     the Term, result from any alteration, addition or improvement to the
     Premises made by Tenant.

3.4  All construction work required or permitted by this Lease shall be done in
     a good and workmanlike manner using materials of good quality and in
     compliance with all applicable Legal Requirements and Insurance
     Requirements now or hereafter in force.  Each party may inspect the work of
     the other at reasonable times and shall promptly give notice of observed
     defects.  Each party authorizes the other to rely in connection with design
     and construction upon approval and other actions on the party's behalf by
     any Construction Representative of the party named in Article I or any
     person hereafter designated in substitution or addition by notice to the
     party relying.  Except as otherwise provided in Article IV, the work
     required of Landlord pursuant to this Article III shall be deemed approved
     by Tenant when Tenant commences occupancy of the Premises for the Permitted
     Uses, except for items which are then uncompleted (including punch list
     items and long lead items) and as to which Tenant shall have given notice
     to Landlord prior to such date.

     The performance of Landlord's Work hereunder shall be done in good and
     workmanlike manner employing materials of good quality and in compliance
     with applicable laws, rules, orders and regulations of governmental
     authorities having jurisdiction thereof, including, without limitation, the
     Americans with Disabilities Act ("ADA").  Landlord warrants (a) that all
     work performed by Landlord with respect to the Premises, Landlord's Work
     and all base building systems shall be free from defects (latent or
     otherwise) for the period of one (1) year commencing on the date (i) all
     such work is fully completed, or (ii) in the case of base building systems
     from the date of delivery of the Premises to Tenant as required herein, and
     (b) that the common areas of the Building and Landlord's Work in the
     Premises shall comply with the ADA and all applicable handicap access laws
     as of the Commencement Date.

                                      -38-
<PAGE>
                                                                    Exhibit 10.9
                                  ARTICLE IV
                                        
                LANDLORD'S COVENANTS; INTERRUPTIONS AND DELAYS
                ----------------------------------------------

4.1    Landlord covenants:

4.1.1  To furnish services, utilities, facilities and supplies set forth in
       Exhibit C equal to those customarily provided by landlords in high
       quality buildings in the Boston West Suburban Market subject to
       escalation reimbursement in accordance with Section 2.6.

4.1.2  To furnish, at Tenant's expense, reasonable additional Building operation
       services (beyond those set forth in Exhibit C) which are usual and
       customary in similar office buildings in the Boston West Suburban Market
       upon reasonable advance request of Tenant at reasonable and equitable
       rates from time to time established by Landlord.

4.1.3  Subject to the escalation provisions of Section 2.6 and except as
       otherwise provided in Article VI, (i) to make such repairs to the roof,
       exterior walls, floor slabs and common areas and facilities as may be
       necessary to keep them in good condition and repair and (ii) to maintain
       the Building (exclusive of Tenant's responsibilities under this Lease) in
       a first class manner comparable to the maintenance of similar properties
       in the Boston West Suburban Market.

4.1.4  To provide and install, at Landlord's expense, letters or numerals on the
       entrance doors to the Premises to identify Tenant's official name and
       Building address; all such letters and numerals shall be in the building
       standard graphics and no others shall be used or permitted on the
       Premises. In the event that Landlord shall grant to any other tenant in
       the Building the right, without the necessity of obtaining Landlord's
       consent, to affix such other tenant's corporate logo within the interior
       of such tenant's space, Landlord shall grant to Tenant a substantially
       similar right upon substantially similar terms within the interior of the
       Premises demised under this Lease. Otherwise, should Tenant desire to
       place or affix its corporate logo or name within the Premises, Tenant
       shall first seek Landlord's approval and Tenant shall submit reasonably
       detailed plans, specifications, graphics or other information with
       respect thereto Landlord shall not unreasonably withhold its consent
       thereto.

4.2  Landlord shall not be liable to Tenant for any compensation or reduction of
     rent by reason of inconvenience or annoyance or for loss of business
     arising from the necessity of Landlord or its agents entering the Premises
     for any of the purposes in this Lease 

                                     -39-
<PAGE>
                                                                    Exhibit 10.9
     authorized, or for repairing the Premises or any portion of the Building
     however the necessity may occur. In case Landlord is prevented or delayed
     from making any repairs, alterations or improvements, or furnishing any
     services or performing any other covenant or duty to be performed on
     Landlord's part, by reason of any cause reasonably beyond Landlord's
     control, including without limitation the causes set forth in Section 3.2
     hereof as being reasonably beyond Landlord's control, Landlord shall not be
     liable to Tenant therefor, nor, except as expressly otherwise provided in
     Article VI, shall Tenant be entitled to any abatement or reduction of rent
     by reason thereof. In the event that the electricity service to the
     Premises shall be shut down for more than four (4) full and consecutive
     business days, but only as a result of causes which are covered by
     Landlord's loss of rentals insurance, then Tenant shall be entitled to an
     abatement of Annual Fixed Rent equal to the "Insurance Amount" (hereinafter
     defined). The "Insurance Amount" shall be an amount equal to the payment
     actually received by Landlord (but only allocable to and on account of the
     Premises and the Annual Fixed Rent for such shut down of electricity
     service to the Premises from Landlord's insurance carrier providing such
     loss of rents insurance less the amount of any deductible contained in such
     loss of rents insurance coverage. During the Term of this Lease, Landlord
     shall carry loss of rents insurance coverage in such amounts, for such
     period (not less than one (1) year's Annual Fixed Rent) and upon such terms
     as it deems appropriate in its sole judgment. Notwithstanding anything
     herein contained to the contrary, in no event shall any of the events
     referred to in this Section 4.2 give rise to a claim in Tenant's favor that
     such failure constitutes actual or constructive, total or partial, eviction
     from the Premises.

     Landlord reserves the right to stop any service or utility system, when
     necessary by reason of accident or emergency, or until necessary repairs
     have been completed; provided, however, that in each instance of stoppage,
     Landlord shall exercise reasonable diligence to eliminate the cause
     thereof.  Except in case of emergency repairs, Landlord will give Tenant
     reasonable advance notice of any contemplated stoppage and will use
     reasonable efforts to avoid unnecessary inconvenience to Tenant by reason
     thereof.

     Landlord shall perform such maintenance, repairs and necessary replacements
     within a reasonably time after the need thereof arises and shall use
     reasonable efforts not to interfere with the Premises, or Tenant's use and
     occupancy thereof or access thereto or egress therefrom, in performing
     Landlord's obligations hereunder.  Tenant shall not be responsible for any
     repairs, damage, loss or injury to the Premises or the Building caused by
     or occasioned by Landlord's failure to repair or maintain in good repair
     those portions of the Premises or the Building set forth hereinabove or
     caused or occasioned by any act, omission, neglect, default or other
     misconduct of Landlord, its employees, agents, licenses, contractors,
     anyone claiming by, through or under Landlord or any occupant of the
     Building.

                                     -40-
<PAGE>
 
                                                                    Exhibit 10.9
4.3  During the Lease Term, Landlord shall maintain in full force a policy of
     insurance upon the Building and equipment insuring against all risks of
     physical loss or damage under an All Risk coverage endorsement in an amount
     at least equal to the full replacement value of the property insured (as
     from time to time reasonably determined by Landlord), with an Agreed Amount
     endorsement to satisfy co-insurance requirements, as well as insurance
     against breakdown of boilers and other machinery as customarily insured
     against.  Such insurance may be written with a deductible as determined by
     Landlord.  Further, if at any time during the Term all risk type insurance
     coverage shall cease to be written, then the type of fire and casualty
     insurance and amount of coverage shall be as determined by Landlord.  In
     addition, during the Lease Term, Landlord agrees to maintain in full force
     and effect with respect to the Property commercial general liability
     insurance and such other liability insurance as it shall deem reasonably
     appropriate and/or as shall be required by the holder of any mortgage
     covering the Property.  Such insurance shall be in such amounts (including
     primary and excess coverages), in such forms and upon such terms
     (including, without limitation, deductibles) as Landlord from time to time
     shall reasonably determine or as shall be required by the holder of such
     first mortgage.  Landlord may also maintain such other insurance as may
     from time to time be required by any mortgagee holding a mortgage lien on
     the Property.  In addition, Landlord may also maintain such insurance
     against  loss of Annual Fixed Rent and Additional Rent and such other risks
     and perils as Landlord deems proper.  Any and all such insurance required
     or permitted to be carried under this Lease by Landlord may be maintained
     under a blanket policy or program affecting, covering or relating to the
     Property and other properties of Landlord and/or Landlord's or Boston
     Properties Inc.'s affiliated entities or business organizations of Landlord
     and/or affiliated business organizations.  All of the insurance required or
     permitted hereunder shall be included in Landlord's Operating Costs.  Upon
     the written request of Tenant, Landlord shall furnish Tenant with copies of
     certificates or other written documentation evidencing the insurance
     carried by Landlord.

4.4  Subject to the provisions of Sections 4.2 and 8.4 hereof, Landlord shall
     hold harmless, indemnify Tenant and defend (with counsel selected by
     Landlord) with regard to any loss or liability that Tenant may actually
     incur respecting "Hazardous Materials" (defined in Section 5.3(A)) on or
     within the Property including but not limited to the reasonable and
     documented out of pocket fees and expenses of attorneys and environmental
     consultants and experts and all reasonable out of pocket costs of
     assessment, monitoring, cleanup, containment, removal and remediation
     excluding, however, punitive, indirect and consequential damages; provided,
     however, that (i) Tenant shall give prompt written notice of any such
     claim, (ii) Landlord shall have the right to handle any such claim and
     (iii) the foregoing indemnity shall not apply (a) to any acts, omissions or
     other activities of Tenant, its assignees, subtenants (including sub-
     subtenants and other occupants of the Premises or portions thereof),
     contractors, agents, servants, invitees, employees or 

                                     -41-
<PAGE>
 
                                                                 Exhibit 10.9
affiliates or (b) to any of those matters referred to in Section 5.3 hereof.


                                   ARTICLE V
                                   ---------
 
                              TENANT'S COVENANTS
                              ------------------

     Tenant covenants during the term and such further time as Tenant occupies
     any part of the Premises:

5.1  To pay when due all fixed rent and Additional Rent and all charges for
     utility services rendered to the Premises (except as otherwise provided in
     Exhibit C) and, further, as Additional Rent, all charges for additional
     services rendered pursuant to Section 4.1.2.

5.2  Except as otherwise provided in Article VI and Section 4.1.3, to keep the
     Premises in the same order, repair and condition as they were in as of the
     Commencement Date, reasonable wear and tear and damage by fire, casualty
     and eminent domain only excepted, and all glass in windows (except glass in
     exterior walls unless the damage thereto is attributable to Tenant's
     negligence or misuse) and doors of the Premises whole and in good condition
     with glass of the same type and quality as that injured or broken, damage
     by fire or taking under the power of eminent domain only excepted, and at
     the expiration or termination of this Lease peaceably to yield up the
     Premises all construction, work, improvements, and all alterations and
     additions thereto in the same order, repair and condition as they were in
     as of the Commencement Date, reasonable wear and tear and damage by fire,
     casualty and eminent domain only excepted, first removing all goods and
     effects of Tenant and, to the extent specified by Landlord by notice to
     Tenant given at least twenty (20) days before such expiration or
     termination, the wiring for Tenant's computer, telephone and other
     communication systems and equipment and repairing any damage caused by such
     removal and restoring the Premises and leaving them clean and neat.  Tenant
     shall not permit or commit any waste, and Tenant shall be responsible for
     the cost of repairs which are necessary by reason of damage to common areas
     in the Building or to the Site caused by Tenant, Tenant's independent
     contractors, Tenant's employees or Tenant's invitees.  Notwithstanding
     anything contained in this Lease to the contrary, the following shall be
     deemed to be Tenant Trade Fixtures for purposes of this Lease, shall remain
     the property of the Tenant and may, at Tenant's option, be removed by
     Tenant at any time prior to or upon the expiration of this Lease, provided
     that Tenant shall, at its expense, repair any damage to the Premises caused
     by any such installation or removal:  All audio/projection/visual/multi-
     media equipment located in the Premises at any time during the Term 
     hereof or any extended term.

                                      42
<PAGE>
 
                                                                 Exhibit 10.9
5.3  From the commencement of the Term, to use and occupy the Premises (subject
     to the provisions of Sections 5.6 through 5.6.6 hereof) for the Permitted
     Uses only, and not to injure or deface the Premises, Building, the Site or
     any other part of the Complex nor to permit in the Premises or on the Site
     any auction sale, vending machine  (except as set forth below), or
     inflammable fluids or chemicals (except in deminimous amounts and types
     customarily used in conjunction with normal office purposes, tenant
     covenanting and agreeing to comply with (a) all laws, by-laws, rules and
     regulations applicable to the same including, without limitation, those
     hereinafter set forth in this Section 5.3 and (b) the following
     requirements of this Section 5.3), or nuisance, or the emission from the
     Premises of any objectionable noise or odor, nor to use or devote the
     Premises or any part thereof for any purpose other than the Permitted Uses,
     nor for any use thereof which is inconsistent with maintaining the Building
     as a first class office building in the quality of its maintenance, use and
     occupancy, or which is improper, or contrary to applicable law, by-law,
     rule or regulation or liable to render necessary any alteration or addition
     to the Building.  Notwithstanding the foregoing respecting vending
     machines, Tenant may, at its sole cost, expense and risk, keep a reasonable
     number of vending machines in the Premises dispensing non-alcoholic
     beverages, candy and other food products and sundries, Tenant covenanting
     that Tenant shall be solely responsible for compliance with applicable
     laws, by-laws, rules and regulations, obtaining all permits, licenses and
     approvals thereof, and maintaining same in full force and effect. Further,
     (i) Tenant shall not, nor shall Tenant permit its employees, invitees,
     agents, independent contractors, contractors, assignees or subtenants to,
     keep, maintain, store or dispose of (into the sewage or waste disposal
     system or otherwise) or engage in any activity which might produce or
     generate any substance which is or may hereafter be classified as a
     hazardous material, waste or substance (collectively "Hazardous
     Materials"), under federal, state or local laws, rules and regulations,
     including, without limitation, 42 U.S.C. Section 6901 et seq., 42 U.S.C.
     Section 9601 et seq., 42 U.S.C. Section 2601 et seq., 49 U.S.C. Section
     1802 et seq. and Massachusetts General Laws, Chapter 21E and the rules and
     regulations promulgated under any of the foregoing, as such laws, rules and
     regulations may be amended from time to time (collectively "Hazardous
     Materials Laws"), (ii) Tenant shall promptly notify Landlord of any
     incident in, on or about the Premises, the Building or the Site that would
     require the filing of a notice under any Hazardous Materials Laws, (iii)
     Tenant shall comply and shall cause its employees, invitees, agents,
     independent contractors,  contractors, assignees and subtenants to comply
     with each of the foregoing and (iv) Landlord shall have the right to make
     such inspections (including testing) as Landlord shall elect from time to
     time to determine that Tenant is complying with the foregoing; provided
     that all such inspections shall be at Landlord's sole cost and expense
     (unless there shall be a violation by Tenant or any others hereinabove set
     forth of Hazardous Materials Laws in which case such inspection shall be at
     Tenant's sole cost and expense) and Landlord shall be entitled to access
     the Premises for such inspections 

                                      43
<PAGE>
                                                                    Exhibit 10.9
       provided Landlord gives Tenant reasonable advance notice of same (orally
       or in writing with any oral notice followed within three (3) business
       days by written notice) except in the case of emergencies and except in
       the case of emergencies such access (i) shall be subject to Tenant's
       reasonable security practices and (ii) shall be performed in such a
       manner as to reasonably minimize the interruption of Tenant's business
       operations.

5.4    Not to obstruct in any manner any portion of the Building not hereby
       leased or any portion thereof or of the Site used by Tenant in common
       with others; not without prior consent of Landlord to permit the painting
       or placing of any signs, curtains, blinds, shades, awnings, aerials or
       flagpoles, or the like, visible from outside the Premises; and to comply
       with all reasonable Rules and Regulations now or hereafter made by
       Landlord, of which Tenant has been given written notice, for the care and
       use of the Building and Site and their facilities and approaches;
       Landlord shall not be liable to Tenant for the failure of other occupants
       of the Building to conform to such Rules and Regulations. As of the date
       hereof, there are no such rules and/or regulations in effect.

5.5    To keep the Premises equipped with all safety appliances required by any
       public authority because of any use made by Tenant other than normal
       office use, and to procure all licenses and permits so required because
       of such use and, if requested by Landlord, to do any work to the Premises
       so required because of such use, it being understood that the foregoing
       provisions shall not be construed to broaden in any way Tenant's
       Permitted Uses.

5.6    Except as otherwise expressly provided herein, Tenant covenants and
       agrees that it shall not assign, mortgage, pledge, hypothecate or
       otherwise transfer this Lease and/or Tenant's interest in this Lease or
       sublet (which term, without limitation, shall include granting of
       concessions, licenses or the like) the whole or any part of the Premises.
       Any assignment, mortgage, pledge, hypothecation, transfer or subletting
       not expressly permitted in or consented to by Landlord under Sections
       5.6.1-5.6.6 shall be void, ab initio; shall be of no force and effect;
       and shall confer no rights on or in favor of third parties. In addition,
       Landlord shall be entitled to seek specific performance of or other
       equitable relief with respect to the provisions hereof.

5.6.1  Notwithstanding the provisions of Section 5.6 above and the provisions of
       Section 5.6.2, 5.6.3 and 5.6.5 below, Tenant shall have the right to
       assign this Lease or to sublet the Premises (in whole or in part) to any
       parent or subsidiary corporation of Tenant or to any corporation into
       which Tenant may be converted or with which it may merge, provided that
       the entity to which this Lease is so assigned or which so sublets the
       Premises has a financial liquidity and capability and credit worthiness
       to perform the obligations of the Tenant under this Lease as and when due
       and required. Any such assignment or 

                                      44
<PAGE>
                                                                    Exhibit 10.9
       subletting shall be subject to the provisions of Section 5.6.4 and
       Section 5.6.6 below.

5.6.2  Notwithstanding the provisions of Section 5.6 above, in the event Tenant
       desires to assign this Lease or to sublet the Premises in whole or in
       part, Tenant shall notify Landlord thereof in writing and Landlord shall
       have the right at its sole option, to be exercised within the time period
       set forth in Section 5.6.4 to:

            (i)   In the case of a proposed assignment of the Lease or
                  subletting of the entire Premises, Landlord may, at its sole
                  option, elect to terminate this Lease as of a date specified
                  in a notice to Tenant, which date shall not be earlier than
                  sixty (60) days nor later than one hundred twenty (120) days
                  after Landlord's notice to Tenant; provided, however, that
                  upon the termination date as set forth in Landlord's notice,
                  all obligations relating to the period after such termination
                  date (but not those relating to the period before such
                  termination date) shall cease and promptly upon being billed
                  therefor by Landlord, Tenant shall make final payment of all
                  rent and Additional Rent due from Tenant through the
                  termination date.

            (ii)  In the case of a proposed subleasing of more than fifty
                  percent (50%) but less than the entire Premises, Landlord may,
                  at its sole option, elect to terminate this Lease as to such
                  portion of the Premises proposed to be sublet (herein called
                  the "Terminated Portion of the Premises") as of a date which
                  shall be not earlier than sixty (60) days nor later than one
                  hundred twenty (120) days after Landlord's notice to Tenant;
                  provided, however, that upon the termination date as set forth
                  in Landlord's notice, all of Landlord's and Tenant's
                  obligations as to the Terminated Portion of the Premises
                  relating to the period after such termination date (but not
                  those relating to the period before such termination date)
                  shall cease and promptly upon being billed therefor by
                  Landlord, Tenant shall make final payment of all rent and
                  Additional Rent due from Tenant respecting the Terminated
                  Portion of the Premises through the termination date and
                  provided, further, that this Lease shall remain in full force
                  and effect as to the remainder of the Premises, except that
                  from and after the termination date the Rentable Floor Area of
                  the Premises shall be reduced to the rentable floor area of
                  the remainder of the Premises and the definition of Rentable
                  Floor Area of the Premises shall be so amended and after such
                  termination all references in this Lease to the "Premises" or
                  the "Rentable Floor Area of the Premises" shall be deemed to
                  be references to the remainder of the Premises, and provided
                  further that Landlord shall have the right to make such
                  alterations and improvements as may be required to 

                                      45
<PAGE>
                                                                    Exhibit 10.9
                  separately demise the Terminated Portion of the Premises. In
                  addition, from and after the effective date of any such
                  termination, Annual Fixed Rent shall be at the rate set forth
                  in Section 1.1 but shall be calculated using the rentable
                  floor area of the remainder of the Premises and Tenant's
                  payments for operating costs, real estate taxes and
                  electricity shall be calculated on the same basis set forth in
                  this Lease using the rentable floor area of the remainder of
                  the Premises.

            (iii) In the event that Landlord shall not exercise its termination
                  rights as aforesaid, or shall fail to give any or timely
                  notice under subsection (i) or subsection (ii) immediately
                  above, the provisions of Sections 5.6.3-5.6.6 shall be
                  applicable. This Section 5.6.2 shall not be applicable to an
                  assignment or sublease pursuant to Section 5.6.1.

5.6.3  Notwithstanding the provisions of Section 5.6 above, but subject to the
                                                            ---               
       provisions of this Section 5.6.3 and the provisions of Sections 5.6.4,
       5.6.5 and 5.6.6 below, (a) in the event that Landlord shall not have
       exercised the termination right as set forth in Section 5.6.2 or shall
       have failed to give any or timely notice under Section 5.6.2, then for a
       period of one hundred and twenty (120) days (i) after the receipt of
       Landlord's notice stating that Landlord does not elect the termination
       right or (ii) after the expiration of the six (6) business day period
       referred to in Section 5.6.4 in the event Landlord shall not give any or
       timely notice under Section 5.6.2 or (b) in the event Landlord has no
       termination right (in whole or in part) under Section 5.6.2, as the case
       may be, Tenant shall have the right to assign this Lease or sublet the
       whole or part of the Premises in accordance with Tenant's notice to
       Landlord given as provided in Section 5.6.4 provided that, in each
       instance, Tenant first obtains the express prior written consent of
       Landlord, which consent shall not be unreasonably withheld, conditioned
       or delayed. Landlord shall exercise its rights under this Section 5.6.3
       within the time period set forth in Section 5.6.4 hereof. Without
       limitation, Landlord shall not be deemed to be unreasonably withholding
       its consent to such a proposed assignment or subleasing if:

            (a)   the proposed assignee or subtenant is not of a character
                  consistent with the operation of a first class office building
                  (by way of example Landlord shall not be deemed to be
                  unreasonably withholding its consent to an assignment or
                  subleasing to any governmental agency), or

            (b)   the proposed assignee or subtenant does not possess adequate
                  financial capability and liquidity to perform the Tenant
                  obligations as and when due or required, or

                                      46
<PAGE>
                                                                    Exhibit 10.9
            (c)   the assignee or subtenant proposes to use the Premises (or
                  part thereof) for a purpose other than the purpose for which
                  the Premises may be used as stated in Section 1.1 hereof, or

            (d)   the character of the business to be conducted or the proposed
                  use of the Premises by the proposed subtenant or assignee
                  shall (i) increase Landlord's Operating Expenses beyond that
                  which Landlord now incurs for use by Tenant; (ii) increase the
                  burden on elevators or other Building systems or equipment
                  over the burden prior to such proposed subletting or
                  assignment; or (iii) violate any provisions or restrictions
                  contained herein relating to the use or occupancy of the
                  Premises. Landlord shall give Tenant reasonable information
                  supporting any of items (i), (ii) and/or (iii) hereof at such
                  time as Landlord gives its denial of Tenant's request for
                  approval.

            (e)   there shall be existing an Event of Default at the time such
                  consent is requested (defined in Section 7.1).


5.6.4  Tenant shall give Landlord notice of any proposed sublease or assignment,
       and said notice shall specify the provisions of the proposed assignment
       or subletting, including (a) the name and address of the proposed
       assignee or subtenant, (b) in the case of a proposed assignment or
       subletting pursuant to Section 5.6.2 or Section 5.6.3, such information
       as to the proposed assignee's or proposed subtenant's net worth and
       financial capability and standing as may reasonably be required for
       Landlord to make the determination referred to in Section 5.6.2 or
       Section 5.6.3 above (provided, however, that Landlord shall hold such
       information confidential having the right to release same to its
       officers, accountants, attorneys and mortgage lenders on a confidential
       basis), (c) all of the terms and provisions upon which the proposed
       assignment or subletting is to be made, (d) in the case of a proposed
       assignment or subletting pursuant to Section 5.6.2 or Section 5.6.3, all
       other information reasonably necessary to make the determination referred
       to in Section 5.6.2 or Section 5.6.3 above and (e) in the case of a
       proposed assignment or subletting pursuant to Section 5.6.1 above, such
       information as may be reasonably required by Landlord to determine that
       such proposed assignment or subletting complies with the requirements of
       said Section 5.6.1.

       In the case of both Section 5.6.2 and Section 5.6.3, Landlord shall
       exercise its rights thereunder within six (6) business days after receipt
       of Tenant's notice; provided, however, that not later than the sixth
       (6th) business day after receipt of such notice, Landlord shall have the
       right to give written notice to Tenant (i) specifying in reasonable


                                      47
<PAGE>
                                                                    Exhibit 10.9
       detail respects in which Tenant's notice and the materials submitted
       therewith are insufficient for Landlord to make the determinations under
       and in accordance with Sections 5.6.2 and 5.6.3 and (ii) requesting
       additional information from Tenant, in which case the six (6) business
       day period shall recommence to run from Landlord's receipt of such
       additional information.

       If Landlord shall consent to the proposed assignment or subletting, as
       the case may be, then, in such event, Tenant may thereafter sublease (the
       whole or part of the Premises) or assign, in either case pursuant to
       Tenant's notice, as given hereunder; provided, however, that if such
       assignment or sublease shall not be executed and delivered to Landlord
       within one hundred and twenty (120) days after the date of Landlord's
       consent, the consent shall be deemed null and void and the provisions of
       Sections 5.6.2 and/or 5.6.3, as the case may be, shall be applicable.

5.6.5  In addition, in the case of any assignment or subleasing as to which
       Landlord may consent (other than an assignment or subletting permitted
       under Section 5.6.1 hereof) such consent shall be upon the express and
       further condition, covenant and agreement, and Tenant hereby covenants
       and agrees that, in addition to the Annual Fixed Rent, Additional Rent
       and other charges to be paid pursuant to this Lease, fifty percent (50%)
       of the "Assignment/Sublease Profits" (hereinafter defined), if any, shall
       be paid to Landlord.

       The "Assignment/Sublease Profits" shall be the excess, if any, of (a) the
       "Assignment/Sublease Net Revenues" as hereinafter defined over (b) the
       Annual Fixed Rent and Additional Rent and other charges provided in this
       Lease(pro-rated in the case of a partial subletting). The
       "Assignment/Sublease Net Revenues" shall be the fixed rent, Additional
       Rent and all other charges and sums payable either initially or over the
       term of the sublease or assignment plus all other profits and increases
                                          ----
       to be derived by Tenant as a result of such subletting or assignment,
       less the reasonable costs of Tenant incurred in such subleasing or
       assignment (the definition of which shall include but not necessarily be
       limited to rent concessions, brokerage commissions and alteration
       allowances) amortized over the term of the sublease or assignment.

       All payments of the Assignment/Sublease Profits due Landlord shall be
       made within ten (10) days of receipt of same by Tenant.

5.6.6  (A)  It shall be a condition of the validity of any assignment or
       subletting of right under Section 5.6.1 above, or consented to under
       Section 5.6.3 above, that the assignee or sublessee agrees directly with
       Landlord, in form reasonably satisfactory to Landlord, to be bound by all
       the obligations of the Tenant hereunder, including, without limitation,
       the

                                      48
<PAGE>
 
                                                                    Exhibit 10.9
     obligation to pay the rent and other amounts provided for under this Lease
     (but in the case of a partial subletting, such subtenant shall agree on a
     pro rata basis to be so bound) including the provisions of Sections 5.6
     through 5.6.6 hereof, but such assignment or subletting shall not relieve
     the Tenant named herein of any of the obligations of the Tenant hereunder,
     Tenant shall remain fully and primarily liable therefor and the liability
     of Tenant and such assignee (or subtenant, as the case may be) shall be
     joint and several.  Further, and notwithstanding the foregoing, the
     provisions hereof shall not constitute a recognition of the assignment or
     the assignee thereunder or the sublease or the subtenant thereunder, as the
     case may be, and at Landlord's option, upon the termination of the Lease,
     the assignment or sublease shall be terminated unless otherwise expressly
     agreed to in writing by Landlord.

     (B)  As Additional Rent, Tenant shall reimburse Landlord promptly for
     reasonable out of pocket legal and other expenses incurred by Landlord in
     connection with any request by Tenant for consent to assignment or
     subletting but (i) in no event more than $2,500.00 per transaction if
     outside counsel is utilized by Landlord and (ii) in no event more than
     $1,500.00 per transaction if inside counsel is utilized by Landlord.

     (C)  If this Lease is assigned, or if the Premises or any part thereof are
     sublet or occupied by anyone other than Tenant, Landlord may upon prior
     written notice to Tenant, at any time and from time to time, collect rent
     and other charges from the assignee, sublessee or occupant and apply the
     net amount collected to the rent and other charges herein reserved, but no
     such assignment, subletting, occupancy or collection shall be deemed a
     waiver of this covenant, or a waiver of the provisions of Sections 5.6
     through 5.6.6 hereof, or the acceptance of the assignee, sublessee or
     occupant as a tenant or a release of Tenant from the further performance by
     Tenant of covenants on the part of Tenant herein contained, the Tenant
     herein named to remain primarily liable under this Lease.

     (D)  The consent by Landlord to an assignment or subletting under any of
     the provisions of Sections 5.6.1 or 5.6.3 shall in no way be construed to
     relieve Tenant from obtaining the express consent in writing to Landlord to
     any further assignment or subletting.

5.7  (A)  To defend with counsel first approved by Landlord (which approval
     shall not be unreasonably withheld or delayed, it being agreed that counsel
     selected by Tenant's liability insurance carrier shall be deemed approved),
     save harmless, and indemnify Landlord from any liability for injury, loss,
     accident or damage to any person or property, and from any claims, actions,
     proceedings and expenses and costs in connection therewith (including
     without limitation reasonable counsel fees) (i) arising from or claimed to
     have 

                                      -49-
<PAGE>
 
                                                                    Exhibit 10.9
     arisen from (a) the omission, fault, willful act, negligence or other
     misconduct of Tenant or Tenant's contractors, licensees, invitees, agents,
     servants, independent contractors or employees or (b) any use made or thing
     done or occurring on the Premises not due to the omission, fault, willful
     act, negligence or other misconduct of Landlord or Landlord's contractors,
     licensees, invitees, agents, servants or employees, or (ii) resulting from
     the failure of Tenant to perform and discharge its covenants and
     obligations under this Lease; to maintain  commercial general liability
     insurance or comprehensive general liability insurance written on an
     occurrence basis with a broad form comprehensive liability endorsement
     covering the Premises insuring Landlord and Landlord's managing agent (and
     such persons as are in privity of estate with Landlord and Landlord's
     managing agent as may be set out in a written notice to Tenant from time to
     time) as additional insureds as well as Tenant with limits which shall, at
     the commencement of the Term, be at least equal to those stated in Section
     1.1 and from time to time during the Term shall be for such higher limits,
     if any, as are customarily carried in Greater Boston with respect to
     similar properties or which may reasonably be required by Landlord, and
     workmen's compensation insurance with statutory limits covering all of
     Tenant's employees working in the Premises, and to deposit with Landlord on
     or before the Commencement Date and concurrent with all renewals thereof,
     certificates for such insurance bearing the endorsement that the policies
     will not be canceled until after thirty (30) days' written notice to
     Landlord.  All insurance required to be maintained by Tenant pursuant to
     this Lease shall be maintained with responsible companies qualified to do
     business, and in good standing, in the Commonwealth of Massachusetts and
     which have a rating of at least "A-" and are within a financial size
     category of not less than "Class VIII" in the most current Best's Key
     Rating Guide or such similar rating as may be reasonably selected by
     Landlord if such Guide is no longer published.

     (B)  Subject to the limitations of Section 8.4 hereof, to the extent not
     resulting from any act, omission, fault, negligence or misconduct of Tenant
     or its contractors, agents, licensees, invitees, servants or employees,
     Landlord agrees to indemnify, defend and save harmless Tenant from and
     against any claim arising from any accident or injury to any person
     occurring in the Premises, in the Building or on the Site after the date
     that possession of the Premises is first delivered to Tenant and until the
     expiration or earlier termination of the Lease Term, to the extent such
     accident or injury results from the negligence of Landlord or Landlord's
     employees, agents or contractors provided, however that in no event shall
     the aforesaid indemnity render Landlord responsible or liable for any loss
     or damage to fixtures or personal property of Tenant and Landlord shall in
     no event be liable for any indirect or consequential damages; and provided,
     further, that the provisions of this Section shall not be applicable (i) to
     the holder of any mortgage now or hereafter on the Site or the Building
     (whether or not such holder shall be a mortgagee in possession of or shall
     have exercised any rights under a conditional, collateral or other

                                      -50-
<PAGE>
 
                                                                    Exhibit 10.9
     assignment of leases and/or rents respecting, the Site and/or Building) or
     (ii) any person acquiring title as a result of, or subsequent to, a
     foreclosure of any such mortgage or a deed in lieu of foreclosure, except
     to the extent of liability insurance maintained by the foregoing.  The
     foregoing provisions of this Section 5.7(B) shall not be applicable to the
     matters set forth in Section 4.4 hereof.

5.8  That all of the furnishings, fixtures, equipment, effects and property of
     every kind, nature and description of Tenant and of all persons claiming
     by, through or under Tenant which, during the continuance of this Lease or
     any occupancy of the Premises by Tenant or anyone claiming under Tenant,
     may be on the Premises or elsewhere in the Building or on the Site, shall
     be at the sole risk and hazard of Tenant, and if the whole or any part
     thereof shall be destroyed or damaged by fire, water or otherwise, or by
     the leakage or bursting of water pipes, or other pipes, by theft or from
     any other cause, no part of said loss or damage is to be charged to or be
     borne by Landlord, except that Landlord shall in no event be indemnified or
     held harmless or exonerated from any liability to Tenant or to any other
     person, for any injury, loss, damage or liability to the extent such
     indemnity, hold harmless or exoneration is prohibited by law.  Further,
     Tenant, at Tenant's expense, shall maintain at all times during the Term of
     this Lease insurance against loss or damage covered by the so-called "all
     risk" type insurance coverage with respect to Tenant's fixtures, equipment,
     goods, wares and merchandise, tenant improvements made by or paid for by
     Tenant, and other property of Tenant (collectively "Tenant's Property").
     Such insurance shall be in an amount at least equal to the full replacement
     cost of Tenant's Property.

5.9  To permit Landlord and its agents to examine the Premises at reasonable
     times and, if Landlord shall so elect, to make any repairs or replacements
     Landlord may deem necessary (excluding the interior painting and cosmetic
     decoration permitted to be made by Tenant under and on the terms set forth
     in Section 3.3 hereof), to remove, at Tenant's expense, any alterations,
     addition, signs, curtains, blinds, shades, awnings, aerials, flagpoles, or
     the like not consented to in writing; and to show the Premises to
     prospective tenants during the nine (9) months preceding expiration of the
     Term and to prospective purchasers and mortgagees at all reasonable times.
     Except in the case of emergencies, such examination and entry shall be upon
     reasonable advance notice to Tenant and in accordance with Tenant's
     reasonable security requirements for entry into and examination of the
     Premises.

5.10 Not to place a load upon the Premises exceeding an average rate of 100
     pounds of live load per square foot of floor area (partitions shall be
     considered as part of the live load); and not to move any safe, vault or
     other heavy equipment in, about or out of the Premises except in such
     manner and at such time as Landlord shall in each instance authorize;

                                      -51-
<PAGE>
 
                                                                    Exhibit 10.9
     Tenant's business machines and mechanical equipment which cause vibration
     or noise that may be transmitted to the Building structure or to any other
     space in the Building shall be so installed, maintained and used by Tenant
     so as to eliminate such vibration or noise.

5.11 To pay promptly when due all taxes which may be imposed upon Tenant's
     Property in the Premises to whomever assessed.

5.12 To comply with all applicable Legal Requirements now or hereafter in force
     which shall impose a duty on Landlord or Tenant relating or resulting
     solely from Tenant's use or occupancy of the Premises; provided that Tenant
     shall not be required to make any alterations or additions to the
     structure, roof, exterior and load bearing walls, foundation, structural
     floor slabs and other structural elements of the Building unless and only
     to the extent the same are required by such Legal Requirements solely as a
     result of Tenant's use or occupancy of the Premises beyond normal office
     use of space of this kind.  Tenant shall promptly pay all fines, penalties
     and damages that may arise out of or be imposed because of its failure to
     comply with the provisions of this Section 5.12.

5.13 To pay as Additional Rent all reasonable costs, counsel and other fees
     incurred by Landlord in connection with the successful enforcement by
     Landlord of any obligations of Tenant under this Lease.


                                   ARTICLE VI
                                   ----------
                                        
                                 CASUALTY AND TAKING
                                 -------------------

6.1  In case during the Lease Term the Building or the Site are damaged by fire
     or other casualty and such fire or casualty damage cannot, in the ordinary
     course, reasonably be expected to be repaired within two hundred ten (210)
     days from the time that repair work would commence, Landlord may, at its
     election, terminate this Lease by notice given to Tenant within sixty (60)
     days after the date of such fire or other casualty, specifying the
     effective date of termination.  The effective date of termination specified
     by Landlord shall not be less than thirty (30) days nor more than forty-
     five (45) days after the date of notice of such termination.

     In case during the Lease Term, the Premises are damaged by fire or other
     casualty and such fire or casualty damage cannot, in the ordinary course,
     reasonably be expected to be repaired within two hundred ten (210) days
     (and/or as to special work or work which requires long lead time then if
     such work cannot reasonably be expected to be repaired within such
     additional time as is reasonable under the circumstances given the nature
     of 

                                      -52-
<PAGE>
 
                                                                    Exhibit 10.9
     the work) from the time that repair work would commence, Tenant may, at
     its election, terminate this Lease by notice given to Landlord within sixty
     (60) days after the date of such fire or other casualty, specifying the
     effective date of termination.  The effective date of termination specified
     by Tenant shall be not less than thirty (30) days nor more than forty-five
     (45) days after the date of notice of such termination.

     For purposes of Sections 6.1 and 6.2, the repair work shall be deemed to
     have commenced on the first to occur of (i) the date of the issuance of a
     building permit by the Town of Lexington for such repair work and (ii)
     forty-five (45) days following the date of the fire or other casualty.

     Unless terminated pursuant to the foregoing provisions, this Lease shall
     remain in full force and effect following any such damage subject, however,
     to the following provisions.

     If the Building or the Site or any part thereof are damaged by fire or
     other casualty and this Lease is not so terminated, or Landlord or Tenant
     have no right to terminate this Lease, and in any such case the holder of
     any mortgage which includes the Building as a part of the mortgaged
     premises or any ground lessor of any ground lease which includes the Site
     as part of the demised premises allows the net insurance proceeds to be
     applied to the restoration of the Building (and/or the Site), Landlord
     shall, promptly after such damage and the determination of the net amount
     of insurance proceeds available, use due diligence to restore the Premises
     and the Building in the event of damage thereto (excluding Tenant's
     Property) substantially the same condition the Premises were in immediately
     prior to such fire or causality (excluding Tenant's Property and any
     alterations, additions or improvements constructed by Tenant) and a just
     proportion of the Annual Fixed Rent, Tenant's share of Operating Costs and
     Tenant's share of real estate taxes shall be abated commencing on the date
     of such fire or casualty according to the nature and extent of the injury
     to the Premises, until the Premises shall have been restored by Landlord
     substantially into such condition except for punch list items and long lead
     items.  Notwithstanding anything herein contained to the contrary, Landlord
     shall not be obligated to expend for such repair and restoration any amount
     in excess of the net insurance proceeds.

     If such restoration is not completed within two hundred forty (240) days
     from the date that repair or restoration work actually commences,  such
     period to be subject, however, to extension where the delay in completion
     of such work is due to causes beyond Landlord's reasonable control (but in
     no event beyond two hundred seventy (270) days from the date repair or
     restoration work actually commences), Tenant shall have the right to
     terminate this Lease at any time after the expiration of such two hundred
     forty (240) 

                                      -53-
<PAGE>
 
                                                                    Exhibit 10.9
     day  period (as extended), which right shall continue until the
     restoration is substantially completed.  Such termination shall be
     effective as of the thirtieth (30th) day after the date of receipt by
     Landlord of Tenant's notice, with the same force and effect as if such date
     were the date originally established as the expiration date hereof unless,
     within thirty (30) days after Landlord's receipt of Tenant's notice, such
     restoration is substantially completed, in which case Tenant's notice of
     termination shall be of no force and effect and this Lease and the Lease
     Term shall continue in full force and effect.

6.2  Notwithstanding anything to the contrary contained in this Lease, if the
     Building or the Premises shall be substantially damaged by fire or casualty
     as the result of a risk not covered by the forms of casualty insurance at
     the time maintained by Landlord and such fire or casualty damage cannot, in
     the ordinary course, reasonably be expected to be repaired within ninety
     (90) days from the time that repair work would commence, Landlord may, at
     its election, terminate the Term of this Lease by notice to the Tenant
     given within thirty (30) days after such loss.  If Landlord shall give such
     notice, then this Lease shall terminate as of the date of such notice with
     the same force and effect as if such date were the date originally
     established as the expiration date hereof.

6.3  If the entire Building, or such portion of the Premises as to render the
     balance (if reconstructed to the maximum extent practicable in the
     circumstances) unsuitable for Tenant's purposes, shall be taken by
     condemnation or right of eminent domain, Landlord or Tenant shall have the
     right to terminate this Lease by notice to the other of its desire to do
     so, provided that such notice is given not later than thirty (30) days
     after Tenant has been deprived of possession.  If either party shall give
     such notice, then this Lease shall terminate as of the date of such notice
     with the same force and effect as if such date were the date originally
     established as the expiration date hereof.

     Further, if so much of the Building shall be so taken that continued
     operation of the Building would be uneconomic as a result of the taking,
     Landlord shall have the right to terminate this Lease by giving notice to
     Tenant of Landlord's desire to do so not later than thirty (30) days after
     Tenant has been deprived of possession of the Premises (or such portion
     thereof as may be taken).  If Landlord shall give such notice, then this
     Lease shall terminate as of the date of such notice with the same force and
     effect as if such date were the date originally established as the
     expiration date hereof.

     Should any part of the Premises be so taken or condemned during the Lease
     Term hereof, and should this Lease not be terminated in accordance with the
     foregoing provisions, and the holder of any mortgage which includes the
     Premises as part of the mortgaged premises or any ground lessor of any
     ground lease which includes the Site as part of the demised premises allows
     the net condemnation proceeds to be applied to the restoration of the
     Building, Landlord agrees, after the determination of the net amount of

                                      -54-
<PAGE>
 
                                                                    Exhibit 10.9
     condemnation proceeds available to Landlord, to use due diligence to put
     what may remain of the Premises into proper condition for use and
     occupation as nearly like the condition of the Premises prior to such
     taking as shall be practicable (excluding Tenant's Property).
     Notwithstanding the foregoing, Landlord shall not be obligated to expend
     for such repair and restoration any amount in excess of the net
     condemnation proceeds.

     If the Premises shall be affected by any exercise of the power of eminent
     domain, then the Annual Fixed Rent, Tenant's share of operating costs and
     Tenant's share of real estate taxes shall be justly and equitably abated
     and reduced according to the nature and extent of the loss of use thereof
     suffered by Tenant; and in case of a taking which permanently reduces the
     Rentable Floor Area of the Premises, a just proportion of the Annual Fixed
     Rent, Tenant's share of operating costs and Tenant's share of real estate
     taxes shall be abated for the remainder of the Lease Term.

6.4  Landlord shall have and hereby reserves to itself any and all rights to
     receive awards made for damages to the Premises, the Building, the Complex
     and the Site and the leasehold hereby created, or any one or more of them,
     accruing by reason of exercise of eminent domain or by reason of anything
     lawfully done in pursuance of public or other authority.  Tenant hereby
     grants, releases and assigns to Landlord all Tenant's rights to such
     awards, and covenants to execute and deliver such further assignments and
     assurances thereof as Landlord may from time to time request.

     Nothing contained herein shall be construed to prevent Tenant from
     prosecuting in any condemnation proceeding a claim for the value of any of
     Tenant's usual trade fixtures installed in the Premises by Tenant at
     Tenant's expense and for relocation and moving expenses, provided that such
     action and any resulting award shall not affect or diminish the amount of
     compensation otherwise recoverable by Landlord from the taking authority.



                                  ARTICLE VII
                                  -----------
 
                                    DEFAULT
                                    -------

7.1  (a)  If at any time subsequent to the date of this Lease any one or more of
     the following events (herein sometimes called an "Event of Default") shall
     occur:

          (i)  Tenant shall fail to pay the fixed rent, Additional Rent or other
               charges for which provision is made herein on or before the date
               on which the same become due and payable, and the same continues
               for five (5) days after 

                                      -55-
<PAGE>
 
                                                                    Exhibit 10.9
               written notice from Landlord thereof, or

          (ii) Landlord having rightfully given the notice specified in
               subdivision (a) above twice in any calendar year, Tenant shall
               thereafter in the same calendar year fail to pay the fixed rent,
               Additional Rent or other charges on or before the date on which
               the same become due and payable, or,

         (iii) Tenant shall neglect or fail to perform or observe any other
               covenant herein contained on Tenant's part to be performed or
               observed and Tenant shall fail to remedy the same within thirty
               (30) days after written notice to Tenant specifying such neglect
               or failure, or if such failure is of such a nature that Tenant
               cannot reasonably remedy the same within such thirty (30) day
               period, Tenant shall fail to commence promptly to remedy the same
               and to prosecute such remedy to completion with diligence and
               continuity; or

          (iv) Tenant's leasehold interest in the Premises shall be taken on
               execution or by other process of law directed against Tenant; or

          (v)  Tenant shall make an assignment for the benefit of creditors or
               shall file a voluntary petition in bankruptcy or shall be
               adjudicated bankrupt or insolvent, or shall file any petition or
               answer seeking any reorganization, arrangement, composition,
               readjustment, liquidation, dissolution or similar relief for
               itself under any present or future Federal, State or other
               statute, law or regulation for the relief of debtors, or shall
               seek or consent to or acquiesce in the appointment of any
               trustee, receiver or liquidator of Tenant or of all or any
               substantial part of its properties, or shall admit in writing its
               inability to pay its debts generally as they become due; or

          (vi) A petition shall be filed against Tenant in bankruptcy or under
               any other law seeking any reorganization, arrangement,
               composition, readjustment, liquidation, dissolution, or similar
               relief under any present or future Federal, State or other
               statute, law or regulation and shall remain undismissed or
               unstayed for an aggregate of ninety (90) days (whether or not
               consecutive), or if any debtor in possession (whether or not
               Tenant) trustee, receiver or liquidator of Tenant or of all or
               any substantial part of its properties or of the Premises shall
               be appointed without the consent or acquiescence of Tenant and
               such appointment shall remain unvacated or unstayed for an
               aggregate of ninety (90) days (whether or not consecutive)--

                                      -56-
<PAGE>
 
                                                                    Exhibit 10.9
     then, and in any of said cases (notwithstanding any license of a former
     breach of covenant or waiver of the benefit hereof or consent in a former
     instance), Landlord lawfully may, immediately or at any time thereafter,
     and without demand or further notice terminate this Lease by notice to
     Tenant, specifying a date not less than ten (10) days after the giving of
     such notice on which this Lease shall terminate, and this Lease shall come
     to an end on the date specified therein as fully and completely as if such
     date were the date herein originally fixed for the expiration of the Lease
     Term (Tenant hereby waiving any rights of redemption), and Tenant will then
     quit and surrender the Premises to Landlord, but Tenant shall remain liable
     as hereinafter provided.

     (b)  If this Lease shall have been terminated as provided in this Article,
     then Landlord may, in accordance with applicable laws, re-enter the
     Premises, either by force, summary proceedings, ejectment or otherwise, and
     remove and dispossess Tenant and all other persons and any and all property
     from the same, as if this Lease had not been made.

     (c)  In the event that this Lease is terminated under any of the provisions
     contained in Section 7.1 (a) or shall be otherwise terminated by breach of
     any obligation of Tenant, Tenant covenants and agrees forthwith to pay and
     be liable for, on the days originally fixed herein for the payment thereof,
     amounts equal to the several installments of rent and other charges
     reserved as they would, under the terms of this Lease, become due if this
     Lease had not been terminated or if Landlord had not entered or re-entered,
     as aforesaid, and whether the Premises be relet or remain vacant, in whole
     or in part, or relet for a period less than the remainder of the Term, and
     for the whole thereof, but in the event the Premises be relet by Landlord,
     Tenant shall be entitled to a credit in the net amount of rent and other
     charges received by Landlord in reletting, after deduction of all expenses
     incurred in reletting the Premises (including, without limitation,
     remodeling costs, brokerage fees and the like), and in collecting the rent
     in connection therewith, in the following manner:

     Amounts received by Landlord after reletting shall first be applied against
     such Landlord's expenses, until the same are recovered, and until such
     recovery, Tenant shall pay, as of each day when a payment would fall due
     under this Lease, the amount which Tenant is obligated to pay under the
     terms of this Lease (Tenant's liability prior to any such reletting and
     such recovery not in any way to be diminished as a result of the fact that
     such reletting might be for a rent higher than the rent provided for in
     this Lease); when and if such expenses have been completely recovered, the
     amounts received from reletting by Landlord as have not previously been
     applied shall be credited against Tenant's obligations as of each day when
     a payment would fall due under this Lease, and only the net amount thereof
     shall be payable by Tenant.  Further, amounts received by 

                                      -57-
<PAGE>
 
                                                                    Exhibit 10.9
     Landlord from such reletting for any period shall be credited only against
     obligations of Tenant allocable to such period, and shall not be credited
     against obligations of Tenant hereunder accruing subsequent or prior to
     such period; nor shall any credit of any kind be due for any period after
     the date when the term of this Lease is scheduled to expire according to
     its terms.

     (d)(i) At any time after such termination and whether or not Landlord shall
     have collected any damages as aforesaid, Tenant shall pay to Landlord as
     liquidated final damages and in lieu of all other damages beyond the date
     of notice from Landlord to Tenant, at Landlord's election, such a sum as at
     the time of the giving of such notice represents the amount of the excess,
     if any, of the total rent and other benefits which would have accrued to
     Landlord under this Lease from the date of such notice for what would be
     the then unexpired Lease Term if the Lease terms had been fully complied
     with by Tenant over and above the then cash rental value (in advance) of
     the Premises for the balance of the Lease Term.

     (d)(ii) For the purposes of this Article, if Landlord elects to require
     Tenant to pay damages in accordance with the immediately preceding
     paragraph, the total rent shall be computed by assuming that Tenant's share
     of excess taxes, Tenant's share of excess operating costs and Tenant's
     share of excess electrical costs would be, for the balance of the unexpired
     Term from the date of such notice, the amount thereof (if any) for the
     immediately preceding annual period payable by Tenant to Landlord.

     (e) In case of any Event of Default, re-entry, dispossession by summary
     proceedings or otherwise, Landlord may (i) re-let the Premises or any part
     or parts thereof, either in the name of Landlord or otherwise, for a term
     or terms which may at Landlord's option be equal to or less than or exceed
     the period which would otherwise have constituted the balance of the Term
     of this Lease and may grant concessions or free rent to the extent that
     Landlord considers advisable or necessary to re-let the same and (ii) may
     make such alterations, repairs and decorations in the Premises as Landlord
     in its sole judgment considers advisable or necessary for the purpose of
     reletting the Premises; and the making of such alterations, repairs and
     decorations shall not operate or be construed to release Tenant from
     liability hereunder as aforesaid.  Landlord shall use reasonable efforts to
     re-let the Premises after Tenant vacates the Premises (which shall be
     deemed satisfied by Landlord offering the Premises for lease either
     directly or through a commercial real estate leasing broker or brokerage
     firm) but the failure to re-let shall not give rise to any claim, action or
     counterclaim by Tenant nor release, limit, reduce or otherwise modify
     Tenant's liability.  Also, Landlord shall in no event be liable in any way
     whatsoever for failure to re-let the Premises, or, in the event that the
     Premises are re-let, for failure to collect the rent under re-letting.
     Tenant hereby expressly waives any and all rights of 

                                      -58-
<PAGE>
 
                                                                    Exhibit 10.9
     redemption granted by or under any present or future laws in the event of
     Tenant being evicted or dispossessed, or in the event of Landlord obtaining
     possession of the Premises, by reason of the violation by Tenant of any of
     the covenants and conditions of this Lease.

     (f) The specified remedies to which Landlord may resort hereunder are not
     intended to be exclusive of any remedies or means of redress to which
     Landlord may at any time be entitled lawfully, and Landlord may invoke any
     remedy (including the remedy of specific performance) allowed at law or in
     equity as if specific remedies were not herein provided for.  Further,
     nothing contained in this Lease shall limit or prejudice the right of
     Landlord to prove and obtain in proceedings for bankruptcy or insolvency by
     reason of the termination of this Lease, an amount equal to the maximum
     allowed by any statute or rule of law in effect at the time when, and
     governing the proceedings in which, the damages are to be proved, whether
     or not the amount be greater, equal to, or less than the amount of the loss
     or damages referred to above.

7.2  Landlord shall in no event be in default in the performance of any of
     Landlord's obligations hereunder (i) unless and until Landlord shall have
     failed to perform such obligations within thirty (30)  days, after written
     notice by Tenant to Landlord properly specifying wherein Landlord has
     failed to perform any such obligation or (ii) if such obligation cannot
     reasonably be performed within said thirty (30) day period, unless Landlord
     (a) fails to commence to perform such obligations within said thirty (30)
     day period and (b) fails to diligently and continuously pursue same to
     completion.


                                 ARTICLE VIII
                                 ------------

8.1  Tenant covenants and agrees that Tenant will not do or permit anything to
     be done in or upon the Premises, or bring in anything or keep anything
     therein, which shall invalidate or increase the rate of insurance on the
     Premises or on the Building above the standard rate applicable to premises
     being occupied for the use to which Tenant has agreed to devote the
     Premises; and Tenant further agrees that, in the event that Tenant shall do
     any of the foregoing, Tenant will promptly pay to Landlord, on demand, any
     such increase resulting therefrom, which shall be due and payable as
     Additional Rent thereunder, provided Landlord has previously notified
     Tenant in writing that Tenant's use or activities would or will result in
     an increase in Landlord's insurance or would or will result in an
     invalidation of Landlord's insurance covering the Property.  Landlord
     hereby acknowledges that the "Permitted Use" (as defined in Section 1.1
     hereof) does not invalidate, or increase the rate of, Landlord's insurance
     but Landlord makes no such statement as to Tenant's specific activities.

8.2  Failure on the part of Landlord or Tenant to complain of any action or non-
     action on the 

                                      -59-
<PAGE>
                                                                                
                                                                    Exhibit 10.9
     
     
     part of the other, no matter how long the same may continue, shall never be
     a waiver by Tenant or Landlord, respectively, of any of its rights
     hereunder. Further, no waiver at any time of any of the provisions hereof
     by Landlord or Tenant shall be construed as a waiver of any of the other
     provisions hereof, and a waiver at any time of any of the provisions hereof
     shall not be construed as a waiver at any subsequent time of the same
     provisions. The consent or approval of Landlord or Tenant to or of any
     action by the other requiring such consent or approval shall not be
     construed to waive or render unnecessary Landlord's or Tenant's consent or
     approval to or of subsequent similar act by the other.

     No payment by Tenant, or acceptance by Landlord, of a lesser amount than
     shall be due from Tenant to Landlord shall be treated otherwise than as a
     payment on account.  The acceptance by Landlord of a check for a lesser
     amount with an endorsement or statement thereon, or upon any letter
     accompanying such check, that such lesser amount is payment in full, shall
     be given no effect, and Landlord may accept such check without prejudice to
     any other rights or remedies which Landlord may have against Tenant.

8.3  The specific remedies to which Landlord may resort under the terms of this
     Lease are cumulative and are not intended to be exclusive of any other
     remedies or means of redress to which such party may be lawfully entitled
     at law or in equity in case of any breach or threatened breach by Tenant of
     any provisions of this Lease.

8.4  Tenant, subject to the terms and provisions of this Lease on payment of the
     rent and observing, keeping and performing all of the terms and provisions
     of this Lease on Tenant's part to be observed, kept and performed, shall
     lawfully, peaceably and quietly have, hold, occupy and enjoy the Premises
     during the Term, without hindrance or ejection by any persons lawfully
     claiming under Landlord to have title to the Premises superior to Tenant;
     the foregoing covenant of quiet enjoyment is in lieu of any other covenant,
     express or implied; and it is understood and agreed that this covenant and
     any and all other covenants of Landlord contained in this Lease shall be
     binding upon Landlord and Landlord's successors only with respect to
     breaches occurring during Landlord's or Landlord's successors' respective
     ownership of Landlord's interest hereunder, as the case may be.

     Further, Tenant specifically agrees to look solely to Landlord's then
     equity interest in the Building at the time owned, or in which Landlord
     holds an interest as ground lessee, for recovery of any judgment from
     Landlord; it being specifically agreed that neither Landlord (original or
     successor), nor any partner in or of Landlord, nor any beneficiary of any
     Trust of which any person holding Landlord's interest is Trustee, shall
     ever be personally liable for any such judgment, or for the payment of any
     monetary obligation to Tenant.  The provision contained in the foregoing
     sentence is not intended to, and shall 

                                      -60-
<PAGE>

                                                                    Exhibit 10.9
 
     not, limit any right that Tenant might otherwise have to obtain injunctive
     relief against Landlord or Landlord's successors in interest, or any action
     not involving the personal liability of Landlord (original or successor),
     any partner in or of Landlord, any successor Trustee to the persons named
     herein as Landlord, or any beneficiary of any Trust of which any person
     holding Landlord's interest is Trustee, to respond in monetary damages from
     Landlord's assets other than Landlord's equity interest aforesaid in the
     Building. In no event shall Landlord ever be liable to Tenant for any
     indirect or consequential damages suffered by Tenant from whatever cause.

8.5  After receiving written notice from any person, firm or other entity that
     it holds a mortgage which includes the Premises as part of the mortgaged
     premises, or that it is the ground lessor under a lease with Landlord, as
     ground lessee, which includes the Premises as a part of the demised
     premises, no notice from Tenant to Landlord shall be effective unless and
     until a copy of the same is given to such holder or ground lessor, and the
     curing of any of Landlord's defaults by such holder or ground lessor within
     the time period set forth in the Subordination, Non-Disturbance and
     Attornment Agreement between Tenant and such mortgagee or ground lessor
     shall be treated as performance by Landlord.  For the purposes of this
     Section 8.5 or Section 8.15, the term "mortgage" includes a mortgage on a
     leasehold interest of Landlord (but not one on Tenant's leasehold
     interest).

8.6  With reference to any assignment by Landlord or Landlord's interest in this
     Lease, or the rents payable hereunder, conditional in nature or otherwise,
     which assignment is made to the holder of a mortgage or ground lease on
     property which includes the Premises, Tenant agrees:

          (a)  That the execution thereof by Landlord, and the acceptance
               thereof by the holder of such mortgage or the ground lessor,
               shall never be treated as an assumption by such holder or ground
               lessor of any of the obligations of Landlord hereunder, unless
               such holder, or ground lessor, shall, by notice sent to Tenant,
               specifically otherwise elect; and

          (b)  That, except as aforesaid, such holder or ground lessor shall be
               treated as having assumed Landlord's obligations hereunder only
               upon foreclosure of such holder's mortgage and the taking of
               possession of the Premises, or, in the case of a ground lessor,
               the assumption of Landlord's position hereunder by such ground
               lessor.

               In no event shall the acquisition of title to the Building and
               the land on which the same is located by a purchaser which,
               simultaneously therewith, leases the entire Building or such land
               back to the seller thereof be treated 

                                      -61-
<PAGE>
 
                                                                    Exhibit 10.9
               as an assumption by such purchaser-lessor, by operation of law or
               otherwise, of Landlord's obligations hereunder, but Tenant shall
               look solely to such seller-lessee, and its successors from time
               to time in title, for performance of Landlord's obligations
               hereunder subject to the provisions of Section 8.4 hereof. In any
               such event, this Lease shall be subject and subordinate to the
               lease to such purchaser provided that such purchaser agrees to
               recognize the lease (including but not limited to the right of
               Tenant to use and occupy the Premises) upon the payment of rent
               and other charges payable by Tenant under this Lease and the
               performance by Tenant of Tenant's obligations under this Lease
               and provided that Tenant agrees to attorn to such purchaser. For
               all purposes, such seller-lessee, and its successors in title,
               shall be the landlord hereunder unless and until Landlord's
               position shall have been assumed by such purchaser-lessor.

8.7  No act or thing done by Landlord during the Lease Term shall be deemed an
     acceptance of a surrender of the Premises, and no agreement to accept such
     surrender shall be valid, unless in writing signed by Landlord.  No
     employee of Landlord or of Landlord's agents shall have any power to accept
     the keys of the Premises prior to the termination of this Lease.  The
     delivery of keys to any employee of Landlord or of Landlord's agents shall
     not operate as a termination of the Lease or a surrender of the Premises.

8.8  (A)  Tenant warrants and represents that Tenant has not dealt with any
     broker, finder or other agent in connection with the consummation of this
     Lease other than the Recognized Brokers, if any, designated in Section 1.1
     hereof; and in the event any claim is made against the Landlord relative to
     dealings by Tenant with brokers, finders or other agents other than the
     Recognized Brokers, if any, designated in Section 1.1 hereof, Tenant shall
     defend the claim against Landlord with counsel of Tenant's selection first
     approved by Landlord (which approval will not be unreasonably withheld) and
     save harmless and indemnify Landlord on account of loss, cost or damage
     which may arise by reason of such claim.

     (B)  Landlord warrants and represents that Landlord has not dealt with any
     broker, finder or other agent in connection with the consummation of this
     Lease other than the Recognized Brokers,  if any, designated in Section 1.1
     hereof; and in the event any claim is made against the Tenant relative to
     dealings by Landlord with brokers, finders or other agents other than the
     Recognized Brokers, if any, designated in Section 1.1 hereof, Landlord
     shall defend the claim against Tenant with counsel of Landlord's selection
     and approved by tenant (which approval shall not be unreasonably withheld)
     and save harmless and indemnify Tenant on account of loss, cost or damage
     which may arise by reason of such claim.  Landlord agrees that it shall be
     solely responsible for the payment 

                                      -62-
<PAGE>
                                                                    
                                                                    Exhibit 10.9
     

     of brokerage commissions to the Recognized Brokers, if any, designated in
     Section 1.1 hereof.

8.9  If any term or provision of this Lease, or the application thereof to any
     person or circumstance shall, to any extent, be invalid or unenforceable,
     the remainder of this Lease, or the application of such term or provision
     to persons or circumstances other than those as to which it is held invalid
     or unenforceable, shall not be affected thereby, and each term and
     provision of this Lease shall be valid and be enforced to the fullest
     extent permitted by law.

8.10 The obligations of this Lease shall run with the land, and except as herein
     otherwise provided, the terms hereof shall be binding upon and shall inure
     to the benefit of the successors and assigns, respectively, of Landlord and
     Tenant and, if Tenant shall be an individual, upon and to his heirs,
     executors, administrators, successors and assigns.  Each term and each
     provision of this Lease to be performed by Tenant shall be construed to be
     both a covenant and a condition.  The reference contained to successors and
     assigns of Tenant is not intended to constitute a consent to subletting or
     assignment by Tenant.

8.11 Tenant agrees not to record the within Lease, but each party hereto agrees
     that simultaneously with the execution of this Lease, they will execute a
     so-called Notice of Lease in form recordable and complying with applicable
     law and reasonably satisfactory to both Landlord's and Tenant's attorneys.
     In no event shall such document set forth rent or other charges payable by
     Tenant under this Lease; and any such document shall expressly state that
     it is executed pursuant to the provisions contained in this Lease, and is
     not intended to vary the terms and conditions of this Lease.

8.12 Whenever, by the terms of this Lease, notice shall or may be given either
     to Landlord or to Tenant, such notice shall be in writing and shall be sent
     by registered or certified mail or delivered by a recognized same-day
     courier or delivered by a recognized overnight courier in any such case
     delivery charges or postage charges prepaid:

          If intended for Landlord, addressed to Landlord at the address set
          forth on the first page of this Lease (or to such other address or
          addresses as may from time to time hereafter be designated by Landlord
          by like notice) with a copy to Landlord, Attention:  General Counsel.

          If intended for Tenant, addressed to Tenant at the address set forth
          on the second page of this Lease Attention: Chief Financial Officer
          except that from and after the Commencement Date the address of Tenant
          shall be the Premises (or to such other address or addresses as may
          from time to time hereafter be designated by Tenant by like notice)
          with a copy to Testa, Hurwitz & Thibeault, LLP, 125 High 

                                      -63-
<PAGE>
                                                                    Exhibit 10.9
          

          Street Tower, Boston, Massachusetts 02110, Attention: Real Estate
          Department.

     Except as otherwise provided herein, all such notices shall be effective
     when received; provided, that (i) if receipt is refused, notice shall be
     effective upon the first occasion that such receipt is refused or (ii) if
     the notice is unable to be delivered due to a change of address of which no
     notice was given, notice shall be effective upon the date such delivery was
     attempted.

     Where provision is made for the attention of an individual or department,
     the notice shall be effective only if the wrapper in which such notice is
     sent is addressed to the attention of such individual or department.

     Time is of the essence with respect to any and all notices and periods for
     giving notice or taking any action thereto under this Lease.

8.13 Employees or agents of Landlord have no authority to make or agree to make
     a lease or any other agreement or undertaking in connection herewith.  The
     submission of this document for examination and negotiation does not
     constitute an offer to lease, or a reservation of, or option for, the
     Premises, and this document shall become effective and binding only upon
     the execution and delivery hereof by both Landlord and Tenant.  All
     negotiations, considerations, representations and understandings between
     Landlord and Tenant are incorporated herein and may be modified or altered
     only by written agreement between Landlord and Tenant, and no act or
     omission of any employee or agent of Landlord shall alter, change or modify
     any of the provisions hereof.

8.14 The titles of the Articles throughout this Lease are for convenience and
     reference only, and the words contained therein shall in no way be held to
     explain, modify, amplify or aid in the interpretation, construction or
     meaning of the provisions of this Lease.

8.15 This Lease shall be subject and subordinate to any mortgage now or
     hereafter on the Site and/or the Building, or both, and to each advance
     made or hereafter to be made under any mortgage, and to all renewals,
     modifications, consolidations, replacements and extensions thereof and all
     substitutions therefor provided and on the condition that the holder of
     such mortgage agrees to recognize the rights of Tenant under this Lease
     (including the right to use and occupy the Premises) upon the payment of
     rent and other charges payable by Tenant under this Lease and the
     performance by Tenant of Tenant's obligations hereunder in which event
     Tenant shall agree to attorn to such holder and its successors as landlord,
     all of which agreements shall be set forth in a subordination, non-
     disturbance and attornment agreement which shall be reasonably satisfactory
     to Tenant, any such mortgagee and Landlord.  In confirmation of such
     subordination and recognition, Tenant 

                                      -64-
<PAGE>
                                                                    Exhibit 10.9
     shall execute and deliver promptly such instruments of subordination and
     recognition in accordance with the preceding provisions of this Section
     8.15. In the event that any mortgagee or its respective successor in title
     shall succeed to the interest of Landlord, then, this Lease shall
     nevertheless continue in full force and effect and Tenant shall and does
     hereby agree to attorn to such mortgagee or successor and to recognize such
     mortgagee or successor as its landlord. If any holder of a mortgage which
     includes the Premises, executed and recorded prior to the date of this
     Lease, shall so elect, this Lease and the rights of Tenant hereunder, shall
     be superior in right to the rights of such holder, with the same force and
     effect as if this Lease had been executed, delivered and recorded, or a
     statutory Notice hereof recorded, prior to the execution, delivery and
     recording of any such mortgage. The election of any such holder shall
     become effective upon either notice from such holder to Tenant in the same
     fashion as notices from Landlord to Tenant are to be given hereunder and,
     if required or desired by such holder, by the recording in the appropriate
     registry or recorder's office of an instrument in which such holder
     subordinates its rights under such mortgage to this Lease. With respect to
     the existing mortgagee, not later than twenty-one (21) days following the
     execution of this Lease by both parties Landlord shall obtain a
     subordination, non-disturbance and attornment agreement from said mortgagee
     in the form of Exhibit H and which shall be executed by Landlord (if
     required), Tenant and such mortgagee.

8.16 Recognizing that Landlord may find it necessary to establish to third
     parties, such as accountants, banks, potential or existing mortgagees,
     potential purchasers or the like, the then current status of performance
     hereunder, Tenant, on the request of Landlord made from time to time, will
     promptly furnish to Landlord, or any existing or potential holder of any
     mortgage encumbering the Premises, the Building, and/or the Site or any
     potential purchaser of the Premises, the Building, and/or the Site (each an
     "Interested Party"), a statement of the status of any matter pertaining to
     this Lease, including, without limitation, acknowledgments that (or the
     extent to which) each party is in compliance with its obligations under the
     terms of this Lease.  In addition, Tenant shall deliver to Landlord, or any
     Interested Party designated by Landlord, financial statements of Tenant and
     any guarantor of Tenant's obligations under this Lease, as reasonably
     requested by Landlord, including, but not limited to financial statements
     for the past three (3) years.  Any such status statement or financial
     statement delivered by Tenant pursuant to this Section 8.16 may be relied
     upon by any Interested Party.

8.17 (A)  If Tenant shall at any time default in the performance of any
     obligation under this Lease beyond applicable notice and cure period
     (except in the case of emergencies), Landlord shall have the right, but
     shall not be obligated, to enter upon the Premises and to perform such
     obligation notwithstanding the fact that no specific provision for such
     substituted performance by Landlord is made in this Lease with respect to
     such default.  

                                      -65-
<PAGE>
                                                                    Exhibit 10.9
     In performing such obligation, Landlord may make any payment of money or
     perform any other act. All sums so paid by Landlord (together with interest
     at the rate of one and one-half percentage points over the then prevailing
     prime rate in Boston as set by The First National Bank of Boston) and all
     reasonable costs and expenses in connection with the performance of any
     such act by Landlord, shall be deemed to be Additional Rent under this
     Lease and shall be payable to Landlord immediately on demand. Landlord may
     exercise the foregoing rights without waiving any other of its rights or
     releasing Tenant from any of its obligations under this Lease.

     (B) In the event (a) Landlord fails to make such repairs as are required of
     Landlord under this Lease or to perform any other obligations of Landlord
     hereunder within thirty (30) days after written notice from Tenant to
     Landlord and to the holder of any mortgage on the Property of which Tenant
     has been given written notice by Landlord specifying the nature of such
     repairs or other obligations or (b) if such repairs or other obligations
     are of the type which cannot be made or performed within such thirty (30)
     days, then if Landlord or the holder of any such mortgage (at the option of
     such mortgagee) fails to (i) commence making such repairs within thirty
     (30) days after such written notice from Tenant and (ii) thereafter
     prosecute such repairs or other obligations to completion with due
     diligence given the nature of such repairs or other obligations or (c) if
     such repairs or other obligations if not performed would constitute an
     emergency and would result in material damage to person or property, Tenant
     may specify a shorter time period than thirty (30) days (but not less than
     ten (10) days) to Landlord and such mortgagee and if Landlord or such
     mortgagee (at the option of such mortgagee) fails to (i) commence making
     such repairs within such shorter time period and (ii) thereafter prosecute
     such repairs or other obligations to completion with due diligence given
     such emergency nature thereof, then thereafter at any time prior to
     Landlord's commencing such repairs or other obligations, Tenant may, but
     need not, make such repairs or perform such other obligations and may make
     a demand on Landlord for payment of the reasonable out of pocket cost
     thereof and Landlord shall pay the reasonable out of pocket cost thereof;
     provided, however, if within thirty (30) days after receipt of such demand,
     Landlord shall not have paid same, then Tenant shall have the right to
     bring suit in a court of competent jurisdiction in the Commonwealth of
     Massachusetts seeking payment of the sum so claimed in Tenant's demand.  If
     Tenant  shall be successful in any such court action then Landlord shall
     pay to Tenant Tenant's reasonable out of pocket legal fees actually
     incurred in connection with such litigation.  However, in no event shall
     Tenant have the right to offset against, withhold or deduct from Annual
     Fixed Rent, or any Additional Rent or other charges payable under this
     Lease nor shall Landlord's failure to pay Tenant's demand be a default of
     Landlord or give Tenant the right to terminate this Lease, Tenant's right
     being to bring suit as aforesaid.

                                      -66-
<PAGE>

                                                                    Exhibit 10.9
8.18 Any holding over by Tenant after the expiration of the term of this Lease
     shall be treated as a tenancy at sufferance at one hundred and fifty
     percent (150%) of the rents and other charges herein (prorated on a daily
     basis) and shall otherwise be on the terms and conditions set forth in this
     Lease, as far as applicable; provided, however, that neither the foregoing
     nor any other term or provision of this Lease shall be deemed to permit
     Tenant to retain possession of the Premises or hold over in the Premises
     after the expiration or earlier termination of the Lease Term.

8.19 Any insurance carried by either party with respect to the Premises or
     property therein or occurrences thereon shall, if it can be so written
     without additional premium or with an additional premium which the other
     party agrees to pay, include a clause or endorsement denying to the insurer
     rights of subrogation against the other party to the extent rights have
     been waived by the insured prior to occurrence of injury or loss.  Each
     party, notwithstanding any provisions of this Lease to the contrary, hereby
     waives any rights of recovery against the other for injury or loss due to
     hazards covered by such insurance to the extent of the indemnification
     received thereunder.

8.20 Tenant agrees that the security deposit specified in Section 1.1 hereof
     (the "Security Deposit") will be paid within ten (10) days after Tenant's
     execution and delivery of this Lease (time being of the essence).  Subject
     to the following provisions of this Section, throughout the Term of this
     Lease (including any extension thereof) Landlord shall hold the same as
     security for the performance by Tenant of all obligations on the part of
     Tenant to be kept and performed under this Lease.  The Security Deposit
     shall be in the form of an irrevocable, unconditional, negotiable letter of
     credit (the "Letter of Credit") issued by and drawn on a bank, and in a
     form reasonably acceptable to Landlord, which Letter of Credit shall permit
     one or more draws thereunder to be made accompanied only by certification
     by Landlord that pursuant to the terms of this Lease, Landlord is entitled
     to apply such Letter of Credit and the proceeds thereof to a default of
     Tenant or is otherwise entitled to receive the proceeds thereof under the
     terms and provisions of this Lease.  Any such Letter of Credit shall be for
     a term of two (2) years (or for one (1) year if the issuer thereof
     regularly and customarily only issues letters of credit for a maximum term
     of one (1) year) and shall in either case be renewed by Tenant each year
     thereafter and each renewal shall be delivered to and received by Landlord
     not later than thirty (30) days before the expiration of the then current
     Letter of Credit (herein called a "Renewal Presentation Date").  In the
     event of a failure to so deliver such renewal Letter of Credit on or before
     the applicable Renewal Presentation Date, Landlord shall be entitled to
     present the then existing Letter of Credit for payment and to receive the
     proceeds thereof, which proceeds shall be held as Tenant's security
     deposit, subject to the terms of this Section 8.20.  In no event shall the
     Letter of Credit expire sooner than thirty (30) days after the expiration
     of the Lease Term (as extended).  Notwithstanding anything to the 

                                      -67-
<PAGE>
                                                                    Exhibit 10.9
     contrary contained herein, Landlord shall have the right from time to time
     without prejudice to any other right or remedy Landlord may have on account
     thereof, to draw on all or any portion of such deposit held as a Letter of
     Credit and to apply the proceeds of such Letter of Credit or any cash held
     as such deposit, or any part thereof, to Landlord's damages arising from
     any default on the part of Tenant which default has continued beyond
     applicable notice and cure periods. If Landlord so applies all or any
     portion of the Security Deposit, Tenant shall within seven (7) days after
     notice from Landlord deliver cash or a Letter of Credit to Landlord in an
     amount sufficient to restore the Security Deposit to the full amount stated
     in Section 1.1.

     Tenant not then being in default and having performed all of its
     obligations under this Lease, including, without limitation, the payment of
     all Annual Fixed Rent, Landlord shall return the Security Deposit, or so
     much thereof as shall not have theretofore been applied or returned in
     accordance with the terms of this Section 8.20, to Tenant on the expiration
     or earlier termination of the Term of this Lease and the surrender of
     possession of the Premises by Tenant to Landlord in the condition required
     by this Lease at such time.  Provided that on the third (3rd) anniversary
     of the Commencement Date (i) no Event of Default then exists and (ii) no
     event then exists which with the passage of time or the giving of notice or
     both would constitute an Event of Default and (iii) Landlord has not
     previously applied any portion of the Security Deposit in accordance with
     the terms of this Section or if Landlord has previously applied any portion
     thereof Tenant has not restored the Security Deposit account to its full
     amount, then on the third (3rd) anniversary of the Commencement Date
     Landlord and Tenant agree that the Security Deposit shall be reduced by
     $51,792.00 from $155,375.00 to $103,583.00 and to effectuate such reduction
     (i) Tenant shall deliver to Landlord a new Letter of Credit (complying with
     the foregoing requirements) in the amount of $103,583.00 which shall stand
     as the Security Deposit under this Lease and (ii) promptly thereafter
     Landlord shall return the existing Letter of Credit to Tenant.

     If Landlord conveys Landlord's interest under this Lease, the Security
     Deposit, or any part thereof not previously applied or returned, may be
     turned over by Landlord to Landlord's grantee, and, if so turned over,
     Tenant agrees to look solely to such grantee for proper application of the
     Security Deposit in accordance with the terms of this Section 8.20, and the
     return thereof in accordance herewith provided that Landlord gives Tenant
     written notice of such transfer of the Security Deposit to Landlord's
     grantee.

     Neither the holder of any mortgage nor the lessor in any ground lease on
     property which includes the Premises shall ever be responsible to Tenant
     for the return or application of the Security Deposit, or portion thereof
     not previously applied or returned, whether or not it succeeds to the
     position of Landlord hereunder, unless the Security Deposit, or portion

                                      -68-
<PAGE>
                                                                    Exhibit 10.9
     thereof not previously applied or returned, shall have been received in
     hand by such holder or ground lessor.

8.21 If Landlord shall not have received any payment or installment of rent
     within five (5) days the date (the "Due Date") on which the same first
     becomes payable under this Lease, the amount of such payment or installment
     shall bear interest from the Due Date through and including the date such
     payment or installment is received by Landlord, at a rate equal to the
     lesser of (i) the rate announced by The First National Bank of Boston from
     time to time as its prime or base rate (or if such rate is no longer
     available, a comparable rate reasonably selected by Landlord), plus two
     percent (2%), or (ii) the maximum applicable legal rate, if any.  Such
     interest shall be deemed Additional Rent and shall be paid by Tenant to
     Landlord upon demand.

8.22 Provided and only so long as (i) there shall not have occurred an Event of
     Default (as defined in Section 7.1, (ii) this Lease is in full force and
     effect and (iii) Tenant has neither assigned this Lease nor sublet more
     than twenty five percent (25%) of the Rentable Floor Area of the Premises
     (except for an assignment or subletting permitted under Section 5.6.1
     hereof), Landlord hereby agrees not to grant signage rights (other than
     signage located within the Building and a directory sign listing
     substantially all of the tenants in the Building as reasonably determined
     by Landlord) to any one (1) tenant leasing less than fifty thousand
     (50,000) square feet of rentable floor area in the Building (including
     expansion options) without granting to Tenant similar signage rights as
     determined by Landlord in its reasonable judgment.

     In the event that, pursuant to the foregoing paragraph, Landlord shall
     grant signage rights to Tenant, (i) the location, size, design and all
     other aspects and features of such sign and its erection and construction
     proposed by Tenant shall be subject to Landlord's approval not to be
     unreasonably withheld or delayed, (ii) Tenant's right to install such sign
     shall be subject to (a) the provisions of the Town of Lexington Zoning By-
     Law and other laws, by-laws, rules and regulations from time to time in
     effect and applicable and (b) Tenant obtaining and delivering to Landlord
     prior to erecting such sign and thereafter maintaining in full force and
     effect all permits, licenses and approvals respecting such sign
     (collectively "Sign Permits") at Tenant's sole cost and expense; and (iii)
     any such signage so approved by Landlord and for which Sign Permits have
     been issued shall be erected in a good and workmanlike manner, and shall be
     maintained by Tenant in good order and condition throughout the Lease Term
     and on the expiration or earlier termination of the Lease Term shall, at
     Landlord's sole election, be removed by Tenant with Tenant restoring the
     area and repairing any damage caused or resulting from such removal, all of
     the foregoing to be done, performed and observed at Tenant's sole cost and
     expense.

                                      -69-
<PAGE>

                                                                    Exhibit 10.9
     Tenant acknowledges, covenants and agrees that it only has right to signage
     on the limited terms and conditions set forth in the preceding two (2)
     paragraphs.  The failure or inability of Tenant to obtain Landlord's
     approval hereunder and/or to obtain any Sign Permits or to otherwise comply
     with or satisfy the requirements of this Section shall not constitute a
     default of Landlord, shall not give Tenant any right to terminate this
     Lease and shall not give Tenant any right to any setoff, abatement or other
     reduction in Annual Fixed Rent or any Additional Rent.

     In the event Landlord, in its sole discretion, shall erect a monument type
     sign identifying tenants of the Building, Landlord shall include Tenant's
     name thereon.

8.23 Landlord shall use its best efforts to make arrangements with a third party
     contractor (the "Cafeteria Operator") for the operation of a cafeteria in
     the Building's common area during the Term of this Lease Monday through
     Friday from 7:00 A.M. to 11:00 A.M. and 11:30 A.M. TO 1:30 P.M. (except
     Saturdays, Sundays and holidays).  The menu and method of operation shall
     be as determined by the Cafeteria Operator.

     Such cafeteria shall be for the use only of Tenant and other tenants,
     subtenants (and occupants) from time to time in the Building and their
     respective employees and business invitees as ancillary to the use of the
     Premises and other tenants', subtenants' (or occupants') premises for the
     conduct of the Permitted Use of Tenant and the permitted uses of such other
     tenants, subtenants (and occupants).  In no event shall the cafeteria be
     open to the general public.  Notwithstanding the foregoing, the operation
     of the cafeteria shall be subject to Landlord and the Cafeteria Operator
     obtaining and maintaining in full force and effect all licenses, permits,
     special permits, approvals and the like as shall be required pursuant to
     applicable governmental requirements respecting the use and operation of a
     cafeteria (collectively the "Cafeteria Approvals").  Landlord shall use
     best efforts to obtain or cause the Cafeteria Operator to obtain the
     Cafeteria Approvals.  However, the failure of Landlord and/or the Cafeteria
     Operator to obtain and/or maintain the Cafeteria Approvals and/or to
     operate the Cafeteria shall not affect this Lease in any way and, without
     limitation, Tenant shall have no right to terminate this Lease and shall
     have no right to any abatement or other reduction of Annual Fixed Rent or
     Additional Rent.

                                      -70-
<PAGE>

                                                                    Exhibit 10.9
     All of the costs incurred in the operation, maintenance and repair of the
     Cafeteria including, but not limited to, the cost of electricity and other
     utilities to and for the Cafeteria, repairs, maintenance of equipment,
     insurance premiums respecting any insurance covering the Cafeteria
     operation, costs of permit, approval and license applications, renewals and
     similar charges, cleaning of the Cafeteria area and trash removal incurred
     in the operation of the Cafeteria shall be included in "Landlord's
     Operating Expenses" referred to in Section 2.6 (collectively the "Cafeteria
     Operating Expenses").

8.24 This Lease shall be governed exclusively by the provisions hereof and by
     the law of the Commonwealth of Massachusetts, as the same may from time to
     time exist.

     EXECUTED as a sealed instrument in two or more counterparts each of which
shall be deemed to be an original.

                                       LANDLORD:


WITNESS:                               By
                                         -----------------------------------
                                         EDWARD H. LINDE, AS TRUSTEE OF
                                         91 HARTWELL AVENUE TRUST FOR
--------------------------               HIMSELF AND CO-TRUSTEE BUT NOT
                                         INDIVIDUALLY



                      (Signatures continued on next page.)

                                      -71-
<PAGE>
                                                                    Exhibit 10.9
                                       TENANT:

                                       WORKGROUP TECHNOLOGY CORPORATION


                                       By
                                         -------------------------------------
                                       Name
                                           -----------------------------------
ATTEST:                                Title   PRESIDENT (OR VICE PRESIDENT)
                                            ----------------------------------
                                       HERETO DULY AUTHORIZED

---------------------------------
Name
    -----------------------------      By
Title  Secretary                         -------------------------------------
     ----------------------------      Name
       (Assistant Secretary)               -----------------------------------
                                       Title TREASURER    
                                            ----------------------------------
                                             (OR ASSISTANT TREASURER)
                                            ----------------------------------

                                             HERETO DULY AUTHORIZED

                                                   (CORPORATE SEAL)

 

                                      -72-
<PAGE>
 
                                                                    Exhibit 10.9
                                   EXHIBIT A
                                   ---------


     That certain parcel of land situate in Lexington in the County of Middlesex
and Commonwealth of Massachusetts, described as follows:

          SOUTHEASTERLY  by Hartwell Avenue, two hundred thirty-seven and 47/100
                         feet;

          SOUTHEASTERLY  by a curving line forming the junction of said Hartwell
                         Avenue and Hartwell Place, as shown on plan hereinafter
                         mentioned, thirty-nine and 27/100 feet;

          SOUTHWESTERLY  five hundred thirty-two and 23/100 feet, and

          SOUTHWESTERLY, SOUTHERLY and SOUTHEASTERLY one hundred ninety and
          25/100 feet, by said Hartwell Place;

          SOUTHERLY  by lot 9 on said plan, three hundred seventy-four and
                         57/100 feet;

          SOUTHWESTERLY  three hundred sixty-seven and 65/100 feet;

          NORTHWESTERLY thirty-one and 12/100 feet, and

          NORTHWESTERLY again, eight hundred ninety and 63/100 feet, by land now
                                            or formerly of The United States of 
                        America;

          NORTHEASTERLY  by said United States of America land and by land now
                         or formerly of John W. O('Connor et al, nine hundred
                         thirty-three and 87/100 feet.

     Said parcel is shown as lot 10 on said plan, (Plan No.31330/D/).

     All of said boundaries are determined by the Court to be located as shown
on a subdivision plan, as approved by the Court, filed in the Land Registration
Office, a copy of which is filed in the Registry of Deeds for the South Registry
District of Middlesex County in Registration Book 835, Page 146, with
Certificate 141096.

     The above described land is subject to and has the benefit of the ditches
as approximately 

                                      -73-
<PAGE>

                                                                    Exhibit 10.9
shown on said plan at date of original decree, (May 17, 1963).

                                      -74-
<PAGE>
 
                                                                    Exhibit 10.9
     So much of the above described land as is included within the area marked
"Tennessee Gas Transmission Company Easement 30' wide" is subject to the
easements set forth in a taking by the Northeastern Gas Transmission Company,
dated July 13, 1951 and duly recorded in
Book 7772, Page 162.

     The above described land is subject to an Avigation Easement set forth in a
Declaration of Taking by the United States of America dated February 12, 1954
recorded with the Middlesex South District Registry of Deeds in Book 8219, Page
421 and more particularly shown as "Avigation Easement A-130E-1" on Plan No.
31330-D (referred to above).

     The above described land is subject to an Order by the Town of Lexington
for construction of water main in Hartwell Avenue, Document No. 461902 as
affected by Certificate for Dissolving Betterments filed as Document No. 499500.

     The above described land is subject to a Grant of Easement from Wilbur C.
Nylander et al Trs. to the Town of Lexington to construct and maintain sewer in
Hartwell Place, Document No. 508567.

     The above described land is subject to a grant of Easement over 20 feet
wide drain easement (i) for the benefit of lot 9 in common with others entitled
thereto, set forth in  Document 511666 and (ii) set forth in Document No. 479843
for the benefit of lot 7 shown on plan recorded with said Document No. 479843.

     The above described land is subject to a Taking of easement by the Town of
Lexington in Hartwell Place, Document No. 544200.

     The above described land is subject to and has the benefit of a Grant of
Easement and Reservation from Wilbur C. Nylander et al Trs. to the Town of
Lexington for conservation purposes, Document No. 616453.

     The above described land is subject to and has the benefit of the
following:

          A.   Order of Conditions issued by the Town of Lexington Conservation
               Commission filed as Document No. 616456 as extended by Extension
               Permits issued by said Conservation Commission filed as Document
               Nos. 627154, 635069, 655552 and 669180.

          B.   Decision of the Town of Lexington Board of Appeals filed as
               Document No. 616457.

                                      -75-
<PAGE>
 
                                                                    Exhibit 10.9
          C.   Decision of the Town of Lexington Board of Appeals filed as
               Document No. 616458.

          D.   Decision of the Town of Lexington Board of Appeals filed as
               Document No. 616459.

          E.   Decision of the Town of Lexington Board of Appeals filed as
               Document No. 634489.

          F.   Decision of the Town of Lexington Board of Appeals filed as
               Document No. 646344.

          G.   Decision of the Town of Lexington Board of Appeals filed as
               Document No. 646345.

          H.   Decision of the Town of Lexington Board of Appeals filed as
               Document No. 646346.

     The above described land is subject to an Easement granted to Boston Edison
Company filed as Document No. 672152.

     The above described land is subject to such other easements, agreements and
matters of record, if any, insofar as in force and applicable.

                                      -76-
<PAGE>
 
                                                                    Exhibit 10.9
                                   Exhibit B
                                   ---------

                       Description of Base Building Work


 .    New entry brick walkway into the main entrance of the Building.

 .    General parking lot upgrade, including a new drop off at main entrance.

 .    New lobby improvements.

 .    Cosmetic upgrades to all building common areas including bathrooms,
     elevator cabs and common corridors and stairways.

 .    A new cafeteria.

 .    Showers and lockers in the first floor bathrooms.

                                      -77-
<PAGE>
 
                                                                    Exhibit 10.9
EXHIBIT C
---------

                                 LANDLORD SERVICES


I.  CLEANING:
    ---------

       Cleaning and janitor services as provided below:

       A.    Office Areas:
             -------------

             Daily:  (Monday through Friday, inclusive, holidays excepted).
             ------                                                        

             1.   Empty all waste receptacles and ashtrays and remove waste
                  material from the Premises; wash receptacles as necessary.

             2.   Sweep and dust mop all uncarpeted areas using a dust-treated
                  mop.

             3.   Vacuum all rugs and carpeted areas.

             4.   Hand dust and wipe clean with treated cloths all horizontal
                  surfaces, including furniture, office equipment, window sills,
                  door ledges, chair rails, and convector tops, within normal
                  reach.

             5.   Wash clean all water fountains and sanitize.

             6.   Move and dust under all desk equipment and telephones and
                  replace same (but not computer terminals, specialized
                  equipment or other materials).

             7.   Wipe clean all chrome and other bright work.

             8.   Hand dust grill work within normal reach.

             9.   Main doors to premises shall be locked and lights shut off
                  upon completion of cleaning.

             Weekly:
             -------

             1.   Dust coat racks and the like.

             2.   Spot clean entrance doors, light switches and doorways.

                                      -78-
<PAGE>
 
                                                                    Exhibit 10.9
             Quarterly:
             ----------

             1.   Render high dusting not reached in daily cleaning to include:

                  a)   dusting all pictures, frames, charts, graphs and similar
                       wall hangings.

                  b)   dusting of all vertical surfaces, such as walls,
                       partitions, doors and door frames, etc.

                  c)   dusting all pipes, ducts and moldings.

                  d)   dusting of all vertical blinds.

                  e)   dust all ventilating, air conditioning, louvers and
                       grills.

             2.   Spray buff all resilient floors.


       B.    LAVATORIES:
             -----------

             Daily:  (Monday through Friday, inclusive, holidays excepted).
             ------                                                        

             1.   Sweep and damp mop.

             2.   Clean all mirrors, powder shelves, dispensers and receptacles,
                  bright work, flushometers, piping and toilet seat hinges.

             3.   Wash both sides of all toilet seats.

             4.   Wash all basins, bowls and urinals.

             5.   Dust and clean all powder room fixtures.

             6.   Empty and clean paper towel and sanitary disposal receptacles.

             7.   Remove waste paper and refuse.

             8.   Refill tissue holders, soap dispensers, towel dispensers,
                  sanitary dispensers; materials to be furnished by Landlord.



             Monthly:
             --------

             1.   Machine scrub lavatory floors.

             2.   Wash all partitions and tile walls in lavatories.

                                      -79-
<PAGE>
 
                                                                    Exhibit 10.9

             3.   Dust all lighting fixtures and grills in lavatories.


       C.    MAIN LOBBIES, ELEVATORS, STAIRWELLS AND COMMON CORRIDORS:
             ---------------------------------------------------------

             Daily:  (Monday through Friday, inclusive, holidays excepted).
             ------                                                        

             1.   Sweep and damp mop all floors, empty and clean waste
                  receptacles, dispose of waste.

             2.   Clean elevators, wash or vacuum floors, wipe down walls and
                  doors.

             3.   Spot clean any metal work inside lobbies.

             4.   Spot clean any metal work surrounding building entrance doors.

             5.   Sweep all stairwells and dust handrails.

             Monthly:
             --------
 
             1.   All resilient tile floors in public areas to be spray buffed.

       D.    WINDOW CLEANING:
             ----------------

             All exterior windows shall be washed on the inside and outside
             surfaces no less than three (3) times per year.


II.  HVAC:
     -----

       A.    Heating, ventilating and air conditioning equipment will be
             provided with sufficient capacity to accommodate a maximum
             population density of one (1) person per one hundred fifty (150)
             square feet of useable floor area served, and a combined lighting
             and standard electrical load of 3.0 watts per square foot of
             useable floor area. In the event Tenant introduces into the
             Premises personnel or equipment which overloads the system's
             ability to adequately perform its proper functions, Landlord shall
             so notify Tenant in writing and supplementary system(s) may be
             required and installed by Landlord at Tenant's expense, if within
             fifteen (15) days Tenant has not modified its use so as not to
             cause such overload.

             Operating criteria of the basic system are in accordance with the
             Massachusetts Energy Code and shall not be less than the following:

             i)   Cooling season indoor conditions of not in excess of 78
                  degrees Fahrenheit when outdoor conditions are 91 degrees
                  Fahrenheit drybulb and 73 degrees Fahrenheit wetbulb.

                                      -80-
<PAGE>
 
                                                                    Exhibit 10.9

             ii)  Heating season minimum room temperature of 72 degrees
                  Fahrenheit when outdoor conditions are 6 degrees Fahrenheit
                  drybulb.

       B.    Landlord shall provide heating, ventilating and air conditioning as
             normal seasonal charges may require during Normal Building
             Operating Hours (8:00 a.m. to 6:00 p.m., Monday through Friday, and
             8:00 a.m. to 1:00 p.m. on Saturdays, legal holidays in all cases
             excepted).

             If Tenant shall require air conditioning (during the air
             conditioning season) or heating or ventilating during any season
             outside Normal Building Operating Hours, Landlord shall use
             landlord's best efforts to furnish such services for the area or
             areas specified by written request of Tenant delivered to the
             Building Superintendent or the Landlord before 3:00 p.m. of the
             business day preceding the extra usage. For such services, Tenant
             shall pay Landlord, as additional rent, upon receipt of billing, a
             sum equal to the cost incurred by Landlord.

III.  ELECTRICAL SERVICES:
      --------------------

       A.    Landlord shall provide electric power for a combined load of 3.0
             watts per square foot of useable area for lighting and for office
             machines through standard receptacles for the typical office space.

       B.    Landlord, at its option, may require separate metering and direct
             billing to Tenant for the electric power required for any special
             equipment (such as computers and reproduction equipment) that
             requires either 3-phase electric power or any voltage other than
             120, or for any other usage in excess of 3.0 watts per square foot.

       C.    Landlord will furnish and install, at Tenant's expense, all
             replacement lighting tubes, lamps and ballasts required by Tenant.
             Landlord will clean lighting fixtures on a regularly scheduled
             basis at Tenant's expense.

IV.  ELEVATORS:
     ----------

       Provide passenger elevator service.

V.  WATER:
    ------

       Provide hot water for lavatory purposes and cold water for drinking,
       lavatory and toilet purposes.

VI.  CARD ACCESS SYSTEM:
     -------------------

       Landlord will provide a card access system at one entry door of the
       building.

                                      -81-
<PAGE>
 
                                                                    Exhibit 10.9

                                      -82-
<PAGE>
 
                                                                    Exhibit 10.9

                                   EXHIBIT E
                                   ---------

              DECLARATION AFFIXING THE COMMENCEMENT DATE OF LEASE
              ---------------------------------------------------


     THIS AGREEMENT made this ____ day of ___________, 1996, by and between
MORTIMER B. ZUCKERMAN AND EDWARD H. LINDE, TRUSTEES OF 91 HARTWELL AVENUE TRUST
under Declaration of Trust dated September 28, 1981 filed the Middlesex South
Registry District of the Land Court as Document No. 616453 as amended by
instruments dated December 10, 1984 and April 17, 1991 respectively filed with
said Registry District as Document Nos. 675674 and 844541 but not individually
(hereinafter "Landlord") and WORKGROUP TECHNOLOGY __________       (hereinafter
"Tenant").


                        W I T N E S S E T H  T H A T :
                        - - - - - - - - - -  - - - - -

     1.  This Agreement is made pursuant to Section 2.4 of that certain Lease
dated May __, 1996 between the parties aforenamed as Landlord and Tenant (the
"Lease").

     2.  It is hereby stipulated that the Lease Term commenced on ____________
__, 1996, (being the "Commencement Date" under the Lease), and shall end and
expire on ___________ __, 2001__, unless sooner terminated or extended, as
provided for in the Lease.

     3.  Tenant hereby acknowledges and agrees with Landlord that on the
Commencement Date the Premises complied with all of the requirements of Article
III of the Lease and that the Landlord satisfied all of its obligations under
said Article III. [NOTE: IF, AT THE TIME THIS INSTRUMENT IS EXECUTED, LANDLORD
HAS NOT COMPLETED THE PUNCH LIST ITEMS OR LONG LEAD ITEMS THIS FACT IS TO BE SO
SPECIFIED.]

     WITNESS the execution hereof under seal by persons hereunto duly
authorized, the date first above written.

WITNESS:                       LANDLORD:


-----------------              ------------------------------------------------
                               EDWARD H. LINDE, AS TRUSTEE OF
                               91 HARTWELL AVENUE TRUST FOR HIMSELF 
                               AND CO-TRUSTEE, BUT NOT INDIVIDUALLY

                                      -83-
<PAGE>
 
                                                                    Exhibit 10.9

                       Signatures continued on next page

                                      -84-
<PAGE>
                                                                    Exhibit 10.9
                               TENANT:
                               WORKGROUP TECHNOLOGY CORPORATION
ATTEST:

                               By:
                                  ----------------------------------------------
-------------------------      Name:
Name:                               --------------------------------------------
     --------------------      Title:
Title:                               -------------------------------------------
      -------------------            HEREUNTO DULY AUTHORIZED 


                                            (CORPORATE SEAL)



                         COMMONWEALTH OF MASSACHUSETTS


COUNTY OF SUFFOLK                                     ________ ___, 1996


    Then personally appeared before me the above-named Edward H. Linde, Trustee
as aforesaid, and made oath that the foregoing instrument is his free act and
deed.


                                      ---------------------------------------
                                      NOTARY PUBLIC

                                      My Commission Expires:

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

                                      -85-
<PAGE>
 
                                                                    Exhibit 10.9
                         COMMONWEALTH OF MASSACHUSETTS


COUNTY OF _____________                         _______ ___, 1996


    Then personally appeared before me the above-named _______________, the
________________, of WORKGROUP TECHNOLOGY CORPORATION and acknowledged the
foregoing instrument to be the free act and deed of said corporation.


                                      ----------------------------------------
                                      NOTARY PUBLIC

                                      My Commission Expires:

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

                                      -86-
<PAGE>
 
                                                                    Exhibit 10.9
                                   EXHIBIT G
                                   ---------
 
                BROKER DETERMINATION OF PREVAILING MARKET RENT
                ----------------------------------------------
 

     Where in the Lease to which this Exhibit is attached provision is made for
a Broker Determination of Prevailing Market Rent, the following procedures and
requirements shall apply:

1.   Tenant's Request.  Tenant shall send a notice to Landlord by the time set
     ----------------                                                         
     for such notice in the applicable section of the Lease, requesting a Broker
     Determination of the Prevailing Market Rent, which notice to be effective
     must (i) make explicit reference to the Lease and to the specific section
     of the Lease pursuant to which said request is being made, (ii) include the
     name of a broker selected by Tenant to act for Tenant, which broker shall
     be affiliated with a major Boston commercial real estate brokerage firm
     selected by Tenant and which broker shall have at least ten (10) years
     experience dealing in properties of a nature and type generally similar to
     the Building located in the Boston West Suburban Market, and (iii)
     explicitly state that Landlord is required to notify Tenant within twenty
     (20) days of an additional broker selected by Landlord.

2.   Landlord's Response.  Within twenty (20) days after Landlord's receipt of
     -------------------                                                      
     Tenant's notice requesting the Broker Determination and stating the name of
     the broker selected by Tenant, Landlord shall give written notice to Tenant
     of Landlord's selection of a broker having at least the affiliation and
     experience referred to above.

3.   Selection of Third Broker.  Within ten (10) days thereafter the two (2)
     -------------------------                                              
     brokers so selected shall select a third such broker also having at least
     the affiliation and experience referred to above.

4.   Rental Value Determination.  Within thirty (30) days after the selection of
     --------------------------                                                 
     the third broker, the three (3) brokers so selected, by majority opinion,
     shall make a determination of the annual fair market rental value of the
     Premises for the period referred to in the Lease.  Such annual fair market
     rental value determination (x) may include provision for annual increases
     in rent during said term if so determined, (y) shall take into account the
     as-is condition of the Premises and (z) shall take account of, and be
     expressed in relation to, the tax and operating cost bases and provisions
     for paying for so-called tenant electricity as contained in the Lease.  The
     brokers shall advise Landlord and Tenant in writing by the expiration of
     said thirty (30) day period of the annual fair market rental value which as
     so determined shall be referred to as the Prevailing Market Rent.

5.   Resolution of Broker Deadlock.  If the Brokers are unable to agree at least
     -----------------------------                                              
     by majority on 

                                      -87-
<PAGE>
 
                                                                    Exhibit 10.9
     a determination of annual fair market rental value, then the brokers shall
     send a notice to Landlord and Tenant by the end of the thirty (30) day
     period for making said determination setting forth their individual
     determinations of annual fair market rental value, and the highest such
     determination and the lowest such determination shall be disregarded and
     the remaining determination shall be deemed to be the determination of
     annual fair market rental value and shall be referred to as the Prevailing
     Market Rent.

6.   Costs.  Each party shall pay the costs and expenses of the broker selected
     -----                                                                     
     by it and each shall pay one half (1/2) of the costs and expenses of the
     Third Broker.

7.   Failure to Select Broker or Failure of Broker to Serve.  If Tenant shall
     ------------------------------------------------------                  
     have requested a Broker Determination and Landlord shall not have
     designated a broker within the time period provided therefor above, then
     Tenant's Broker shall alone make the determination of Prevailing Market
     Rent in writing to Landlord and Tenant within thirty (30) days after the
     expiration of Landlord's right to designate a broker hereunder.  If Tenant
     and Landlord have both designated brokers but the two brokers so designated
     do not, within a period of ten (10) days after the appointment of the
     second broker, agree upon and designate the Third Broker willing so to act,
     the Tenant, the Landlord or either broker previously designated may within
     ten (10) days after the expiration of said ten (10) day period request the
     Greater Boston Real Estate Board, Inc. (herein called the "Real Estate
     Board") to designate the Third Broker willing so to act and a broker so
     appointed shall, for all purposes, have the same standing and powers as
     though he had been timely appointed by the brokers first appointed.  Such
     broker shall be appointed within ten (10) days after the Board's receipt of
     such a report.  In case of the inability or refusal to serve of any person
     designated as a broker, or in case any broker for any reason ceases to be
     such, a broker to fill such vacancy shall be appointed by the Tenant, the
     Landlord, the brokers first appointed or the Real Estate, as the case may
     be, whichever made the original appointment, or if the person who made the
     original appointment fails to fill such vacancy, upon application (made
     within five (5) days after the event necessitating such application) of any
     broker who continues to act or by the Landlord or Tenant such vacancy may
     be filled by the Real Estate Board and any broker so appointed to fill such
     vacancy shall have the same standing and powers as though originally
     appointed provided such vacancy is filled within ten (10) days after such
     vacancy otherwise the foregoing provisions will apply.

                                      -88-
<PAGE>
 
                                                                    Exhibit 10.9
                                   EXHIBIT H
                                   ---------

            SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT


          THIS AGREEMENT is made as of this ______ day of ____________, 1996 by
and among CONNECTICUT GENERAL LIFE INSURANCE COMPANY, a Connecticut corporation
having its principal office and place of business at 900 Cottage Grove Road,
Bloomfield, Connecticut 06002 ("Lender"), MORTIMER B. ZUCKERMAN and EDWARD H.
LINDE as Trustees of 91 HARTWELL AVENUE TRUST under Declaration of Trust dated
September 28, 1981 filed with the Middlesex South Registry District as Document
No. 616455 as amended by instruments dated December 10, 1984 and April 17, 1991
respectively filed with said Registry District as Document Nos. 675674 and
844541,but not individually, whose address is c/o Boston Properties, 8
Arlington Street, Boston, Massachusetts 02116 ("Landlord), and WORKGROUP
TECHNOLOGY CORPORATION, a Delaware corporation ("Tenant").



                                  WITNESSETH:

     WHEREAS, Tenant has entered into a certain lease (the "Lease") dated July
__, 1996  with Landlord covering premises (the "Premises") within a certain
building known as 91 Hartwell Avenue located in the Town of Lexington,
Middlesex County, Massachusetts on the real property more particularly described
in Exhibit "A" attached hereto and incorporated herein; and

          WHEREAS, Lender has made a loan (the "Loan") to Landlord which is
evidenced by a promissory note issued by Landlord to Lender (the "Note") and
secured by a Mortgage and Security Agreement (the "Mortgage") and by an
Assignment of Rents and Leases (the "Assignment") encumbering, inter alia, the
Premises; and

          WHEREAS, Tenant acknowledges that the recorded Mortgage constitutes a
lien or charge upon the Premises which is unconditionally prior and superior to
the Lease and the leasehold interest of Tenant thereunder; and

          WHEREAS, Lender has been requested by Tenant and by Landlord to enter
into a non-disturbance agreement with Tenant;

          NOW, THEREFORE, in consideration of the premises and mutual covenants
hereinafter contained, the parties hereto mutually covenant and agree as
follows:

                                      -89-
<PAGE>
 
                                                                    Exhibit 10.9
1.   The Lease and any extensions, renewals, replacements or modifications
     thereof, and all of the right, title and interest of Tenant thereunder in
     and to the Premises are and shall be subject and subordinate to the
     Mortgage and to all of the terms and conditions contained therein, and to
     any renewals, modifications, replacements consolidations and extensions
     thereof.

2.   Lender consents to the Lease and in the event Lender comes into possession
     of or acquires title to the Premises as a result of the foreclosure or
     other enforcement of Mortgage or the Note, or as a result of any other
     means, Lender agrees that, so long as Tenant is not then in default
     hereunder or under the Lease beyond applicable cure periods,  Lender will
     recognize the Lease and will not disturb Tenant in its possession of the
     Premises for any reason other than one which would entitle Landlord to
     terminate the Lease under its terms or would cause, without any further
     action by Landlord, the termination of the Lease or would entitle Landlord
     to dispossess Tenant from the Premises.

3.   Tenant agrees with Lender that if the interests of Landlord in the Premises
     shall be transferred to and owned by Lender by reason of foreclosure or
     other proceedings brought by it, or any other manner, or shall be conveyed
     thereafter by Lender or shall be conveyed pursuant to a foreclosure sale of
     the Premises, Tenant shall be bound to Lender under all of the terms,
     covenants and conditions of the Lease for the balance of the term thereof
     remaining and any extensions or renewals thereof which may be effected in
     accordance with any option therefor in the Lease, with the same force and
     effect as if Lender were the landlord under the Lease, and Tenant does
     hereby attorn to Lender as its landlord, said attornment to be effective
     and self-operative without the execution of any further instruments on the
     part of any of the parties hereto immediately upon Lender succeeding to the
     interest of Landlord in the Premises.  Tenant agrees, however, upon the
     election of and written demand by Lender within twenty (20) days after
     Lender receives title to the Premises, to execute an instrument in
     confirmation of the foregoing provisions, satisfactory to Lender, in which
     Tenant shall acknowledge such attornment and shall set forth the terms and
     conditions of its tenancy.

4.   Tenant agrees with Lender that if Lender shall succeed to the interest of
     Landlord under the Lease, Lender shall not be (a) liable for any action or
     omission of any prior landlord under the Lease, or (b) subject to any
     offsets or defenses which Tenant might have against any prior landlord, or
     (c) bound by any rent or additional rent which Tenant might have paid for
     more than the current month to any prior landlord, or (d) bound by any
     security deposit which Tenant may have paid to any prior landlord, unless
     such deposit is in an escrow fund available to Lender, or (e) bound by any
     amendment or modification of the 

                                      -90-
<PAGE>
 
                                                                    Exhibit 10.9
     Lease made without Lender's written consent, or (f) bound by any notice of
     termination given by Landlord to Tenant without Lender's written consent
     thereto, or (g) personally liable under the Lease and Lender's liability
     under the Lease shall be limited to the ownership interest of Lender in the
     Premises.

5.   In the event that Landlord shall default in the performance or observance
     of any of the terms, conditions or agreements in the Lease, Tenant shall
     give written notice thereof to Lender and Lender shall have the right (but
     not the obligation) to cure such default.  Tenant shall not take any action
     with respect to such default under the Lease, including, without
     limitation, any action in order to terminate, rescind or void the Lease or
     to withhold any rental thereunder, for a period of 10 days after receipt of
     such written notice by Lender with respect to any such default capable of
     being cured by the payment of money and for a period of 30 days after
     receipt of such written notice by Lender with respect to any other such
     default (provided that in the case of any default which cannot be cured by
     the payment of money and cannot with diligence be cured within such 30-day
     period because of the nature of such default or because Lender requires
     time to obtain possession of the Premises in order to cure the default, if
     Lender shall proceed promptly to attempt to obtain possession of the
     Premises, where possession is required, and to cure the same and thereafter
     shall prosecute the curing of such default with diligence and continuity,
     then the time within which such default may be cured shall be extended for
     such period as may be necessary to complete the curing of the same with
     diligence and continuity).

6.   Landlord has agreed in the Mortgage and in the Assignment that the rentals
     payable under the Lease shall be paid directly by Tenant to Lender upon the
     occurrence of a default by Landlord under the Mortgage.  Accordingly, after
     notice is given by Lender to Tenant that the rentals under the Lease should
     be paid to Lender, Tenant shall pay to Lender, or in accordance with the
     directions of Lender, all rentals and other moneys due and to become due to
     Landlord under the Lease, or amounts equal thereto.  Tenant shall have no
     responsibility to ascertain whether such demand by Lender is permitted
     under the Mortgage or the Assignment.  Landlord hereby waives any right,
     claim or demand it may now or hereafter have against Tenant by reason of
     such payment to Lender, and any such payment to Lender shall discharge the
     obligations of Tenant to make such payment to Landlord.

7.   Tenant declares, agrees and acknowledges that:

     a.   Lender, in making disbursements pursuant to any agreement relating to
          the Loan, is under no obligation or duty to, nor has Lender
          represented that it will, see to the application of such proceeds by
          the person or persons to whom Lender disburses such proceeds, and any
          application or use of such proceeds other than those provided for in
          such agreement shall not defeat the subordination herein made in 

                                      -91-
<PAGE>
 
                                                                    Exhibit 10.9
          whole or in part; and

     b.   it intentionally and unconditionally subordinates the Lease and its
          leasehold interest thereunder in favor of the lien or charge upon said
          land of the Mortgage, and that in consideration of this subordination,
          specific loans and advances are being and will be made by Lender to
          Landlord and, as part and parcel thereof, specific monetary and other
          obligations are being and will be entered into by Landlord and Lender
          which would not be made or entered into but for said reliance upon
          this subordination.

8.   This agreement shall bind and inure to the benefit of the parties hereto,
     their successors and assigns.  As used herein, the term "Tenant" shall
     include Tenant, its successors and assigns; the words "foreclosure" and
     "foreclosure sale" as used herein shall be deemed to include the
     acquisition of Landlord's estate in the Premises by voluntary deed (or
     assignment) in lieu of foreclosure; and the word "Lender" shall include the
     Lender herein specifically named and any of its successors, participants
     and assigns, including but not limited to anyone who shall have succeeded
     to Landlord's interest in the Premises by, through or under foreclosure of
     the Mortgage and any purchaser at or subsequent to foreclosure.

9.   All notices, consents and other communications pursuant to the provisions
     of this Agreement shall be in writing and shall be sent by registered or
     certified mail, return receipt requested, or by a reputable commercial
     overnight carrier that provides a receipt, such as Federal Express or
     Airborne, and shall be addressed as follows and shall be deemed given when
     received except where delivery is refused in which case notice shall be
     deemed given on the date delivery is first attempted and refused:

     If to Lender:                  CIGNA Investments, Inc.
                                    c/o CIGNA Investment Group
                                    900 Cottage Grove Road
                                    Bloomfield, Connecticut 06002
                                    Attn:  Real Estate Investment Services

     with a copy to:                CIGNA Corporation
                                    900 Cottage Grove Road
                                    Bloomfield, Connecticut 06002
                                    Attn:  Investment Law Dept.

     If to Tenant:                  Workgroup Technology Corporation
                                    91 Hartwell Avenue
                                    Lexington, Massachusetts 02173

                                      -92-
<PAGE>
 
                                                                    Exhibit 10.9
                                    Attention: Chief Financial Officer

                                      -93-
<PAGE>
 
                                                                    Exhibit 10.9
     If to Landlord:            ------------------------------
                                    c/o Boston Properties
                                    8 Arlington Street
                                    Boston, Massachusetts  02116

     or to such other address as shall from time to time have been designated by
     written notice by such party to the other parties as herein provided.

10.  This Agreement shall be the whole and only agreement between the parties
     hereto with regard to the subordination of the Lease and the leasehold
     interest of Tenant thereunder to the lien or charge of the Mortgage in
     favor of Lender, and shall supersede and control any prior agreements as to
     such, or any, subordination, including, but not limited to, those
     provisions, if any, contained in the Lease, which provide for the
     subordination of the Lease and the leasehold interest of Tenant thereunder
     to a deed or deeds of trust or to a mortgage or mortgages to be thereafter
     executed, and shall not be modified or amended and no provision herein
     shall be waived except in writing signed by the party against whom
     enforcement of any such modification or amendment is sought.

     The use of the neuter gender in this Amendment shall be deemed to include
     any other gender, and words in the singular number shall be held to include
     the plural, when the sense requires. In the event any one or more of the
     provisions of this Agreement shall for any reason be held to be invalid,
     illegal or unenforceable in any respect, such validity, illegality or
     unenforceability shall not affect any other provision of this Agreement,
     but this Agreement shall be construed as if such invalid, illegal or
     unenforceable provision had never been contained herein.  This Agreement
     shall be governed by and construed in accordance with the laws of the State
     of Massachusetts.

     IN WITNESS WHEREOF the parties hereto have placed their hands and seals the
day and year first above written.

Signed and acknowledged in the
presence of us:               TENANT:

                              WORKGROUP TECHNOLOGY                 
                              CORPORATION

------------------------
      By:
         -------------------------
Typed Name:                   Typed Name:
                              Title:

------------------------         Attest:
Typed Name:                             -------------------

                                      -94-
<PAGE>
 
                                                                    Exhibit 10.9
                                   LANDLORD:

                              -------------------------
                                                       Edward H. Linde, 
                       as Trustee of Mall Road Trust,
                              but not individually

                              Attest:
                                     ------------------ 

                              LENDER:

                              CONNECTICUT GENERAL LIFE
                              INSURANCE COMPANY

                              By CIGNA Investments, Inc.


----------------------------       
      By:
         --------------------------
Typed Name:                   Typed Name:
                              Title:

----------------------------      
      Attest:
             -----------------------
  Typed Name:

                                      -95-