Exhibit 10.25

                                   LEASE dated

                                November 14, 1996


                                    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:                             Nashoba View Associates, LLC, a
                                      Massachusetts limited liability company

LANDLORD'S ORIGINAL ADDRESS:          c/o The Chiofaro Company, Inc.
                                      One International Place
                                      Boston, Massachusetts  02110

TENANT:                               Cascade Communications Corp., a
                                      Delaware corporation

TENANT'S ORIGINAL ADDRESS:            5 Carlisle Road
                                      Westford, Massachusetts

TENANT AREA B
PLAN DELIVERY DATE:                   June 27, 1997

CONTINGENCY ALLOWANCE:                $200,000, provided by Landlord

CONSTRUCTION BUDGET:                  $ 4,011,627

TERM:                                 See Section 2.4

TERM COMMENCEMENT DATE:               The date hereof

AREA A COMMENCEMENT DATE:             See Section 2.4





<PAGE>


ESTIMATED AREA A
COMMENCEMENT DATE:                    March 2, 1997

AREA B COMMENCEMENT DATE:             See Section 2.4

ESTIMATED AREA B
COMMENCEMENT                          DATE  November 1, 1997 or if earlier,  the
                                      date 126 days after  delivery  to Landlord
                                      of the Area B Plans  pursuant  to  Section
                                      3.2

INITIAL TERM:                         The portion of the Term beginning on
                                      the Term Commencement Date and ending
                                      on the Initial Term Expiration Date.

INITIAL TERM EXPIRATION DATE:         The last day of the 144th full calendar
                                      month following the Area A Commencement
                                      Date.

EXTENSION TERMS:                      See Section 2.4.1

ANNUAL FIXED RENT:                    Initial Term:
                                      ------------

                                      An  annual  rate  equal  to the sum of (i)
                                      $7.98 per square  foot of  Rentable  Floor
                                      Area of the  Premises  from  time to time,
                                      plus (ii) only  during the period from May
                                      1, 1997  through  the Area B  Commencement
                                      Date,  $5.67 per square  foot of  rentable
                                      floor area of those portions of Area B not
                                      included  in the  Premises  from  time  to
                                      time.


                                      Extension Terms:
                                      ---------------

                                      Annual  Fixed Rent  during  the  Extension
                                      Terms  shall  be  as   established   under
                                      Section 2.4.1.

RENT COMMENCEMENT DATE:               The date Landlord tenders the first
                                      portion of the Premises in accordance
                                      with Section 2.1.1.

LAND:                                 The land described in EXHIBIT B hereto.

BUILDING:                             The building on the Land containing
                                      approximately 278,775 square feet of
                                      rentable floor area with an address of
                                      One Technology Way, Westford,
                                      Massachusetts.  The Building includes
                                      three areas:




                                       

<PAGE>

                                      Area A: 166,551 square feet of rentable
                                      floor area in two stories, including a
                                      mezzanine.

                                      Area B: 92,300 square feet of rentable
                                      floor area in three stories, currently
                                      leased to Concurrent Computer
                                      Corporation.

                                      Area C: 19,924 square feet of rentable
                                      floor area in a high bay warehouse.

      The parties hereby agree that the foregoing  square  footage  measurements
shall be binding for the purpose of this Lease.

PREMISES:                             Prior to the Area A Commencement Date,
                                      or the Area B Commencement Date, as the
                                      case may be, those portions of Area A
                                      and/or Area B that Tenant occupies from
                                      time to time for the conduct of its
                                      business (and not for the purposes of
                                      preparing Area A or Area B for Tenant's
                                      use and occupancy); provided, however,
                                      as of the Area A Commencement Date, the
                                      Premises shall be deemed to include all
                                      of Area A, and, as of the Area B
                                      Commencement Date, the Premises shall
                                      be deemed to include all of Area A and
                                      Area B;  provided, further, the
                                      Premises are subject to expansion under
                                      Section 2.1.1 of this Lease.

FIRST OFFER SPACE:                    See Section 2.1.2

RENTABLE FLOOR AREA
OF THE PREMISES:                      The rentable floor area of the Premises
                                      from time to time.

RENTABLE FLOOR AREA
OF THE BUILDING                       278,775 square feet

PERMITTED USES:                       Administration, sales and other general
                                      office purposes, research and
                                      development (including without
                                      limitation engineering laboratories),
                                      storage and light manufacturing
                                      (including without limitation design,
                                      assembly, reassembly and testing of
                                      electronic products and components),
                                      provided each such use is permitted





                                      

<PAGE>


                                      by applicable zoning ordinances and other
                                      applicable laws and regulations.


PUBLIC LIABILITY INSURANCE:           $2,000,000 with umbrella of at least
                                      $5,000,000.


LANDLORD'S MANAGING AGENT:            The Chiofaro Company, Inc., or a
                                      successor designated from time to time
                                      by Landlord by written notice to Tenant.

ADDRESS OF LANDLORD'S
MANAGING AGENT:                       One International Place - Suite 4600
                                      Boston, Massachusetts 02110

BROKER:                               See Section 8.7

TENANT'S AUTHORIZED
REPRESENTATIVE:                       Paul E. Blondin or a successor
                                      designated by Tenant's President from
                                      time to time

LANDLORD'S FINISH WORK
REPRESENTATIVE:                       Mark C. Roopenian or a successor
                                      designated by Landlord's Manager from
                                      time to time

      The  following  partial list of  additional  defined terms is provided for
reference only:

ADDITIONAL LAND:                      See Article XII

ARCHITECT:                            See Section 3.2

BUILDING SERVICE AGENTS:              See Section 2.6.3

EVENT OF DEFAULT:                     See Section 7.1

EXCLUSIVE PARKING SPACES:             See Article XII

FAIR MARKET NET RENT:                 See Section 2.4.1

FINANCING PARTY:                      See Section 9.2

FINISH WORK:                          See Section 3.2

GENERAL CONTRACTOR:                   See Section 3.1.1




                                       

<PAGE>

LANDLORD'S TAXES:                     See Section 2.6.3

LANDLORD'S WORK:                      See Section 3.1.1

LEASE YEAR:                           See Section 2.5

OPERATING EXPENSES:                   See Section 2.6.3

PLANS:                                See Section 3.2

PRELIMINARY PLANS:                    See Section 3.2

PUNCHLIST ITEMS:                      See Section 3.2 (e)

SUBSTANTIAL COMPLETION OR
SUBSTANTIALLY COMPLETE:               See Section 3.2 (e)

TENANT AFFILIATE:                     See Section 5.9

TENANT'S PROPORTIONATE
SHARE:                                See Section 2.6.1

TENANT'S REMOVABLE
PROPERTY:                             See Section 5.11


      1.2   EXHIBITS
            --------

      The following is a list of Exhibits attached to this Lease.

EXHIBIT A:  Landlord's Work

EXHIBIT B:  Property Description

EXHIBIT C:  Letter of Credit

EXHIBIT D:  Ground Lease

EXHIBIT E:  Plans of the Premises

EXHIBIT F:  Title Exceptions

EXHIBIT G:  Area A Plans





                                       

<PAGE>

                                   ARTICLE II

                         PREMISES, TERM, RENT, OPERATING
                       EXPENSES AND TAXES AND ELECTRICITY


      2.1   PREMISES AND EXCLUSIONS

      Landlord hereby leases to Tenant,  and Tenant hereby leases from Landlord,
the  Premises,  on the terms and  subject  to the  conditions  set forth in this
Lease.  The Premises  exclude the Land and areas and  facilities of the Building
(i)  outside  of the  perimeter  of the  Premises  as shown on EXHIBIT E or (ii)
within such  perimeter  and  necessary  for use,  exclusively  or in common,  by
Landlord or any other tenant of the Building in  connection  with the  operation
and management of any portion of the Building other than the Premises, including
without  limitation  exterior faces of exterior walls;  any common stairways and
stairwells,  Building  entrance  ways  and  the  ground  floor  Building  lobby,
elevators  and  elevator  wells  necessary  for access to other  portions of the
Building;  any fan rooms,  electric  and  telephone  closets,  janitor  closets,
freight elevator  vestibules (other than those exclusively serving Area A and/or
Area B), and pipes,  ducts,  conduits,  wires and appurtenant  fixtures  serving
other parts of the Building (exclusively or in common with the Premises).

      This Lease is  subject to all  easements,  restrictions,  agreements,  and
encumbrances  listed on Exhibit F attached to this Lease, to the extent in force
and applicable, provided the same shall not interfere with the Permitted Uses.

            2.1.1  DELIVERY OF THE PREMISES.  Landlord  shall notify Tenant when
such Landlord's Work and Finish Work as is reasonably  necessary for the use and
occupancy  of Area A or Area B,  respectively,  are  Substantially  Complete (as
defined in Section 3.2 below).  Landlord  shall tender to Tenant  possession  of
Area A no more than three  business days after  delivering to Tenant such notice
relating to Area A, but no sooner than the Estimated Area A  Commencement  Date,
unless otherwise  specifically  requested by Tenant or otherwise permitted under
this Section 2.1.1 with respect to portions of Area A. Landlord  shall tender to
Tenant possession of Area B no more than three business days after delivering to
Tenant such notice  relating to Area B, but not sooner than the Estimated Area B
Commencement Date unless otherwise specifically requested by Tenant or otherwise
permitted  under this Section  2.1.1 with respect to portions of Area B. If such
Landlord's  Work and  Finish  Work as is  reasonably  necessary  for the use and
occupancy of any portion of Area A or Area B are  Substantially  Complete,  then
(i) prior to the Estimated Area A Commencement Date, with respect to portions of
Area A, and the  Estimated  Area B  Commencement  Date,  with respect to Area B,
Tenant may, by written  notice to  Landlord,  request that  Landlord  deliver to
Tenant  possession  of such portion of Area A or Area B, as the case may be, and
Landlord shall tender possession of such portion to Tenant within three business
days  after  receiving  such  notice  from  Tenant  unless  Landlord  reasonably
determines  that  delivery of such  portion to Tenant would  interfere  with the
completion of the balance of Landlord's  Work or Finish Work; and (ii) after the
Estimated





                                       

<PAGE>

Area A Commencement  Date, with respect to portions of Area A, and the Estimated
Area B Delivery  Date,  with respect to portions of Area B, Landlord may,  three
business  days after notice to Tenant,  tender to Tenant  possession of any such
portion  of Area A or Area B, as the  case  may  be,  and  Tenant  shall  accept
possession of such portion of Area A or Area B unless  Tenant cannot  reasonably
use or occupy such  portion  without a material  interference  with its business
operations.  Nothing in the  foregoing  sentence  shall be  construed  to permit
Tenant to delay  acceptance of Landlord's  tender to Tenant of possession of all
of Area A or Area B, as the case may be, in the condition required hereunder. At
the time of  delivery  thereof to Tenant,  Area A and Area B (or any  portion(s)
thereof) shall be free of all tenants and occupants other than Tenant.


            2.1.2 RIGHT OF FIRST REFUSAL.  During the Term,  Tenant shall have a
right of first  refusal with  respect to Area C,  provided  that (at  Landlord's
election)  (i) no  Event  of  Default  exists  either  at the  time of  Tenant's
acceptance  of the  offer or at the time the First  Offer  Space is added to the
Premises,  and (ii) Tenant will use the space for the  expansion of its business
at the Premises.  If Landlord receives an offer to lease or letter of intent (an
"Offer")  with  respect to Area C from a  prospective  tenant  (the  "Offeree"),
before  accepting such Offer,  Landlord shall offer to lease Area C to Tenant on
the same terms as the Offer by giving  written  notice to Tenant of the terms of
such Offer and the identity of the Offeree.  Tenant shall have 15 business  days
from receipt of such notice from  Landlord to accept  Landlord's  offer to lease
Area C by giving written notice to Landlord.  If Tenant accepts Landlord's offer
to lease Area C, Area C shall be incorporated into the Premises on the terms and
conditions set forth in the Offer (including, without limitation, any provisions
or conditions with respect to finish work to be completed in Area C) and, to the
extent the Offer does not specify terms different from or conflicting  with this
Lease,  the terms and conditions of this Lease,  provided that in the event that
the term of the lease for the First Offer Space  exceeds the Term of this Lease,
(i) Article XII of this Lease  shall not be  construed  to apply to the lease of
the First  Offer  Space for any  period of such  lease  beyond  the Term of this
Lease;  (ii)  Section  2.4.1 shall not be construed to apply to the lease of the
First  Offer  Space  (unless  included  in the  terms of the  Offer);  and (iii)
notwithstanding  anything to the contrary in Section 2.2,  Tenant shall not have
the exclusive right to use the loading platform and the freight elevators within
Areas A and B during such period.  If Tenant fails to accept Landlord's Offer to
lease Area C within such 30-day  period,  Landlord may lease Area C on the terms
and  conditions  of the Offer to the  Offeree  or any  other  party) at any time
during  the  following  180 days.  If  Landlord  wishes to lease Area C on terms
differing materially from the Offer, or if Landlord fails to lease Area C on the
terms set forth in the Offer  within such  180-day  period,  before  executing a
lease with the Offeree or accepting a new Offer,  Landlord  shall again offer to
lease Area C to Tenant in accordance  with this Section 2.1.2.  The term for the
First Offer Space shall  commence on the date  therefor  specified in Landlord's
notice  of offer  and  terminate  at the end of the Term (as it may be  extended
pursuant to the terms  contained  in this Lease) or the earlier  termination  of
this Lease or the earlier date specified in Landlord's notice or where less than
three (3) years remains in the Term,  then at  Landlord's  option for as long as
three (3) years from the first day of the term for the First Offer Space.





                                       

<PAGE>

      2.2   APPURTENANT RIGHTS
            ------------------

      Tenant shall have, as appurtenant to the Premises,  rights for Tenant, its
employees and business invitees to use in common with Landlord and other tenants
of the Building (subject to reasonable rules of general applicability to tenants
and other users of the Building from time to time made by Landlord in accordance
with the terms hereof): (a) any common lobbies, entrances, corridors, stairways,
elevators and loading  platform of the  Building;  any pipes,  ducts,  conduits,
wires, fan rooms,  utility closets,  janitor  closets,  and appurtenant  meters,
fixtures,  and equipment serving the Premises in common with others;  (b) common
parking  areas,  and any  driveways  and  walkways  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 on such floor and
serving  the  Premises;  and (d) all  other  areas  or  facilities  outside  the
perimeter  of the Premises but in or about the Building or on the Land from time
to time intended for general use by Tenant, other Building tenants, and Landlord
(collectively,  the "Common Facilities").  Tenant shall have the exclusive right
to use the loading platform and the freight elevators within Areas A and B.

      2.3   RESERVATIONS
            ------------

      Landlord  reserves  the right  from time to time,  upon  reasonable  prior
notice to Tenant (except in an emergency) and without unreasonable (except in an
emergency)  interruption of Tenant's use of the Premises:  (a) to install,  use,
maintain,  repair,  replace and  relocate  for service to the Premises and other
parts of the Building,  pipes, ducts, conduits,  wires and appurtenant fixtures,
wherever  located in the Premises or Building;  and (b) to alter or relocate any
other Common Facility. Installations, replacements and reallocations referred to
in clause (a) above shall be located as 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   TERM
            ----

      The "Term" of this Lease  includes the Initial  Term,  which begins on the
Term  Commencement  Date  established  under Section 1.1 and ends on the Initial
Term  Expiration  Date set forth in Section  1.1,  together  with all  Extension
Terms.  Landlord  estimates that the Area A Commencement  Date will begin on the
Estimated Area A Commencement  Date.  Landlord  shall use diligent  efforts,  to
cause the Area A  Commencement  Date to occur on or before the Estimated  Area A
Commencement Date. However, in attempting to accomplish the foregoing,  Landlord
shall not be  obligated  to expend  any sums in excess of the  aggregate  of the
Construction   Budget  and  the  Contingency   Allowance  not  included  in  the
Construction  Budget.  Provided  Landlord has exercised  such diligent  efforts,
Landlord's  failure to cause the Area A  Commencement  Date to occur on or about
the Estimated  Area A Commencement  Date,  for any reason,  shall not (except as
provided in the next three  sentences)  give rise to any  liability  of Landlord
hereunder,  shall not  constitute  a  Landlord's  default,  shall not affect the
validity of this Lease,  and shall have no effect on the beginning or end of the
Term as otherwise  determined  hereunder or on Tenant's  obligations  associated
therewith.  If Landlord fails to deliver Area A in the condition required hereby
on or before the Estimated Area A Commencement Date (which






                                       

<PAGE>


deadline  shall be extended by one day for each day of Tenant Delay with respect
to Area A),  Landlord  shall use  reasonable  efforts,  at its sole expense,  to
deliver Area B (or such  portions  thereof as Tenant may request) in  tenantable
condition for Tenant's  temporary use and occupancy for the Permitted Uses until
delivery of Area A in accordance  herewith.  If Landlord fails to deliver Area A
to  Tenant  in the  condition  required  hereby  on or  before  the later of (i)
September  1, 1997 (if there have been no Tenant  Delays) and (ii)  September 1,
1997 plus the number of days of Tenant  Delays,  Tenant  shall have the right to
terminate  this Lease by notice to Landlord  without  recourse to any party.  If
Landlord fails to deliver Area B to Tenant in the condition  required  hereby on
or before the later of (i) January 1, 1998 (if there have been no Tenant Delays)
and (ii) January 1, 1998 plus the number of days of Tenant Delays,  either party
shall  have the right to  terminate  this  Lease by notice to the other  without
recourse  to any  party.  If at any  time it  becomes  apparent  that the Area A
Commencement  Date will not occur on or before the Estimated Area A Commencement
Date (or the Area B Commencement  Date will not occur on or before the Estimated
Area B Commencement Date),  Landlord will so notify Tenant and both parties will
take reasonable  available steps to minimize excess costs and otherwise to avoid
or mitigate losses.

      The Initial Term shall begin at 12:01 a.m. on the Term Commencement  Date,
and shall end at 12:00 midnight on the Term Expiration Date set forth in Section
1.1.

      For the purposes of this Lease,  the "Area A Commencement  Date" means the
first  day that (i)  such  Landlord's  Work  and  Finish  Work as is  reasonably
necessary for the use and occupancy of Area A are  Substantially  Complete,  and
Landlord has delivered to Tenant a certificate from Landlord's architect to that
effect, and (ii) Landlord has tendered  possession of Area A to Tenant,  free of
tenants and occupants;  and the "Area B  Commencement  Date" means the first day
that (i)  Landlord's  Work and Finish Work with respect to Area A and Area B are
Substantially  Complete,  and (ii) Landlord has tendered possession of Area B to
Tenant,  free of all  tenants  and  occupants;  provided,  however,  that Area A
Commencement  Date  and the Area B  Commencement  Date,  respectively,  shall be
deemed to occur one day  sooner  for each day of Tenant  Delay  with  respect to
Landlords'  Work or Finish Work  relating  to,  respectively,  Area A or Area B;
provided,  however,  no Tenant Delay shall cause the Area A Commencement Date to
occur before the Estimated Area A  Commencement  Date or the Area B Commencement
Date to occur before the Estimated Area B  Commencement  Date (unless Tenant has
requested  delivery of Area A (or Area B, as applicable) prior to the applicable
Estimated Commencement Date in accordance with Section 2.1.1).

      Landlord and Tenant shall, at the request of either after the beginning of
the Term, execute an acknowledgment,  in recordable form,  specifying the Area A
Commencement Date and/or the Area B Commencement  Date(s) and reciting the legal
description  of the Land and the Rentable  Floor Area of the Premises as of such
date(s).

            2.4.1  EXTENSION  TERMS.  If no Event of Default by Tenant exists at
the time of the exercise of the option and at the  commencement of any Extension
Term, Tenant shall have the option,  subject to the provisions hereof, to extend
the Initial  Term for all of the space then  included in the Premises for one or
more of three successive five-year periods (each such period,





                                       

<PAGE>

an "Extension  Term"),  exerciseable as provided below (it being understood that
Tenant  shall not have the  right to  exercise  more  than one such  option at a
time). Annual Fixed Rent per square foot of Rentable Floor Area during each such
Extension  Term shall be "Fair  Market Net Rent," which shall be the annual fair
market net rent per square foot for comparable  premises in first class suburban
office and research and development  buildings in the Interstate 495 area in the
condition of the Building as of the  commencement  of such Extension Term (or in
such better condition in which the Premises are required to be maintained) for a
similar term commencing on the  commencement  date for such Extension Term under
the terms of this Lease (excluding from such calculation finish work allowances,
rent  abatements  and  the  like).  Rent  for  any  Extension  Term  shall  also
incorporate  such  additional  financial  terms in the  nature  of rent and rent
adjustments  as are  customarily  then being  included in leases for first class
suburban  office and research  space in such  buildings.  Such payments shall be
made in  accordance  with the  procedures  set forth in Article II of the Lease.
Except as otherwise  set forth  herein,  all terms and  conditions  of the Lease
shall apply during such Extension Term.

      The  option to extend  the Lease  for the first  Extension  Term  shall be
exercised and Fair Market Net Rent shall be determined as follows:

      (a) Tenant  shall,  on or before the date one year before the Initial Term
Expiration Date, time being of the essence, give Landlord notice of its exercise
of the first extension option.

      (b) If Tenant has given the notice described in subparagraph (a), Landlord
shall give Tenant notice of its proposed Fair Market Net Rent and description of
any additional financial terms (the "Rent Notice") at any time within sixty days
of the date of Tenant's notice.

      (c) Within 30 days of receipt of  Landlord's  Rent  Notice,  Tenant  shall
notify  Landlord  of Tenant's  agreement  to or  disagreement  with the terms of
Landlord's  Rent  Notice.  If Tenant  shall fail to give  Landlord the notice of
exercise  under  subparagraph  (a) or if Tenant  shall fail timely to respond to
Landlord's Rent Notice given under  subparagraph (b), time being of the essence,
Tenant's option to extend the Term shall expire and be of no further effect.  At
Tenant's request,  contained in its reply to Landlord's Rent Notice, the parties
shall negotiate in good faith with respect to Fair Market Net Rent and any other
financial terms. If Tenant and Landlord,  having negotiated in good faith, shall
agree on Fair Market Net Rent and all  additional  financial  terms on or before
the date thirty days after the date of Landlord's Rent Notice,  this Lease shall
be extended in accordance  with such  agreement.  If Landlord and Tenant fail to
agree on the Fair  Market Net Rent  within 30 days after the date of  Landlord's
Rent Notice,  Tenant shall have the right to terminate its exercise of the first
extension option by notice to Landlord before the end of such 30-day period.  If
the parties shall not have agreed by such date, (unless Tenant has, by notice to
Landlord  within such time,  terminated its exercise of such extension  option),
Fair  Market  Net  Rent  shall  be  determined  by  appraisal  as  described  in
subparagraph (d).

      (d) In the absence of agreement,  Landlord shall, within 60 days after the
date of  Landlord's  Rent  Notice,  give notice to Tenant of an  appraiser  whom
Landlord designates to ascertain Fair Market Net Rent. If within 10 days of such
notice Tenant objects to such person,  then Tenant shall give notice to Landlord
and designate another appraiser (and failure so to





                                       

<PAGE>

notify Landlord shall bind Tenant to the appraiser  designated by Landlord).  If
within 10 days of such notice Landlord objects to such person (and failure so to
notify Tenant shall bind Landlord to the appraiser  designated by Tenant),  then
both such appraisers shall meet and within 10 days of such objection designate a
third  appraiser,  who  alone  shall  within  60 days of his or her  designation
ascertain such Fair Market Net Rent.  (If the two  appraisers  fail to designate
the third  appraiser  within such time, then either Landlord or Tenant may apply
to the Boston  office of the  American  Arbitration  Association,  or,  upon the
failure or refusal of the American Arbitration to act, to the then Chief Justice
of  the  Superior  Court  Department  of  the  Massachusetts   Trial  Court  for
appointment of the third appraiser.) Any appraiser  designated shall have had at
least 10 years experience in ownership, management, leasing and/or appraising of
major  suburban  office and  research  facilities  similar in  character  to the
Building  and  shall  be  a  member  of  M.A.I.  or  A.S.R.E.C.   (or  successor
professional  organizations)  and  otherwise  qualify as an expert  witness over
objection  to give opinion  testimony  addressed to the issue of Fair Market Net
Rent in such  facilities  in a court  of  competent  jurisdiction.  The  written
opinion of Fair Market Net Rent of the  appraiser so chosen  shall  conclusively
establish such Fair Market Net Rent.  Both parties shall have the opportunity to
present  evidence in accordance  with  reasonable  procedures  prescribed by the
appraiser.  The fee of the  appraiser  shall  be paid  equally  by the  parties,
provided  that each party shall pay the fees of its own  counsel and  witnesses.
Fair  Market Net Rent may or may not, in the  discretion  of the  appraiser,  be
determined  with  reference  to CPI or other  increases,  all as such  appraiser
decides is customary at the time. If Landlord should fail or delay in giving the
notice which begins the  appraisal  procedures of this  subparagraph,  then such
procedures  shall  nevertheless  remain in effect and be applicable  when and as
invoked by Landlord  with  respect to Annual  Fixed Rent payable with respect to
any  extension  term or  expansion  space,  as the case may be;  but until  such
procedures are completed Tenant shall pay on account of Annual Fixed Rent at the
rate per square foot of Rentable  Floor Area  established  for Annual Fixed Rent
for the year prior to the  beginning of the  Extension  Term in question (or, in
the case of expansion space, for the Premises  originally  subject to the Lease)
and a retroactive  adjustment shall be made effective as of the beginning of the
Extension  Term (or term, in the case of expansion  space) when the  appraiser's
decision is rendered.  Any  overpayments  by Tenant  hereunder shall be credited
against the next payments of rent due  hereunder.  Any  underpayments  by Tenant
shall be due and payable within thirty (30) days after the appraiser's  decision
is rendered.

      The option to extend the Lease for the  second and third  Extension  Terms
shall be exercised and Fair Market Net Rent shall be determined as follows:

      (e) Tenant shall,  on or before the date one year before the expiration of
the first Extension Term (or second  Extension Term, as applicable),  time being
of the essence, give Landlord notice of its exercise of the second (or third, as
applicable) extension option.

      (f) If Tenant has given the notice described in subparagraph (e), Landlord
shall give Tenant notice of its proposed Fair Market Net Rent and description of
any additional financial terms (the "Rent Notice") at any time within sixty days
of the date of Tenant's notice.

      (g) Within 30 days of receipt of Landlord's Rent Notice, Tenant shall
notify Landlord of Tenant's agreement to or disagreement with the terms of
Landlord's Rent Notice. At Tenant's






                                       

<PAGE>


request,  contained in its reply to  Landlord's  Rent Notice,  the parties shall
negotiate  in good  faith  with  respect  to Fair  Market Net Rent and any other
financial  terms.  If Tenant shall fail to give  Landlord the notice of exercise
under  subparagraph  (e) or if Tenant shall fail timely to respond to Landlord's
Rent Notice given under  subparagraph  (f), time being of the essence,  Tenant's
second or third (as the case may be) option to extend the Term shall  expire and
be of no further  effect.  If Tenant and  Landlord,  having  negotiated  in good
faith, shall agree on Fair Market Net Rent and all additional financial terms on
or before the date thirty  days after the date of the  Landlord's  Rent  Notice,
this Lease shall be extended in accordance with such agreement.  If Landlord and
Tenant  fail to agree on the Fair  Market Net Rent within 30 days after the date
of Landlord's Rent Notice, Tenant shall have the right to terminate its exercise
of the first  extension  option by notice  to  Landlord  before  the end of such
30-day  period.  If the parties  shall not have agreed by such date,  and unless
Tenant has by notice to Landlord  within such time,  terminated  its exercise of
such extension option,  Fair Market Net Rent shall be determined by appraisal as
described in subparagraph  (d). Any  overpayments  by Tenant  hereunder shall be
credited against the next payments of rent due hereunder.  Any  underpayments by
Tenant shall be due and payable  within  thirty (30) days after the  appraiser's
decision is rendered.

      2.5   ANNUAL FIXED RENT
            -----------------

      Commencing as of the Rent  Commencement  Date, Tenant covenants and agrees
to pay rent at an  annual  rate  equal to the  Annual  Fixed  Rent set  forth in
Section  1.1  in  effect  from  time  to  time  to  Landlord  in  equal  monthly
installments (as adjusted from time to time) in advance on the first day of each
calendar month during the Term. Annual Fixed Rent shall be based on the Rentable
Floor Area of the Premises from time to time.  All payments shall be due without
billing  or demand  and  without  deduction,  set off or  counterclaim.  For the
purposes of this Lease,  the first  "Lease Year" shall mean the period of twelve
full calendar  months after the Rent  Commencement  Date, and subsequent  "Lease
Years" shall mean the  subsequent  consecutive  periods of twelve full  calendar
months in the Term.  If the Rent  Commencement  Date occurs on a date other than
the  first  day of a  calendar  month,  or if the Term  includes  at its end any
partial Lease Year, the Annual Fixed Rent payable for any partial calendar month
immediately  after the Rent Commencement Date or for any such partial Lease Year
shall be equal to the annual amount of Annual Fixed Rent then in effect prorated
according to the fraction of the number of days in a full Lease Year within such
partial calendar month after the Rent  Commencement  Date or within such partial
Lease Year,  as the case may be. Any prorated  payment for the partial  calendar
month  after the Rent  Commencement  Date shall be due on the Rent  Commencement
Date. If the Term expires on a day other than the last day of a calendar  month,
the monthly  installment  of Annual Fixed Rent for the  calendar  month in which
such Term expires shall be prorated on a daily basis  according to the number of
days in such  calendar  month within the Term.  If the rate of Annual Fixed Rent
changes during any Lease Year due to the delivery of portions of the Premises to
Tenant  in  accordance  with  Section  2.1.1 of this  Lease or due to any  other
provision of this Lease, the total Annual Fixed Rent payable for such Lease Year
shall be equal to the sum of (i) the annual rate of Annual  Fixed Rent in effect
at the  beginning of such Lease Year  prorated  according to the fraction of the
number of days in such Lease Year during which such rate is in effect,  and (ii)
the annual rate of Annual Fixed Rent in effect  after each such change  prorated
according to the respective fractions of the number of days in such Lease Year




                                       

<PAGE>


during which each such  changed  rate of Annual Fixed Rent is in effect.  If any
such  change in the rate of Annual  Fixed  Rent  occurs on a date other than the
first day of a calendar month, the monthly  installment of Annual Fixed Rent for
the  month  in which  such  change  occurs  shall be equal to the sum of (x) the
monthly  installment  of Annual Fixed Rent  applicable  at the beginning of such
month prorated  according to the fraction of the number of days in such calendar
month during which such initial monthly  installment is applicable,  and (y) the
monthly  installment  of Annual  Fixed Rent  applicable  after each such  change
prorated  according  to the  respective  fractions of the number of days in such
calendar month during which each such changed  installment  is  applicable.  All
payments shall be payable to landlord at Landlord's  Original  Address,  both as
specified  in Section  1.1, or to such other  entities  at such other  places as
Landlord may from time to time designate by written notice to Tenant.

      2.6   ADDITIONAL RENT - TAXES AND OPERATING EXPENSES
            ----------------------------------------------

            2.6.1 ADDITIONAL RENT - GENERAL COVENANT.  Commencing as of the Rent
Commencement  Date, Tenant covenants and agrees to pay to Landlord in accordance
with Section  2.6.2 hereof,  as additional  rent, an amount with respect to each
calendar year equal to the product of (a) Tenant's  Proportionate Share (defined
below) and (b) the total of Landlord's  Operating  Expenses for such Lease Year.
"Tenant's  Proportionate  Share" for all of Landlord's  Operating Expenses other
than those  relating to the  Additional  Land and the Exclusive  Parking  Spaces
shall mean the following fractions:  (x) from the Rent Commencement Date through
the Area A Commencement  Date, the Rentable Floor Area of the Premises from time
to time divided by the Rentable Floor Area of the Building (it being  understood
that if Tenant  temporarily  occupies  all or any  portion of Area B pursuant to
Section  2.4 for the  conduct  of its  business  (and  not for the  purposes  of
preparing Area B for Tenant's use and occupancy) such portion of Area B shall be
included in the Premises for the purposes of this Section  2.6.1);  and (y) from
the Area A Commencement  Date through the  expiration or earlier  termination of
the Term,  258,851  square feet  divided by the sum of 258,851 and the  rentable
floor  area of  those  portions  of Area C  occupied  by any  tenant;  provided,
however,  if Tenant exercises its right of first refusal with respect to Area C,
after  the  commencement  of the  term of  Tenant's  lease  of Area C,  Tenant's
Proportionate Share shall equal 100%. "Tenant's  Proportionate Share" for all of
Landlord's  Operating Expenses relating to the Additional Land and the Exclusive
Parking  Spaces  shall be (A) 0% until  the later of (i) the  completion  of the
Exclusive  Parking  Spaces  under  Article  XII of this  Lease  or (ii) the Rent
Commencement  Date and (B) 100% thereafter,  for the balance of the Term. If the
Rent  Commencement  Date occurs on a date other than the first day of a calendar
year, or if the Term ends on a date other than the last day of a calendar  year,
the additional rent payable under this Section 2.6 for any partial calendar year
immediately after the Rent Commencement Date or before the end of the Term shall
be equal to the annual  amount of  Tenant's  Proportionate  Share of  Landlord's
Operation  Expenses  then in effect  prorated on a daily basis  according to the
fraction of a full calendar year after the Rent  Commencement Date or before the
end of the Term,  as the case may be. If Tenant's  Proportionate  Share  changes
during any  calendar  year due to the  delivery of  portions of the  Premises to
Tenant in  accordance  with  Section  2.1.1 of this Lease or due to this Section
2.6.1,  the total  additional rent payable under this Section 2.6 for such Lease
Year shall be equal to the sum of (i) the annual amount of Tenant's




                                       

<PAGE>


Proportionate Share of Landlord's Operating Expenses applicable at the beginning
of such calendar  year prorated on a daily basis  according to the fraction of a
full calendar year during which such amount is  applicable,  and (ii) the annual
amount of Tenant's  Proportionate  Share of Operating Expenses  applicable after
each such change prorated on a daily basis according to the respective fractions
of  a  full  calendar  year  during  which  each  changed   amount  of  Tenant's
Proportionate Share of Landlord's Operating Expenses is applicable.

            2.6.2  PAYMENT.  On or  prior  to the  Term  Commencement  Date  and
thereafter  on or prior to the Rent  Commencement  Date,  and on or prior to the
beginning of each subsequent  calendar year,  Landlord shall provide Tenant with
Landlord's  reasonable  written estimate of the Operating  Expenses for the next
period or calendar year.  Additional  rent for Tenant's  Proportionate  Share of
Landlord's  Operating  Expenses  under  this  Section  2.6 shall be paid for any
portion of a month commencing as of the Rent Commencement Date and thereafter in
monthly  installments  on the  first  day of  each  calendar  month  in  amounts
reasonably  estimated by Landlord for the then current  period or calendar  year
(it being understood that as of the Rent  Commencement Date and at the beginning
of each subsequent calendar year, such installments shall be in amounts equal to
one-twelfth of Tenant's  Proportionate Share of the then-current estimate of the
Operating  Expenses for the next calendar year).  Landlord may from time to time
and, no less  frequently  than  semi-annually,  either increase or decrease such
estimates  based on better or more current  information  relating to  Landlord's
Operating Expenses, changes in Landlord's Operating Expenses due to occupancy of
previously  vacant  space,  or  other  information   affecting  the  calculation
hereunder. Any resulting increases or decreases in additional rent due hereunder
for the then current  calendar year shall be paid in equal monthly  installments
over the balance of the  then-current  calendar  year. If the Rent  Commencement
Date  occurs on a date other than the first day of a calendar  month,  or if the
Term expires on a day other than the last day of a calendar  month,  the monthly
installment  of additional  rent for Operating  Expenses for such calendar month
shall be  prorated  on a daily  basis  according  to the  number of days in such
calendar month after the Rent  Commencement  Date or before the end of the Term,
as the case may be. If Tenant's  Proportionate Share changes during any calendar
month due to the  delivery of portions of the  Premises to Tenant in  accordance
with  Section  2.1.1 of this Lease or due to this  Section  2.6.1,  the  monthly
installment of Tenant's Proportionate Share of Landlord's Operating Expenses for
such calendar month shall be equal to the sum of (x) the monthly  installment of
Tenant's  Proportionate Share of Landlord's Operating Expenses applicable at the
beginning of such month prorated  according to the fraction of the full calendar
month during which such initial monthly  installment is applicable,  and (y) the
monthly  installment  of Tenant's  Proportionate  Share of Landlord's  Operating
Expenses  applicable after each such change prorated according to the respective
fractions of the full calendar month during which each such changed  installment
is  applicable.  Upon  issuance  thereof,  there  shall be  adjustments  between
Landlord and Tenant for the calendar year covered by such  accounting to the end
that Landlord shall have received the exact amount of additional  rent due under
this Section 2.6. Any overpayments by Tenant hereunder shall be credited against
the next  payments  of rent due under  this  Section  2.6,  subject  to the last
sentence of this Section  2.6.2.  Any  underpayments  by Tenant shall be due and
payable within thirty (30) days after Tenant's receipt of such accounting.  With
respect to the calendar year in which the Term ends,  the  adjustments  shall be
pro rated for the portion of the year included in the Term, but shall take place




                                      


<PAGE>


nevertheless at the times provided in the preceding sentences (which obligations
shall survive the  expiration  or earlier  termination  of this Lease);  and any
overpayments  by  Tenant  in such  year  shall  be  refunded  at the time of the
delivery of such accounting to Tenant, provided there are no outstanding amounts
due Landlord under this Lease at such time.

            2.6.3  LANDLORD'S  OPERATING  EXPENSES"  -  DEFINITION.  "Landlord's
Operating  Expenses"  means  all  reasonable  costs of  Landlord  in  operating,
managing,  maintaining,  and repairing the Building,  Land,  Additional Land and
Exclusive  Parking Spaces and (subject to the terms of the following  paragraph)
making  replacements  thereon,  and  providing  services to tenants,  including,
without  limitation,  the costs of the  following:  (i) supplies,  materials and
equipment  customarily  purchased or rented and total wage and salary costs paid
to and on  account  of  all  persons  engaged  in  the  operating,  maintenance,
security,  cleaning  and  repair  of the  Building  and Land,  including  Social
Security, old age and unemployment taxes, hospitalization,  disability insurance
or benefits and other  customary  so-called  "fringe  benefits";  (ii)  building
services furnished to Tenant at Landlord's cost (including the types of services
provided  to Tenant  pursuant to Section  4.1  hereof)  and  maintenance  of and
services  provided  to or on  behalf of the  Building  performed  by  Landlord's
employees  or by other  persons  under  contract  with  Landlord  or  Landlord's
Managing Agent or building  service agent  ("Building  Service  Agents");  (iii)
utilities consumed and expenses incurred in the operation and maintenance of the
Building  (both  common  areas and  tenant  areas) and Land  including,  without
limitation,  oil, gas,  electricity (the foregoing shall not include electricity
provided for other  tenants in their  premises)  water and sewer (but  excluding
water and sewer  charges  reimbursed to Landlord by other tenants or Tenant) and
snow  removal;  (iv)  insurance;  (v) costs in the  nature  of  common  area and
facilities  costs of the  development  owned by Landlord and which  includes the
land and the Buildings (to the extent such development  includes land other than
the  Land)  reasonably  allocated  to the Land and  Building  including  without
limitation,  road and grounds  maintenance,  snow  plowing and removal and other
costs of  operating,  maintaining,  repairing  and  servicing  common  areas and
facilities;  (vi) an allowance for building service fees and management fees, in
an aggregate amount equal to $0.30 per square foot of Rentable Floor Area of the
Building  for the Initial  Term (it being  understood  that such  allowance  may
increase during any Extension Term);  (vii) "Landlord's  Taxes" as defined below
and (viii) costs incurred by Landlord in connection  with the  requirements  set
forth in that certain letter dated October 10, 1996 from Robert A. Kimball, P.E.
to Rizzo Associates, Inc. (the "DEP Letter"), it being understood that any costs
in the nature of capital  expenses  shall be  amortized in  accordance  with the
terms of the  following  paragraph.  If  Landlord  is not  obligated  to furnish
cleaning  and  janitorial  services,  or any other item,  the costs of which are
included in Landlord's Operating Expenses, to all rentable areas of the Building
(any such item not  furnished  to all such  rentable  areas is  referred to as a
"restricted item"), Additional Rent due hereunder with respect to any restricted
item  furnished  to or  benefiting  the Premises for any period shall be (i) the
cost of such item for the period multiplied by (ii) the percentage calculated by
dividing  the  Rentable  Floor  Area of the  Premises  (as the  Premises  may be
expanded from time to time) by the total  rentable floor area of all premises so
benefited.  No amount shall be included in  Landlord's  Operating  Expenses with
respect to any restricted item not furnished to or benefiting the Premises.



                                       

<PAGE>


      If Landlord, in its reasonable  discretion,  installs a new or replacement
capital item for the purpose of reducing or conserving  the use of energy in the
Building  (provided that such reduction or conservation of energy is required by
applicable  law)  or  otherwise  relating  to  the  operation  of  the  Building
(including but not limited to the replacement of the roof, foundation,  exterior
walls,   and  other  structural   components  of  the  Building,   the  heating,
ventilating,  air  conditioning,   electrical,  plumbing,  emergency  and  other
mechanical  equipment and systems,  and the on-site  subsurface  sewage disposal
system and the Exclusive Parking Spaces (as defined in Article XII hereof)), the
cost of such  item  shall  be  amortized  over its  useful  life  determined  in
accordance with generally  accepted  accounting  principles with interest at the
so-called  prime rate from time to time published by THE WALL STREET JOURNAL (or
substitute  publication  reasonably  selected  by  Landlord  if THE WALL  STREET
JOURNAL  shall  cease  publication  of such  information  and  only  the  annual
amortized  portion  (together  with  interest)  shall be included in  Landlord's
Operating Expenses for any year.

      Notwithstanding  anything to the  contrary  herein,  Landlord's  Operating
Expenses  shall not include any of the following  costs or expenses  incurred by
Landlord:  (i)  salaries,  wages,  benefits  and other  expenses of  executives,
principals, and off-site or central office, accounting, and administrative staff
of Landlord or Landlord's  Management Agent (except as the same may be reflected
in the  management  fee for the  Building  or  attributable  to actual  Building
operations);   (ii)  payments  of  principal,   interest  or  other  charges  on
indebtedness  secured by a mortgage  or other  security  interest  covering  any
portion of the  Building or the Land;  (iii)  rent,  additional  rent,  or other
charges payable under any ground lease or superior lease affecting the Land, the
Building,  or the  parking  areas  described  in  Article  XII  hereof (it being
understood  that the  foregoing  shall not be  construed to include any costs of
Landlord in operating,  managing,  maintaining, and repairing such parking areas
or making replacements  thereon);  (iv) costs of leasehold  improvements made in
connection  with the preparation of any portion of the Building for occupancy by
a new or existing tenant which is not beneficial to all tenants of the Building;
(v) costs of any  expansion of the rentable  area of the Building or the parking
areas  serving  the  Building;   (vi)  costs,  expenses  or  charges  (including
utilities) properly chargeable or attributable to a particular tenant or tenants
other than Tenant; (vii) efforts to lease portions of the building or to procure
new  tenants  for  the  Building,   including  advertising   expenses,   leasing
commissions and attorney's fees; (viii) negotiations or disputes with any tenant
of the Building other than Tenant;  (ix) Landlord's  general overhead (except as
the same may be reflected in the management fee for the Building or attributable
to actual Building operations);  (x) depreciation of the Building;  (xi) repairs
and  replacements  arising  out of a casualty  or  condemnation  (in excess of a
reasonable deductible under insurance carried by Landlord);  (xii) Landlord's or
Landlord's  Managing  Agent's  breach or  violation  of a law,  lease,  or other
obligation,  including fines, penalties and attorneys' fees; (xiii) compensation
paid to employees or other persons in  connection  with  commercial  concessions
operated by Landlord  or  Landlord's  Managing  Agent;  (xv) fees for  licenses,
permits or inspections  resulting  from the negligence or willful  misconduct of
Landlord,  Landlord's  Managing  Agent or any tenant of the Building  other than
Tenant;  (xvi)  compliance by Landlord with laws in effect and  applicable as of
the date hereof,  including  without  limitation the Americans with Disabilities
Act and the  regulations and standards  thereunder,  provided that costs of such
compliance with laws becoming effective and applicable after the date hereof may
be included in Landlord's Operating Expenses; (xvii) construction and




                                       

<PAGE>


development of the Building, other improvements on the Land or the parking areas
described  in  Article  XII  hereof  and the cost of  repair of  defects  in the
original  construction  of the Building or such  improvements  or parking areas;
(xix) any items to the  extent to which  Landlord  receives  reimbursement  from
insurance  proceeds or from a third party;  (xx) any utility or other service to
the  extent  used or  consumed  in  rentable  areas  leased to other  tenants or
occupants of the Building and provided that Tenant's use or  consumption of such
utility  or  service  is  separately   metered  at  the   Premises;   and  (xxi)
environmental testing,  remediation and compliance (it being understood that any
such costs  arising out of Tenant's use or  occupancy  of the Premises  shall be
paid by Tenant to  Landlord  as  additional  rent and as a direct  reimbursement
hereunder).

      "Landlord's  Taxes"  means all  taxes,  assessments  and  similar  charges
assessed or imposed by any  governmental  authority  upon the  Building and Land
(including  personal  property  owned by  Landlord  and  associated  therewith),
reduced by any net amounts  received as an abatement or reduction of taxes.  The
amount of special taxes or special assessments  included in Landlord's Taxes for
any year 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 paid during or with  respect to the year in question.
Landlord's  Taxes  include  expenses,  including  reasonable  fees of attorneys,
appraisers  and other  consultants,  incurred in connection  with any efforts to
obtain abatements or reduction or to assure  maintenance of Landlord's Taxes for
any year wholly or partially included in the Term, whether or not successful and
whether or not such efforts involved filing of actual abatement  applications or
initiation of formal proceedings. Landlord agrees to file abatement applications
and initiate other  appropriate  proceedings as reasonably  requested by Tenant.
Landlord's  Taxes exclude  income taxes of general  application  and all estate,
succession, inheritance and transfer taxes. If at any time during the Term there
shall be assessed on Landlord in addition to or in lieu of the whole or any part
of the ad valorem tax on real or personal property,  a capital levy or other tax
on the gross rents or other measures of building  operations,  or a governmental
income,  franchise,  excise or  similar  tax,  assessment,  levy,  charge or fee
(distinct  from any such tax now in  effect  in the  jurisdiction  in which  the
Building is located,  measured by or based,  in whole or in part,  upon building
valuation,  gross rents or other measures of building  operations or benefits of
governmental  services  furnished to the  Building or Land,  then any and all of
such taxes, assessments,  levies, charges and fees, to the extent so measured or
based,  shall be  included  within the term  Landlord's  Taxes,  but only to the
extent  that the same would be payable  if the  Building  and Land were the only
property of Landlord.

            2.6.4  SUPPLEMENTAL  RENTAL PAYMENT.  Tenant shall pay Landlord,  as
additional  rent,  without offset,  deduction or demand,  three  installments of
$83,333  each  for  the  first  three  calendar  months  following  the  Area  A
Commencement  Date payable at the time  prescribed for monthly  installments  of
Annual Fixed Rent.

            2.6.5 BOOKS AND RECORDS.  Landlord  shall maintain books and records
relating to Landlord's  Operating Expenses in accordance with generally accepted
accounting  principles.  Tenant  shall  have the right,  at its sole cost,  upon
reasonable  advance notice to Landlord and during reasonable  business hours, to
have its employees,  agents,  accountants and attorneys  review,  audit and make
copies of  Landlord's  books and records  relating  to  Operating  Expenses  and
additional rent payable by Tenant under this Lease.





                                       
<PAGE>


      2.7   ELECTRICITY
            -----------

      Subject to Section 4.2,  Landlord  shall furnish to Tenant  throughout the
Term electricity for the operation of lighting fixtures,  and electrical current
for the  operation of normal office  fixtures and  equipment and Tenant's  trade
fixtures and equipment  described in Tenant's  approved Plans.  Tenant shall pay
Landlord,  as additional  rent, for the use of such  electricity.  Such payments
shall  be made in  monthly  installments  at the  time  prescribed  for  monthly
installments  of  Annual  Fixed  Rent,  and shall be in the  amount of  Tenant's
allocable share of the cost of electricity metered to premises which include the
Premises (as reasonably determined by Landlord) at the rates charged to Landlord
therefor by the applicable public utility.  Notwithstanding the foregoing, after
all or any portion of Area A has been added to the  Premises,  Tenant  shall pay
directly to the applicable  utility company all charges for electricity  metered
to the Premises. Further notwithstanding the foregoing, after all or any portion
of Area B has been  added to the  Premises,  Tenant  shall pay  directly  to the
applicable utility company all charges for electricity metered to Area B.

      If Tenant  requires  electricity  in excess of that  supplied by Landlord,
Landlord shall, upon request, cooperate with Tenant, at Tenant's expense, in the
installation of any equipment,  wiring, conduits, and the like required for such
electricity to the Premises  provided that Tenant shall  reimburse  Landlord for
all additional  costs  incurred and further  provided that Landlord shall not be
required to take any action which is inconsistent with applicable law, insurance
regulation,  or that entails excessive or unreasonable alterations or repairs to
the Building or interference with other tenants or occupants of the Building.

      2.8   ACCESS
            ------

      Tenant, its employees,  agents, contractors and invitees shall have access
at all times to the Premises and the parking areas required under Article XII of
this Lease.


                                   ARTICLE III

                                  CONSTRUCTION


      3.1   LANDLORD'S WORK AND FINISH WORK
            -------------------------------

            3.1.1  DEFINITION.  Landlord shall, at its sole expense,  diligently
perform  the work set forth on EXHIBIT A hereto,  together  with any  additional
work reasonably  inferable as being required to complete such work in compliance
with all applicable laws,  regulations,  and codes ("Landlord's Work"). Landlord
shall complete Landlord's Work at its sole expense,  except that if (i) Landlord
encounters  conditions at the Premises which were  unforeseeable  at the time of
the execution of this Lease,  and (ii) such  unforeseeable  conditions cause the
cost of Landlord's Work to exceed the Construction  Budget,  then Landlord shall
first apply any balance of the Contingency  Allowance  toward such excess costs,
and Tenant shall be responsible for paying the




                                       

<PAGE>

balance of the excess costs of Landlord's Work resulting from such unforeseeable
conditions that remains after Landlord  exhausts the Contingency  Allowance.  If
such excess cost shall be less than or equal to  $100,000.00,  Tenant  shall pay
such amount to Landlord  within thirty (30) days after receiving from Landlord a
reasonably  detailed  written  statement of such excess  costs,  together with a
certificate  of  Landlord's  architect  stating  that  Landlord's  Work has been
completed  substantially in accordance with the Plans and evidence of payment to
and waivers of lien from,  contractors performing any portion of Landlord's Work
for which reimbursement is requested.  If such excess cost shall be greater than
$100,000.00,  upon Tenant's request and at Tenant's expense,  Landlord shall use
reasonable efforts to obtain additional  financing to pay such excess costs, and
to the extent funds for such costs are  available to Landlord,  Tenant may elect
to pay to Landlord, as additional rent, the amount of such excess amortized over
the  remainder  of the Initial  Term with  interest at the rate then  charged by
Landlord's  mortgagee (it being  understood that such rate is currently 12%), in
equal monthly  installments  on the first day of each calendar month  commencing
with the first full  calendar  month  which is at least  thirty  (30) days after
delivery to Tenant of Landlord's written statement,  architect's certificate and
evidence of payment  relating to such excess costs.  Except for Landlord's  Work
described above,  any  improvements  required to put or maintain the Building in
condition for Tenant's  occupancy,  including any  modifications of the Building
structure or systems  necessitated by Tenant's  special  requirements,  shall be
deemed to constitute Finish Work.

      Landlord's  Work and all  Finish  Work  shall be done by union  labor in a
workmanlike manner in accordance with all applicable codes, laws and regulations
using new materials of good quality,  and when completed  shall then comply with
all applicable codes, laws, and regulations. Landlord shall employ in connection
with  Landlord's  Work and  Finish  Work  only  contractors  and  subcontractors
reasonably   approved  by  Tenant.   Before   employing   any   contractors   or
subcontractors,  Landlord shall pursue competitive bidding procedures reasonably
acceptable to Tenant. Notwithstanding anything to the contrary in the foregoing,
Tenant  hereby  approves  John  Moriarty  &  Associates,  Inc.  as  the  general
contractor (the "General  Contractor")  for Landlord's Work and all Finish Work.
Tenant further approves the terms and conditions of construction contracts dated
as of October 31, 1996 between Landlord and the General  Contractor with respect
to  Landlord's  Work and Area A Finish Work,  ("Landlord's  Work  Contract"  and
"Finish Work Contract," respectively).

            3.1.2  PERMITS.  Landlord  will use  diligent  efforts  to  obtain a
building permit and all other governmental permits, licenses,  approvals and the
like required in connection with  construction of Landlord's Work,  Finish Work,
and the construction of the parking required under Article XII of this Lease.


      3.2   CONSTRUCTION FOR TENANT - FINISH WORK
            -------------------------------------

      (a) Subject to the  conditions  set forth in this  Section  3.2,  Landlord
shall also perform the work set forth on the Plans (as defined below)  including
without  limitation all renovations,  replacements and alterations  specified in
the Plans and any additional  work which is reasonably  inferable from the Plans
as being required to complete the specified renovations, replacements




                                       

<PAGE>


and alterations in compliance with all applicable laws,  regulations,  and codes
(the  "Finish  Work").  Finish  Work shall not  include  Landlord's  Work or the
installation  of  Tenant's   furniture,   business  fixtures  and  equipment  or
decorations.  Landlord shall  complete  Finish Work at Landlord's  expense,  but
Tenant shall reimburse Landlord for costs of Finish Work as set forth in Section
3.2(c),  up to a maximum sum equal to the Cost  Proposals  for Area A and Area B
(as defined below) accepted by Tenant pursuant to this Section 3.2(a),  plus all
additional  costs of  Finish  Work  arising  out of  modifications  to the Plans
requested by Tenant after Tenant's acceptance of any Cost Proposal (or necessary
to make the Plans comply with all applicable laws, regulations, and codes), less
that  portion of the  Contingency  Allowance  applied  toward  such costs  under
Section 3.2(c).

      Tenant,  at  its  sole  cost,  has  provided  to  Landlord's  Finish  Work
Representative,  and Landlord has approved, complete final construction drawings
and  specifications  for all  Finish  Work in Area A,  including  architectural,
mechanical and electrical  drawings and  specifications  (the "Area A Plans"), a
schedule of which is attached  hereto as Exhibit G. Tenant  shall,  on or before
the Tenant Area B Plan Delivery Date and at its sole cost, provide to Landlord's
Finish  Work   Representative   complete   final   construction   drawings   and
specifications  for  all  Finish  Work  in  Area  B,  including   architectural,
mechanical and electrical drawings and specifications (the "Area B Plans").  The
Area A Plans and the Area B Plans  are  collectively  referred  to herein as the
"Plans."  The Plans  shall be  prepared  by Soep  Associates,  Inc.  or  another
architect  designated  by  Tenant  and  reasonably  approved  by  Landlord  (the
"Architect").  The Area B Plans  shall not be deemed to have been  submitted  by
Tenant unless and until they are in a form which is thereafter approved.  Within
ten (10) business days after receipt of the Area B Plans, Landlord shall approve
or  disapprove  such Plans (and  provide  reasons  for any  disapproval).  If in
reviewing the Plans or other preliminary  materials  delivered to Landlord under
this Section 3.2, Landlord observes matters which will involve unavailability of
materials,  unusual costs or unusual  delays,  Landlord  will so inform  Tenant.
Landlord shall not be obliged to make any  independent  investigations  of these
matters.  If any Plans are  disapproved,  they  shall be  revised  by Tenant and
resubmitted to Landlord for approval  within ten (10) business days and the same
procedure shall be repeated until Landlord fully approves such Plans. Landlord's
approval of the Plans shall not be deemed a representation  or warranty that the
Plans are  complete or that there are no  inconsistencies  between the Plans and
the shell and core construction of the Building and/or Landlord's Work.

      Landlord  shall cause the General  Contractor to submit the Plans relating
to  the  Finish  Work  for  Area  A  for   competitive   bidding  by   unionized
subcontractors  reasonably approved by Tenant.  Tenant shall have the right, but
not the  obligation,  to specify up to two unionized  subcontractors  reasonably
acceptable to Landlord to participate in such  competitive  bidding with respect
to all subcontracts.  Landlord shall cause the General Contractor to obtain from
each such  subcontractor a final bid for its component of Finish Work. If Tenant
is not  satisfied  with the bids on any  component of such Finish Work,  'Tenant
shall have the option (i) to revise the Plans,  to submit the  revised  Plans to
Landlord  for its  approval,  and to submit the  revised  Plans to any  affected
subcontractor  for a final bid, all in accordance with this Section  3.2(a),  or
(ii) to  request  that  Landlord  submit  the Plans  for a final bid by  another
subcontractor reasonably agreed upon by Tenant and Landlord. Any actual delay in
the Substantial Completion of Finish Work relating




                                       

<PAGE>


to Area A arising out of any such revisions to the Plans and  resubmissions  for
Landlords' approval or for final bids shall be a Tenant Delay.

      Within twenty days after Landlord's approval of the Plans relating to Area
A, Landlord shall cause the General  Contractor to submit to Tenant a guaranteed
maximum  price for  completing  Finish  Work shown on such  Plans,  which  shall
consist of the total of the bids from all  subcontractors  accepted during final
bidding  relating to the Finish Work for Area A (the "Final  Price for Area A").
If Tenant exercises its option in the previous paragraph to revise the Plans for
Area  A  or  to  submit  the  Plans  for  Area  A  for  bid  by  an  alternative
subcontractor,  Landlord shall cause the General  Contractor to submit the Final
Price for Area A to Tenant within such  twenty-day  period,  subject to revision
upon  receipt  of any  bids  relating  to such  revised  Plan or from  any  such
alternative  subcontractor.  The "Cost Proposal" for the Finish Work relating to
Area A shall be equal to the sum of (i) Final Price of Area A, (ii) a charge for
the General  Contractor's  general conditions which shall not exceed the amounts
set forth in the Finish  Work  Contract,  (iii) a charge  payable to the General
Contractor which shall not exceed five and one-half percent (5.5%) of the sum of
(i) and (ii),  and (iv) a charge  payable  to  Landlord  for  management  of the
construction and installation of the Finish Work relating to Area A (the "Area A
Construction  Management  Fee") which shall not exceed three percent (3%) of the
sum  of  items  (i)-(iii).  Notwithstanding  anything  to  the  contrary  in the
foregoing,  within a reasonable  period following  completion of the Finish Work
relating to Area A, Tenant shall, in its sole discretion,  determine  whether to
increase the Area A  Construction  Management  Fee to up to five percent (5%) of
the sum of items (i)-(iii) above.

      Landlord  shall cause the General  Contractor to submit the Plans relating
to  the  Finish  Work  for  Area  B  for   competitive   bidding  by   unionized
subcontractors  reasonably approved by Tenant.  Tenant shall have the right, but
not the  obligation,  to specify up to two unionized  subcontractors  reasonably
acceptable to Landlord to participate in such  competitive  bidding with respect
to all subcontracts.  Within twenty days after Landlords'  approval of the plans
for the  Finish  Work  relating  to Area B,  Landlord  shall  cause the  General
Contractor  to obtain from each such  subcontractor  a bid for its  component of
such Finish Work. If Tenant is not  satisfied  with the bids on any component of
such Finish Work,  Tenant  shall have the option to revise the plans,  to submit
the revised Plans to Landlord for its approval,  and to submit the revised Plans
to any affected  subcontractor  for a revised bid, all in  accordance  with this
Section 3.2(a).  Any actual delay in the  Substantial  Completion of Finish Work
relating  to  Area B  arising  out of  any  such  revisions  to  the  Plans  and
resubmissions for Landlord's approval for final bids shall be a Tenant Delay.

      Within twenty days after Landlord's approval of the Plans relating to Area
B, Landlord shall cause the General  Contractor to submit to Tenant a guaranteed
maximum  price for  completing  Finish  Work shown on such  Plans,  which  shall
consist of the total of the bids from all  subcontractors  accepted during final
bidding  relating to the Finish Work for Area B (the "Final  Price for Area B").
If Tenant exercises its option in the previous paragraph to revise the Plans for
Area B,  Landlord  shall cause the General  Contractor to submit the Final Price
for Area B to Tenant  within such  twenty-day  period,  subject to revision upon
receipt of any bids relating to such revised Plan.  The "Cost  Proposal" for the
Finish Work relating to Area B shall be equal to






                                       

<PAGE>

the sum of (i) Final Price of Area B, (ii) a charge for the General Contractor's
general  conditions  which  shall not exceed the amounts set forth in the Finish
Work Contract,  (iii) a charge payable to the General Contractor which shall not
exceed five and one-half  percent  (5.5%) of the sum of (i) and (ii), and (iv) a
charge payable to Landlord for management of the  construction  and installation
of the Finish Work relating to Area B (the "Area B Construction Management Fee")
which  shall  not  exceed  three  percent  (3%) of the sum of  items  (i)-(iii).
Notwithstanding  anything to the contrary in the foregoing,  within a reasonable
period following completion of the Finish Work relating to Area B, Tenant shall,
in its sole  discretion,  determine  whether to increase the Area B Construction
Management Fee to up to five percent (5%) of the sum of items (i)-(iii) above.

      Except as otherwise  permitted in this Section 3.2(a),  Tenant's Plans may
not be  modified  in any  material  respect  after the date of this  Lease  with
respect to the Area A Plans or the Tenant Area B Plan Delivery Date with respect
to the  Area B  Plans,  except  with  Landlord's  approval  which  shall  not be
unreasonably withheld or delayed.  Tenant shall be responsible for all costs and
delays  associated  with  any  modifications  to the  Plans  including,  without
limitation,  the cost of  Architect.  Landlord  shall,  upon  Tenant's  request,
provide  estimates  of costs of all Work  which  Tenant  proposes  to include in
change  orders  issued  after the initial  approval  of  Tenant's  Plans and any
estimated delay in Substantial Completion of the Finish Work resulting from such
change orders. Landlord shall not unreasonably withhold,  delay or condition its
approval  of the  Plans  or any  modifications  to the  Plans,  but it  shall be
reasonable  for  Landlord  to  disapprove  Tenant's  Plans (or any  modification
thereto) which in Landlord's  reasonable judgment (i) would materially delay the
completion of Landlord's  Work or Finish Work,  (ii) are  incompatible  with the
design,  quality,  equipment or systems of the Building,  or (iii) would require
unusual  expense to readapt the Premises to normal office and light assembly use
upon  termination  of the Term  (except to the extent  Tenant  agrees,  prior to
Landlord's  approval of the Plans,  to readapt the Premises upon  termination of
the  Term  at its own  expense).  All  payments  required  to be made by  Tenant
hereunder, whether to Landlord or third parties, shall be deemed "rent payments"
for purposes of Article VII.

      (b) If and as long as Tenant does not materially interfere in any way with
the  construction  process (by causing  disharmony,  scheduling or  coordination
difficulties,  etc.), Tenant may, with prior permission of Landlord (which shall
not be unreasonably withheld, delayed or conditioned), and at Tenant's sole risk
and expense,  enter portions of the Premises prior to the delivery of possession
of such portion to Tenant for the purpose of installing Tenant's furnishings and
fixtures  and  equipment.   The  determination  of  whether  any  such  material
interference  has occurred or is occurring  made by Landlord's  Architect in its
reasonable judgment at Landlord's request shall be conclusive.

      (c) As Finish Work progresses,  Landlord shall pay the cost of Finish Work
from the  Contingency  Allowance  specified  in  Section  1.1 (to the extent not
applied to the cost of  Landlord's  Work in  accordance  with Section 3.1) until
such time as the Contingency Allowance is exhausted.  Thereafter, Landlord shall
submit to Tenant monthly requests for payment ("Requests for Payment") as Finish
Work progresses.  Each Request for Payment shall relate to the portion of Finish
Work which has been completed during the period covered by such Request




                                       

<PAGE>

for Payment,  shall be  accompanied  by a certificate  of  Landlord's  architect
stating that such portion of Finish Work has been  completed in accordance  with
the Plans,  and shall  include  evidence of payments to and waivers of lien from
contractors  performing Finish Work covered by previous Requests for Payment (if
not previously delivered to Tenant). Tenant shall make payment on account of all
Requests for Payment  within  twenty (20) days after receipt of such Request for
Payment,  provided,  however, that Tenant shall have the right to withhold until
final  completion of Landlord's  Work and Finish Work  (including  all Punchlist
Items) an amount equal to the greater of (i) five  percent of the Cost  Proposal
accepted  by Tenant  or (ii) the cost of  completing  any  Punchlist  Items,  as
reasonably  estimated by Landlord's  architect.  Landlord shall,  promptly after
receipt of such payments,  furnish to Tenant evidence of payments to and waivers
of lien from  contractors  performing  such Finish  Work.  The full amount which
Tenant is obligated to pay under this Section 3.2, less such withheld amount set
forth in the  foregoing  sentence,  shall be paid with the  Request  for Payment
submitted by Landlord after  Substantial  Completion (as defined in Section 2.4)
of the construction of Landlord's Work and Finish Work. As Tenant makes payments
to  Landlord  for the  cost of all  Finish  Work in  excess  of the  Contingency
Allowance  (to  the  extent  not  otherwise  applied),  Landlord  shall  pay the
contractor  for all Finish Work and deliver the Premises free of all  mechanics'
and material  men's liens imposed by reason of the Finish Work.  Notwithstanding
anything  in this  Lease  to the  contrary,  Tenant  shall  not be  entitled  to
possession of the Premises if any outstanding  Requests for Payment then due and
payable (other than amounts disputed by Tenant in good faith) have not been paid
by Tenant at the time Tenant shall  otherwise be entitled to  possession  of the
Premises.

      (d) TENANT DELAYS. "Tenant Delays" are any actual delays in the
Substantial Completion of Landlord's Work and/or Finish Work to the extent
caused by action or inaction of Tenant or any of its employees, agents or
contractors, and shall include, but not be limited to:

            (i) any such delay caused by any delay in the delivery of the Area B
Plans to Landlord  beyond the Tenant Area B Plan  Delivery  Date or a failure by
Tenant to respond within the period required under Section 3.2 of this Lease, to
the extent such delays are caused by Tenant,  the Architect (in the  performance
of  its  duties  under  contract  with  Tenant  and   attributable  to  Tenant's
instructions) or Tenant's authorized representatives, agents or employees;

            (ii) any such delay caused by  modifications,  revisions and changes
to the Plans due to a change  requested  by the  Tenant or  Tenant's  authorized
representatives, agents or employees;

            (iii) any such delay caused by the delivery, installation or
completion of any work for Tenant performed by a Tenant contractor;

            (iv)  any such delay of any kind or nature caused by a material
interference by Tenant pursuant to Section 3.2(b) above); or

            (v) any such delay  resulting  from Tenant's  failure to pay for any
Finish Work within twenty (20) days of receipt by Tenant of a bill therefor.





                                       

<PAGE>


      (e) Landlord shall use diligent  efforts to  Substantially  Complete those
portions of Landlord's Work and Finish Work affecting, relating to, or necessary
for  the  use  and  occupancy  of  Area  A on or  before  the  Estimated  Area A
Commencement Date (as may be extended  pursuant to Section 2.4).  Landlord shall
use diligent efforts to Substantially Complete those portions of Landlord's Work
and Finish Work  affecting,  relating to, or necessary for the use and occupancy
of  Area B on or  before  the  Estimated  Area B  Commencement  Date  (as may be
extended pursuant to Section  2.4)."Substantial  Completion" and  "Substantially
Complete"  shall  refer to the state of any  portion  of the  Premises  when (i)
Landlord has obtained and  delivered to Tenant a certificate  of occupancy  with
respect to such portion of the Premises and (ii) Landlord's Work and Finish Work
for such portion are complete  except for  Punchlist  Items.  "Punchlist  Items"
include only (x) those items of  Landlord's  Work and/or Finish Work which while
incomplete will not materially  interfere with Tenant's use and occupancy of the
Premises and the completion of which will not materially interfere with Tenant's
use and  occupancy of the Premises and (y) matters such as balancing of heating,
ventilating and air  conditioning  systems that cannot be completed due to their
seasonal  nature.  Landlord  shall  complete the items  identified in clause (x)
above  within 30 days after the Area A  Commencement  Date,  with respect to any
such  items  relating  only to Area A,  and  within  30 days  after  the  Area B
Commencement  Date, with respect to the remainder of such items.  Landlord shall
diligently  complete  the matters  identified  under  clause (y) above  within a
reasonable time after the Area A Commencement Date or Area B Commencement  Date,
as the case may be.

      3.3   COMPLIANCE: WITH LEASE
            ----------------------

      In  exercising  its rights under Section  3.2(b) or otherwise  entering or
occupying  the  Premises  prior  to the Rent  Commencement  Date,  Tenant  shall
perform,  and shall cause its employees,  agents,  contractors,  subcontractors,
material suppliers and laborers to perform,  all Tenant's obligations under this
Lease except the  obligations to pay Annual Fixed Rent, and additional  rent and
other charges and other  obligations  the  performance of which would be clearly
incompatible  with the  installation  of  furnishings,  fixtures  and  equipment
pursuant hereto.

      3.4   WARRANTIES
            ----------

      Landlord  shall  use best  efforts  to  obtain  from the  contractors  and
subcontractors  performing Landlord's Work and Finish Work customary contractual
assurances or warranties (the  "Warranties")  that their work was performed in a
good and workmanlike manner,  using first quality materials,  in conformity with
this Lease and all  applicable  laws,  plans,  specifications  and  construction
contracts and that such work was free of defects in  workmanship  and materials.
Landlord shall use best efforts to ensure that the Warranties  shall survive for
a period  of one year from (i) the Area A  Commencement  Date  with  respect  to
Landlord's Work and Finish Work in Area A, and (ii) the Area B Commencement Date
with respect to  Landlord's  Work and Tenant's  Work in Area B.  Landlord  shall
assign the  Warranties to Tenant.  Landlord  shall also use diligent  efforts to
obtain and shall assign to Tenant,  and shall use diligent  efforts to cause all
contractors   and   subcontractors   to  obtain  and   assign  to  Tenant,   all
manufacturers'  warranties  relating to any  components or materials  comprising
part of  Landlord's  Work or Finish Work,  including a warranty for at least ten
years on the roof of the Building and warranties on the





                                       

<PAGE>


mechanical  components of the heating,  ventilating and air conditioning system.
Any  assignments  under this  Section  3.4 shall  automatically  terminate  upon
expiration or earlier  termination of this Lease and shall  thereupon  revert to
Landlord or such person as is then the owner of the Building and the Land.

                                   ARTICLE IV

                              LANDLORD'S COVENANTS

      4.1   LANDLORD'S COVENANTS
            --------------------

      Commencing as of the Area A  Commencement  Date with respect to Area A and
with the Area B Commencement Date with respect to Area B, Landlord  covenants as
follows:

            4.1.1 BUILDING SERVICES. Landlord shall furnish services, utilities,
facilities  and  supplies  set forth in this  Section  4.1.1.  Tenant may obtain
additional services,  utilities,  facilities and supplies from time to time upon
reasonable  advance request and, in either case, the cost of the same (including
related  expenses  such as costs  for meter  installation  and  maintenance)  at
reasonable  rates from time to time  established by Landlord shall  constitute a
restricted item allocable to the Premises under Section 2.6.1.  Tenant covenants
to pay, as additional  rent, any amounts billed for  restricted  items,  payable
within ten business days after receipt of such bill.

                  4.1.1.1  WATER  CHARGES.  Landlord  shall furnish hot and cold
water for the facilities and equipment  described in Tenant's approved Plans. If
Tenant  requires,  uses or consumes  water for any other  purpose,  Landlord may
either assess on Tenant  reasonable  charges for additional  water, or install a
water  meter to measure  Tenant's  consumption.  (The cost of  installation  and
maintenance  of any such meter  shall be borne by  Tenant.)  If  Tenant's  water
consumption is measured by a separate  meter,  Tenant shall pay for all water so
consumed  together with the sewer charges based on said meter charges within ten
business days after receipt of bills therefor.

                  4.1.1.2  ELEVATOR,  HEAT AND  CLEANING.  Landlord  shall:  (i)
provide  necessary  elevator  facilities at all times;  (ii) furnish heat to the
Premises during the normal heating season on a schedule reasonably  requested by
Tenant (which may be 24 hours per day,  seven days per week,  365 days per year)
pursuant to reasonable procedures  established by Landlord;  and (iii) cause the
Common  Facilities to be kept reasonably clean.  Cleaning  standards shall be in
accordance  with  standards   generally   applicable  in  quality  research  and
development buildings in the Interstate Route 495 area.

                  4.1.1.3 AIR-CONDITIONING. Landlord shall, through the Building
air-conditioning   system,   furnish   to  and   distribute   in  the   Premises
air-conditioning as normal seasonal changes may require on a schedule reasonably
requested  by Tenant  (which may be 24 hours per day,  seven days per week,  365
days per year) may reasonably be required for the  comfortable use and occupancy
of the Premises by Tenant for the Permitted Uses. If Tenant requires  additional
air-conditioning capacity in excess of that set forth in the Plans or the plans




                                       

<PAGE>


for  Landlords'   Work,  any  additional   air-conditioning   units,   chillers,
condensers, compressors, ducts, piping and other equipment will be installed and
maintained by Landlord at Tenant's sole cost and expense, but only to the extent
that the same are compatible with the Building and its mechanical systems.

                  4.1.1.4 ENERGY  CONSERVATION.  Tenant agrees to cooperate with
Landlord and to abide by all Building  regulations which Landlord may, from time
to time,  reasonably  prescribe in accordance with Section 5.3 of this Lease for
the proper  functioning  and  protection  of the  heating  and air  conditioning
systems and in order to  maximize  the effect  thereof and to conserve  heat and
air-conditioning. Notwithstanding anything to the contrary in this Section 4.1.1
or otherwise in this Lease,  Landlord may institute such policies,  programs and
measures as may be in Landlord's  judgment  necessary to comply with  applicable
codes,  rules,  regulations  or  legally  mandated  standards  regarding  energy
conservation.

            4.1.2  REPAIRS.  Except as  otherwise  provided in this  Lease,  and
except for repairs to items  referred to below  necessitated  by Tenant's act or
failure  to act (when  Tenant  has a duty so to act)  (which  shall be  Tenant's
repair  obligation  under Section 5.2),  Landlord shall maintain  (including any
necessary repairs or replacements) the roof,  exterior walls,  exterior windows,
floor slabs,  foundation and other  structural  components of the Building,  the
heating,  ventilating,  air  conditioning,   electrical,   plumbing,  sprinkler,
emergency and other  mechanical  systems,  the on-site sewage disposal system on
the Land,  the Common  Facilities  and any other common areas and  facilities in
good  condition  and working  order  consistent  with a first  class  office and
research and development  building and in compliance  with all applicable  laws.
Costs incurred hereunder shall be governed by Section 2.6.3 above.

            4.1.3 OFFICE  IDENTIFICATION.  Landlord shall provide and install at
Tenant's  expense,  if  requested,  letters or  numerals  on entry  doors to the
Premises to identify Tenant's official name and Building address.  Tenant shall,
subject to any  applicable  governmental  approvals  and  subject to  Landlord's
design  approval  (such  approval not to be  unreasonably  withheld,  delayed or
conditioned),  be entitled to a sign to be fixed to the exterior of the Building
and  additional  signs to be placed on the Land,  provided  that such  signs are
consistent  with the standards  applicable to other  comparable  developments on
Robbins Road, Westford.  Such exterior sign shall be installed and maintained by
Landlord at Tenant's expense.  As of the Area A Commencement  Date, Tenant shall
have the right to name the Building, subject to Landlord's reasonable approval.

            4.1.4 HAZARD INSURANCE.  Landlord shall maintain throughout the Term
all-risk type hazard insurance insuring the Building,  the Exclusive Parking and
all other  improvements  on the Land to their  full  replacement  value,  with a
commercially reasonable deductible.

            4.1.5  HAZARDOUS  MATERIALS.  Except as may be disclosed in a report
prepared  by Dames & Moore dated  October 2, 1996 and reports  prepared by Rizzo
Associates,  Inc.  dated  October 31, 1996 and November 8, 1996 (copies of which
has been delivered to Tenant)  Landlord  represents that, to its best knowledge,
there are no  hazardous  materials  on the Land,  Building or Premises as of the
date hereof.




                                       

<PAGE>

            4.1.6 QUIET ENJOYMENT. Landlord covenants that Tenant, on paying the
rent and performing the tenant  obligations in this Lease,  shall peacefully and
quietly have,  hold and enjoy the  Premises,  free from any claim by Landlord or
persons claiming under Landlord,  but subject to all of the terms and provisions
hereof.

      4.2   INTERRUPTION
            ------------

      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  authorized  in this Lease or for  repairing  the Premises or from
repairs by Landlord of any portion of the  Building  however the  necessity  may
occur, provided,  however, that Landlord shall give reasonable advance notice to
Tenant,  except in an  emergency,  of any such  entry or  repairs  and shall use
reasonable  efforts to avoid interference with Tenant's use and occupancy of the
Premises.  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,  Landlord shall not be liable to Tenant
therefor,  nor,  except as otherwise  provided in Section  6.1,  shall Tenant be
entitled to any abatement or reduction of rent by reason thereof,  nor shall the
Rent Commencement  Date be delayed (once  Substantial  Completion has occurred),
nor  shall the same give rise to a claim in  Tenant's  favor  that such  failure
constitutes  actual  or  constructive,  total  or  partial,  eviction  from  the
Premises.  In no event shall  Landlord be liable for  indirect or  consequential
damages.

      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 and to
restore  such  services  as soon as  reasonably  practicable.  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
interruption of Tenant's use of the Premises by reason thereof.

      4.3   INDEMNITY
            ---------

      Landlord  shall   indemnify,   hold  harmless  and  defend  (with  counsel
reasonably  approved by Tenant) Tenant from and against any claim,  loss, damage
or liability arising out of the negligence or willful  misconduct of Landlord or
its agents,  employees,  contractors  or invitees or a default by Landlord under
this lease  (which  default  continues  beyond any  applicable  notice and grace
period).



                                       

<PAGE>

                                    ARTICLE V

                               TENANT'S COVENANTS

      5.1   MAINTENANCE AND REPAIR
            ----------------------

      Except  for  damage by fire or  casualty,  reasonable  wear and tear,  and
repairs,  maintenance and replacements required of Landlord under Section 4.1.2,
Tenant shall at all times keep the Premises  clean and in as good repair,  order
and  condition  as the  same are at the  beginning  of the Term or may be put in
thereafter.  The foregoing shall include without limitation  Tenant's obligation
to clean and maintain floors and floor coverings,  to paint and repair walls and
doors,  to replace and repair ceiling  tiles,  lights and light fixtures and the
like. Repairs and replacements shall be equivalents of original work.

      5.2   USE, WASTE AND NUISANCE
            -----------------------

      Throughout the Term,  Tenant shall use the Premises for the Permitted Uses
only. Tenant shall not injure, overload,  deface or commit waste in the Premises
or any part of the Building,  nor permit the occurrence of any nuisance  therein
or the emission  therefrom  of any  objectionable  noise,  odor,  vibration,  or
lights, nor use or permit any use of the Premises which in Landlord's reasonable
judgment  involves moral turpitude,  is contrary to law or ordinance or which is
liable to  invalidate  or increase the premium for any insurance on the Building
or its contents  (Landlord hereby  representing that the use of the Premises for
the Permitted Uses in accordance herewith does not, as of the date hereof, cause
any such  invalidation  or increase) or which is liable to render  necessary any
alterations or additions in the Building, nor obstruct in any manner any portion
of the Building  (outside of the  Premises) or the Land.  If Tenant's use of the
Premises results in an increase in the premium for any insurance on the Building
or its contents,  Landlord shall notify Tenant of such increase and Tenant shall
pay same as additional  rent.  Except as otherwise  provided in Tenant's  Plans,
Tenant may not without Landlord's consent install in the Premises any fountains,
sinks or cooking equipment (other than microwave ovens) provided that Landlord's
consent will not be unreasonably withheld with respect to items designed for the
convenience of Tenant's employees which are customary for office employees,  and
further provided that Landlord  determines that special venting or other matters
are not required in connection therewith.

      Tenant  shall  not  (either  with or  without  negligence)  cause or (with
respect to matters within Tenant's  control) permit any damage to, and shall not
permit its employees,  agents,  contractors and invitees to cause any damage to,
the  Premises,  the  Building or any  component  thereof or any land  pertaining
thereto,  by the escape,  disposal or release of any  biologically or chemically
active or other hazardous  agents,  substances,  or materials.  Nor shall Tenant
allow the  storage  or use of such  substances  or  materials  in any manner not
sanctioned by law or by the highest standards prevailing in the industry for the
storage and use of such  substances or  materials,  nor allow to be brought onto
the Premises  any such  materials  or  substances  except to use in the ordinary
course of Tenant's  business,  and then (with respect to any such  substances or
materials other than ordinary  office and cleaning  supplies) only after written
notice is given to




                                       

<PAGE>


Landlord of the identity of such  substances or materials.  Without  limitation,
hazardous  substances  and  materials  shall  include  those  described  in  the
Comprehensive Environmental Response, Compensation and Liability Act of 1980, as
amended, 42 U.S.C. S9601 et seq., the Resource Conservation and Recovery Act, as
amended,  42 U.S.C. 6901 et seq., the  Massachusetts  Hazardous Waste Management
Act, as amended,  M.G.L.  Chapter 21, and the  Massachusetts  Oil and  Hazardous
Material  Release  Prevention  Act,  as amended,  M.G.L.  Chapter  21E,  and the
regulations adopted under these acts. If any lender or governmental agency shall
ever require  periodic  testing to  ascertain  whether or not there has been any
release  of  hazardous  materials,  then the  reasonable  costs of such  testing
thereof  shall be  reimbursed  by Tenant to Landlord  upon demand as  additional
rent. In addition,  Tenant shall,  from time to time upon Landlord's  reasonable
request,  execute affidavits,  representations and the like from time to time at
Landlord's request  concerning  Tenant's best knowledge and belief regarding the
presence of hazardous  materials on the  Premises.  In all events,  Tenant shall
indemnify  Landlord  in the  manner  elsewhere  provided  from  any  release  of
hazardous  materials on the Premises  occurring while Tenant is in possession if
such release was caused or permitted by Tenant, or elsewhere if caused by Tenant
or persons acting under Tenant.

      5.3   RULES AND REGULATIONS
            ---------------------

      Tenant  shall  conform  to all  reasonable  non-discriminatory  rules  and
regulations now or hereafter  promulgated by Landlord  according to this Section
5.3 for the care and use of the  Premises,  the Building and the Land.  Landlord
shall give Tenant reasonable prior notice of any such rules and regulations. All
such rules and regulations shall apply generally to all tenants of the Building.
No such  rules and  regulations  shall  conflict  with any term of this Lease or
interfere  with access by Tenant and its employees and business  invitees to the
Premises (and parking areas described in Article XII) in accordance with Section
2.8.

      5.4   SAFETY APPLIANCES
            -----------------

      Tenant shall keep the Premises  equipped  with all safety  appliances  and
permits which, as a result of Tenant's  particular  activities,  are required by
law or ordinance or any order or regulation of any public authority,  shall keep
the Premises  equipped at all times with adequate fire  extinguishers  and other
such  equipment  required  for the  Permitted  Uses and shall make all  repairs,
alterations,  replacements,  or  additions  required  as a  result  of  Tenant's
activities.  The foregoing shall not include initial installation of sprinklers,
which shall be performed by Landlord.

      5.5   INDEMNIFICATION AND INSURANCE
            -----------------------------

      Tenant shall save Landlord,  any mortgagee and any other parties having an
interest in the Premises, the Building, or the Land (other than solely by reason
of a tenancy in the Building or the Land) and reasonably  designated by Landlord
by notice to Tenant from time to time (collectively, the "Indemnitees") harmless
and  indemnified and shall defend them with counsel  reasonably  approved by the
Landlord against any claim or loss arising out of any injury,  loss or damage to
any person or property  while on or in the  Premises  (or,  with  respect to any
employees,




                                       

<PAGE>


agents,  independent  contractors or invitees,  while on the Land) if not due to
negligence or willful  misconduct of Landlord or persons acting through Landlord
or any other designated party and to any person or property anywhere  occasioned
by any failures to act (when Tenant has a duty so to act), negligence or default
in Tenant's  obligations  under this Lease by Tenant or its  employees,  agents,
independent contractors or invitees. In addition to the foregoing,  Landlord may
make all repairs and  replacements  to the Building and Premises  resulting from
acts  or  failures  to act  (when  Tenant  has a duty  so to  act)  of  Tenant's
employees,  agents,  independent  contractors or invitees  (including damage and
breakage  occurring  as a result of work  performed  by or for  Tenant  and when
Tenant's property is being moved into or out of the Building), but only in cases
of emergency or if Tenant fails to make such repairs  within any notice and cure
period  provided  under Section 7.1 of this Lease,  and Landlord may recover all
costs and  expenses  thereof (to the extent not covered by  insurance  proceeds)
from Tenant as additional rent.  Tenant shall maintain in a responsible  company
or companies approved by Landlord,  liability  insurance in form satisfactory to
Landlord,  insuring (as additional named insureds)  Landlord,  any mortgagee and
any other parties having an interest in the Premises,  the Building, or the Land
(other  than  solely by reason of a  tenancy  in the  Building  or the Land) and
reasonably  designated  by  Landlord by notice to Tenant,  and Tenant,  as their
respective  interests  may appear,  against  all claims,  demands or actions for
injury,  death,  and property damage in amounts not less than those specified in
Section 1.1 (as such amounts may, from time to time, be reasonably  increased by
Landlord).  Such  insurance  shall  provide  that  it  will  not be  subject  to
cancellation,  termination,  or  change  except  after at  least 10 days'  prior
written notice to each  additional  insured.  The policy or policies,  or a duly
executed  certificate or certificates for the same,  together with  satisfactory
evidence  of the  payment  of the  premium  thereon,  shall  be  deposited  with
Landlord,  any  mortgagee,  and any  other  parties  having an  interest  in the
Premises,  the  Building,  or the Land and required to be named as an additional
insured  from time to time under this  Section  5.5 and,  upon  renewals of such
policies,  not less  than 15 days  prior to the  expiration  of the term of such
coverage.  If Tenant  fails to comply  with any of the  foregoing  requirements,
Landlord may obtain such  insurance on behalf of Tenant and may keep the same in
effect,  and Tenant shall pay  Landlord,  as additional  rent,  the premium cost
thereof  upon  demand.  Landlord  shall give  Tenant at least two (2) days prior
notice of its intention to obtain such  insurance on behalf of Tenant,  provided
that no such  prior  notice  shall  be  required  within  10 days  prior  to the
expiration of any such coverage or after the expiration of any such coverage.

      5.6   TENANT'S PROPERTY
            -----------------

      Except for  damage  caused by the  negligence  or  willful  misconduct  of
Landlord,  its agents,  employees or contractors or other persons acting through
Landlord , all furnishings,  fixtures, equipment, effects and property of Tenant
and of all persons claiming through Tenant which from time to time may be on the
Premises or elsewhere in the Building or in transit  thereto or therefrom  shall
be at the sole risk 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,  steam 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.  The
parties  acknowledge that damage or destruction may result from acts of cleaning
personnel and employees of other contractors working in and around





                                       

<PAGE>

the building and that Tenant shall bear the risk and cost thereof, except to the
extent arising out of Landlord's gross negligence or willful misconduct.

      5.7   ENTRY FOR REPAIRS AND INSPECTIONS
            ---------------------------------

      Tenant  shall  permit  Landlord and its agents,  upon  reasonable  advance
notice  (except in an emergency) to enter and examine the Premises at reasonable
times and,  if  Landlord  shall so elect,  to make any  repairs or  replacements
Landlord may deem necessary,  to remove at Tenant's  expense,  any  alterations,
additions,  signs, curtains, blinds, shades, awnings, aerials, flagpoles, or the
like not  consented to in writing  (but only if such consent was required  under
this Lease),  to read utility  meters  installed in the Premises and to show the
Premises to prospective tenants during the eighteen months preceding  expiration
of the Term and to  prospective  purchasers  and  mortgagees  at all  reasonable
times.

      5.8   EXPENSES AND ATTORNEYS' FEES
            ----------------------------

      Tenant  shall  pay  as  additional  rent  Landlord's  expenses,  including
reasonable  attorneys'  fees,  incurred in enforcing any  obligations  of Tenant
under  this Lease with  which  Tenant has failed to comply.  Landlord  shall pay
Tenant's expenses,  including reasonable  attorneys' fees incurred by Tenant, in
enforcing any  obligations  of Landlord under this Lease with which Landlord has
failed to comply.

      5.9   ASSIGNMENT, SUBLETTING
            ----------------------

      Tenant shall have the unrestricted right to assign this Lease or to sublet
all or any portion of the  Premises  except  that  Tenant  shall not assign this
Lease,  or sublet or license the  Premises or any portion  thereof or permit the
occupancy of all or any portion of the Premises by anybody  other than Tenant or
a Tenant Affiliate (as defined  below)(all or any of the foregoing  actions are,
for  the  purposes  of  this  and  the  following  paragraph,   referred  to  as
"assignments,"  and all or any of such  assignees,  subtenants,  licensees,  and
other  parties  are  referred  to as  "assignees")  without  obtaining,  on each
occasion,  the prior  consent of  Landlord,  provided  that  Landlord  shall not
unreasonably  withhold,  delay or condition such consent,  and Landlord shall be
required to consent to such assignment if the assignee uses the Premises for the
Permitted  Uses unless  Landlord  reasonably  determines  that (i) the  proposed
assignee's use or occupancy of the Premises will materially  increase the number
of employees in the Premises or will exceed the capacity of or unduly burden the
Building's  structure  or  heating,   ventilating,   air-conditioning,   sewage,
electrical,  or other mechanical systems (and Tenant has not agreed to make such
alterations or improvements to the Building,  as its sole cost and in accordance
with Section  5.10,  as will  increase  such  capacity or relieve such burden in
Landlord's good faith judgment) or (ii) the proposed assignee's use or occupancy
will, in Landlord's  reasonable  judgment,  involve moral  turpitude.  A "Tenant
Affiliate" shall mean any person or entity controlling,  controlled by, or under
common control with Tenant,  any successor of Tenant  resulting from a merger or
consolidation  with Tenant, or a purchaser in connection with the sale of all or
substantially  all of  Tenant's  assets.  Tenant's  request  for  consent  to an
assignment to such a third party shall include a copy of the proposed instrument
of assignment, if available, or else a statement of the proposed





                                       

<PAGE>


assignment in detail satisfactory to Landlord, together with reasonably detailed
business and other information about the proposed assignee reasonably  requested
by Landlord,  including a  description  of the intended use and occupancy of the
Premises and the  approximate  number of intended  employees to be occupying the
Premises (or portion thereof,  as applicable).  Except for assignments to Tenant
Affiliates,  if the  proposed  assignment  is for the  balance  of the  Term and
relates  to the entire  Premises,  Landlord  shall have the option  (but not the
obligation)  to  terminate  the Lease  effective  upon the date of the  proposed
assignment by giving Tenant notice of such termination  within ten business days
after Landlord's receipt of Tenant's request.

      Tenant shall pay to Landlord,  as additional rent,  Landlord's  reasonable
legal  fees  and  other  expenses  incurred  in  connection  with  any  proposed
assignment requiring Landlord's consent,  including fees for review of documents
and investigations of proposed  assignees.  Notwithstanding any such assignment,
the original Tenant named herein shall remain  directly and primarily  obligated
under this Lease.

      If this Lease is (i) the subject of an  assignment,  or (ii) if the entire
Premises is otherwise  occupied by anybody  other than Tenant for the balance of
the Term,  Landlord  may,  at any time and from time to time  require  that such
assignee agree  directly with Landlord to be liable,  jointly and severally with
Tenant,  to the extent of the obligations  undertaken by or attributable to such
assignee,  for the  performance  of all  Tenant's  agreements  under  this Lease
(including  payment of rent).  Landlord may collect rent and other  charges from
the  assignee and apply the net amount  collected to the rent and other  charges
hereunder,  but no such assignment or collection shall be deemed a waiver of the
provisions of Section 5.9, or the acceptance of the assignee,  as a tenant, or a
release of Tenant from direct and primary liability for the further  performance
of  Tenant's  covenants  hereunder.  The  consent by  Landlord  to a  particular
assignment  shall not  relieve  Tenant from any  requirement  of  obtaining  the
consent of Landlord to any further assignment.

      5.10  ALTERATIONS, ADDITIONS AND HEAVY EQUIPMENT
            ------------------------------------------

      Except as provided in Section 3.2 with  respect to initial  Finish Work in
the Premises, Tenant shall not make any alterations, additions, installations or
improvements in or to the Premises,  without obtaining Landlord's prior consent,
which (i) would  cost more than  $25,000  in any  single  instance,  (ii)  would
materially  and  adversely  affect  the  Building   structure  or  the  heating,
ventilating, air conditioning,  plumbing, electrical, emergency or other systems
of the  Building,  or (iii) would be visible from the exterior of the  Building;
provided,  however,  that Landlord  shall not  unreasonably  withhold,  delay or
condition such consent.  Promptly upon completion thereof,  Tenant shall provide
Landlord with as-built plans and specifications for any alterations,  additions,
installations or improvements not requiring  Landlord's  consent and which alter
the Premises as shown on the then current plans and  specifications as furnished
to Landlord. Any plans for alterations, additions, installations or improvements
requiring  Landlord's consent and all contractors  performing such work shall be
subject to Landlord's reasonable approval.  Landlord's approval of any plans for
such alterations, additions, installations or improvements shall not be deemed a
representation  or  warranty  that such plans are  complete or that there are no
inconsistencies  between such plans and the shell and core  construction  of the
Building,  Landlord's  Work,  or the Finish Work.  Tenant will not bring into or
install in the Premises any




                                       

<PAGE>


safes, or bulky or heavy furnishings,  equipment,  or machines without the prior
approval  of  Landlord  as to  methods  and  scheduling  of  transportation  and
installation  (Landlord may prohibit installation if the weight of any such item
will exceed floor load  capacities  reasonably  determined  by  Landlord,  or if
Landlord  decides that the same will cause  vibration or noise to be transmitted
to the Building structure or to areas outside the Premises).

      5.11  SURRENDER AND LIEN FOR RENT
            ---------------------------

      At the expiration of the Term or earlier termination of this Lease, Tenant
shall  peaceably  surrender the Premises  without the requirement of any notice,
including Finish Work and all other permanent  improvements  performed by Tenant
(such work to be in conformity with the provisions  hereof) and all replacements
thereof, including carpeting, any water or electricity meters, and all fixtures,
including  but not  limited  to all work in any way  bolted or  attached  to the
Premises  (but  excluding  any of Tenant's  trade  fixtures  and  equipment  not
installed at Landlord's expense and any improvements (other than Landlords' Work
or Finish Work) not installed or  constructed  at  Landlord's  expense and which
respect to which  Landlord  has,  prior to such  installation  or  construction,
notified  Tenant  must be  removed  at the end of the Term or which  Tenant  has
notified  Landlord of Tenant's  intention to remove before the  installation  or
construction thereof (collectively, "Tenant's Removable Property")) and work not
described  above   (including   partitions).   At  such  expiration  or  earlier
termination,  the Premises and improvements  shall be in the condition which the
same  are  required  to be  under  Section  5.1.  Tenant  shall,  at the time of
termination,  remove the goods, effects and fixtures which Tenant is directed or
permitted to remove in accordance  with the  provisions of this Section,  making
any repairs to the  Premises  and other areas  necessitated  by such removal and
leaving the Premises in broom clean and tenantable condition. Should Tenant fail
to  remove  any of such  goods,  effects,  and  fixtures,  they  shall be deemed
abandoned and Landlord may have them removed  forcibly,  if  necessary,  and may
store any of Tenant's  property in a public warehouse at the risk of Tenant.  If
such items are not removed from storage within a reasonable  period,  such items
may be sold by any  customary  methods in order to pay  storage  costs and other
expenses of  Landlord.  The  expense of such  removal,  storage  and  reasonable
repairs  necessitated  by such removal shall he borne by Tenant or reimbursed by
Tenant to  Landlord,  and  Landlord  shall have no liability as a result of such
removal, storage or sale.

      5.12  PAYMENT FOR WORK PERFORMED
            --------------------------

      Tenant  shall obtain all permits or licenses  for any work  undertaken  by
Tenant in the Premises, including the installation of equipment, furnishings and
fixtures.  Tenant shall also indemnify and save the  Indemnitees  (as defined in
Section 5.5)  harmless  from all injury,  loss,  claims,  liens or damage to any
person or property  occasioned by or arising from such work.  If any  mechanic's
lien (which term shall include all similar liens  relating to the  furnishing of
labor and  materials)  is filed against the Premises or the Building or any part
thereof or against the Land which is claimed to be attributable  to Tenant,  its
agents,  employees or contractors,  Tenant shall promptly  discharge the same by
payment or filing any necessary bond, provided that Tenant shall not be required
to  discharge  any lien which is the  subject of a good  faith  dispute  between
Tenant and a third party if such lien does not jeopardize Landlord's interest in
the Building or the




                                      
<PAGE>


Premises  or  violate  the  terms of any  agreement  with any  ground  lessor or
Financing Party (as defined in Section 9.2).

      5.13  PERSONAL PROPERTY TAXES
            -----------------------

      Tenant shall pay promptly when due all taxes (and charges in lieu thereof)
imposed  upon  personal  property in the  Premises,  no matter to whom  assessed
(including  Tenant's  Removable  Property),  provided  that Tenant  shall not be
required  to pay any tax which is the  subject of a good faith  dispute  between
Tenant and a governmental agency if such dispute does not jeopardize  Landlord's
interest in the Building or the  Premises or violate the terms of any  agreement
with any Financing Party.


                                   ARTICLE VI

                               CASUALTY AND TAKING

      6.1   DAMAGE BY FIRE OR CASUALTY
            --------------------------

      If the  Premises  or any part  thereof  shall be  damaged by fire or other
insured  casualty,  then,  subject to the last  paragraph  of this  Section 6.1,
Landlord  shall proceed with  diligence,  subject to then  applicable  statutes,
building codes, zoning ordinances and regulations of any governmental authority,
and at the expense of  Landlord  (but only to the extent of  insurance  proceeds
made  available to Landlord by any mortgagee of the building) to repair or cause
to be repaired such damage,  provided,  however, in respect of such alterations,
additions and  improvements,  originally made or installed by Tenant at Tenant's
expense, as shall have been damaged by such fire or other casualty and which are
insured by insurance  policies  required to be  maintained  hereunder,  that the
repairs  to such  Tenant's  alterations,  additions  and  improvements  shall be
performed  by Landlord but at Tenant's  expense to the extent such  alterations,
additions and  improvements  were not required under this Lease to be insured by
policies  maintained by Landlord.  All repairs to and  replacements  of Tenant's
Removable  Property  shall  be  made by and at the  expense  of  Tenant.  If the
Premises  or any  part  thereof  shall  have  been  rendered  unfit  for use and
occupation  hereunder  by reason of such  damage,  the Fixed  Rent or a just and
proportionate  part  thereof,  according  to the  nature and extent to which the
Premises shall have been so rendered  unfit,  shall be abated until the Premises
(except  as to the  property  which is to be  repaired  by or at the  expense of
Tenant)  shall have been restored as nearly as  practicable  to the condition in
which  they were  immediately  prior to such fire or other  casualty,  provided,
however,  that if Landlord or any  mortgagee of the Building  shall be unable to
collect the insurance proceeds (including rent insurance proceeds) applicable to
such  damage  because  of any act or  negligence  on the part of  Tenant  or the
employees,  licensees  or invitees of Tenant,  resulting  in some  violation  of
applicable  law,  the terms of any  insurance  policy  required  to be  retained
hereunder,  or the terms of this Lease,  or because of any act or  negligence on
the part of Tenant or the employees,  licensees or invitees of Tenant, resulting
in a failure to  cooperate  with  Landlord or any  mortgagee  of the Building in
connection  with  Landlord's  efforts to make its insurance  claim,  the cost of
repairing such damage shall be paid by Tenant and there shall be no abatement





                                       
<PAGE>


of rent.  Landlord  shall not be  liable  for  delays in the  making of any such
repairs  which  are  due  to  government  regulation,  casualties  and  strikes,
unavailability of labor and materials,  delays in obtaining  insurance proceeds,
and other causes beyond the reasonable  control of Landlord,  nor shall Landlord
be liable for any inconvenience or annoyance to Tenant or injury to the business
of Tenant resulting from delays in repairing such damage.

      If (i) the Premises are so damaged by fire or other  casualty  (whether or
not insured) at any time during the last thirty months of the Term that the cost
to repair such damage is reasonably  estimated to exceed  one-third of the total
Annual Fixed Rent payable hereunder for the period from the estimated completion
date of  repair  until the end of the  Term,  or (ii) at any time  damage to the
Building  occurs by fire or other  insured  casualty and any mortgagee or ground
lessor shall refuse to permit  insurance  proceeds to be utilized for the repair
or  replacement  of such  property  and Landlord  determines  not to repair such
damage,  then and in any of such  events,  this Lease and the term hereof may be
terminated  at the  election of  Landlord  by a notice  from  Landlord to Tenant
within  sixty  (60) days,  or such  longer  period as is  required  to  complete
arrangements  with any  mortgagee or ground  lessor  regarding  such  situation,
following  such fire or other  casualty,  the effective  termination  date which
shall be not less than thirty (30) days after the day on which such  termination
notice is received by Tenant.  In the event of any  termination,  the term shall
expire as  though  such  effective  termination  date  were the date  originally
stipulated  in  Section  1.1 for the end of the  Term  and the  Fixed  Rent  and
additional rent for Operating Expenses shall be apportioned as of such date.

      In any case of  casualty,  Landlord  shall  notify  Tenant  within 90 days
whether Landlord intends to repair and whether Landlord anticipates that repairs
to the  Premises  will  exceed one year to bring to  completion.  If  Landlord's
notice  states that such  repairs are not  expected to be  completed  within one
year,  Tenant  shall be entitled to  terminate  this Lease by notice to Landlord
given within 120 days of such  casualty,  and this Lease shall then terminate as
if such date were the date of the ordinary  expiration  of the Term. If Landlord
shall not have Substantially  Completed its repair obligations  hereunder within
one year, Tenant shall be entitled to terminate this Lease by notice to Landlord
given within 13 months of such  casualty,  and this Lease shall  terminate as if
such date were the date of the ordinary expiration of the Term.

      6.2   CONDEMNATION - EMINENT DOMAIN
            -----------------------------

      In case  during the Term all of the  Premises or the  Building  are taken,
condemned,  requisitioned  or  sold  in or on  account  of  any  eminent  domain
proceeding  or by other  action by any  authority  having  the power of  eminent
domain (any of the foregoing being hereinafter referred to as a "Taking" and any
portion of the Premises or the Building  subjected to a Taking being referred to
as being "Taken") this Lease shall  terminate as of the date of the Taking as if
such date were the date of the ordinary  expiration of the Term. If at least 20%
of the Premises are Taken,  Tenant shall have the right to terminate  this Lease
(notwithstanding  that  Landlord's  entire  interest may have been  divested) by
notice given to Landlord  within 90 days after the date of such  taking.  If the
remainder of the Premises are not in a proper  condition for use and occupation,
Landlord shall, as promptly as practicable, notify Tenant of the extent to which
repairs to the Premises can be made based on available  proceeds of condemnation
("Landlord's





                                       

<PAGE>



Condemnation  Notice").  If  such a  substantial  part  of the  Building  or the
Premises are Taken that the  remainder  of the Building or the Premises  cannot,
after any repairs  proposed by Landlord,  be operated in the ordinary  course of
Tenant's or Landlord's  business,  Landlord and Tenant shall each have the right
to terminate this Lease by notice to the other within 90 days after the delivery
of Landlord's  Condemnation Notice. Any notice of termination under this Section
6.2 shall  specify  the  effective  date of  termination,  and this Lease  shall
terminate on such date as if such date were the date of the ordinary  expiration
of the Term. The effective  date of termination  specified by Landlord or Tenant
shall not be less than 15 nor more than 30 days after the date of notice of such
termination.  Unless terminated pursuant to the foregoing provisions, this Lease
shall  remain in full  force and  effect  following  any such  taking,  subject,
however,  to the  following  provisions.  If in any such case the  Premises  are
rendered unfit for use and occupation and this Lease is not terminated, Landlord
shall  use due  diligence  (following  the  expiration  of the  period  in which
Landlord or Tenant may terminate this Lease pursuant to the foregoing provisions
of this Section),  to the extent of the available  proceeds of condemnation,  to
put the  Premises,  or what may remain  thereof  (excluding  Tenant's  Removable
Property), into proper condition for use and occupation and a just proportion of
the Fixed Rent and  additional  rent for  Operating  Expenses  according  to the
nature and  extent of the  injury  shall be abated  until the  Premises  or such
remainder  shall have been put by Landlord in such  condition;  and in case of a
taking which permanently reduces the area of the Premises,  a just proportion of
the Fixed Rent and  additional  rent for Operating  Expenses shall be abated for
the remainder of the Term.

      6.3   EMINENT DOMAIN AWARD
            --------------------

      Except  for  Tenant's  relocation  expenses  and any  awards for damage to
Tenant's  Removable  Property  (specifically so designated) and except for other
awards  specifically  designated to Tenant which do not reduce Landlord's award,
Landlord  reserves  to itself  any and all  rights to  receive  awards  made for
damages to the Premises,  Building and Land 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  releases  and assigns to Landlord  all  Tenant's  rights to such
awards, and covenants to deliver such further assignments and assurances thereof
as Landlord may from time to time request.

      6.4   TEMPORARY TAKING
            ----------------

      In the  event  of any  taking  of the  Premises  or any part  thereof  for
temporary  use not  exceeding  90 days,  (i)  this  Lease  shall  be and  remain
unaffected  thereby but rent shall abate, and (ii) Landlord shall be entitled to
receive for itself such  portion or portions of any award made for such use with
respect to the period of the taking which is within the Term,  provided  that if
such taking shall remain in force at the  expiration or earlier  termination  of
this Lease, Tenant shall then pay to Landlord a sum equal to the reasonable cost
of performing Tenant's  obligations under Section 5.11 with respect to surrender
of the Premises and upon such payment shall be excused from such obligations.





                                       

<PAGE>


                                   ARTICLE VII

                                     DEFAULT


      7.1   TERMINATION FOR DEFAULT OR INSOLVENCY
            -------------------------------------

      This Lease is upon the  condition  that (1) if Tenant shall fail timely to
provide or replace  any  security  deposit  under  Article X  (including  timely
replacements  to any Letter of Credit  tendered as a security  deposit) and such
failure  shall  continue  for  twenty  (20) days  after  notice to Tenant (or if
earlier,  the date ten (10) business days prior to the  expiration of any Letter
of  Credit);  or (2) if Tenant  shall fail to perform or observe any of Tenant's
other  covenants,  and if such failure  shall  continue,  in the case of rent or
payment  of any sum due  Landlord  hereunder,  for more than five (5) days after
notice from Landlord, or in any other case, after notice from Landlord, for more
than thirty (30) days after notice from Landlord (provided that if correction of
any such non-monetary  matter reasonably requires longer than 30 days and Tenant
so notifies  Landlord  within 10 days together with an estimate of time required
for such cure, Tenant shall be allowed such longer period, but only if such cure
is begun within such 30-day  period and is thereafter  diligently  prosecuted to
completion  and such delay does not cause  increased risk of damage to person or
property);  or (3) if three or more notices under clause (2) hereof are given in
any twelve  month  period  (failure to pay rent or any other sum for more than 5
days after the  particular due date shall have the same effect under this clause
(2) as such a notice,  regardless  of  whether  or not a notice  was given  with
respect to any such failure);  (4) if Tenant shall or abandon all or any portion
of the  Premises;  or (5) if the  leasehold  hereby  created  shall  be taken on
execution,  or by other  process of law, or if any  assignment  shall be made of
Tenant's  property or the  property  of any  guarantor  of Tenant's  obligations
hereunder  ("Guarantor")  for the  benefit of  creditors;  or (6) if a receiver,
guardian,  conservator,  trustee  in  bankruptcy  or  similar  officer  shall be
appointed by a court of competent jurisdiction to take charge of all or any part
of Tenant's or the Guarantor's  property and such  appointment is not discharged
within 90 days  thereafter or if a petition  including,  without  limitation,  a
petition for  reorganization  or arrangement is filed by Tenant or the Guarantor
under any bankruptcy law or is filed against Tenant or the Guarantor and, in the
case of a filing against Tenant only, the same shall not be dismissed  within 90
days from the date upon which it is filed (each of the  foregoing (1) through 6)
being an "Event of  Default"),  then,  and in any of said cases,  Landlord  may,
immediately or at any time  thereafter,  elect to terminate this Lease by notice
to Tenant and to recover  possession of the Premises  under and by virtue of the
provisions  of the  laws of The  Commonwealth  of  Massachusetts  or such  other
proceedings,  including notice, re-entry or possession. Thereupon Landlord shall
be entitled to recover possession of the Premises from Tenant and those claiming
through or under the Tenant.  Such termination of this Lease and repossession of
the Premises  shall be without  prejudice to any remedies  which  Landlord might
otherwise  have for arrears of rent or for a prior breach of the  provisions  of
this Lease.  Landlord and Tenant agree that, at Landlord's  option,  a notice by
Landlord alleging default hereunder shall constitute a statutory notice to quit,
Tenant  hereby  waiving  any  further  notice to quit and  notice of  Landlord's
intention  to  reenter  and any grace  periods  provided  for  herein  shall run
concurrently with any statutory periods.



                                       

<PAGE>


      7.2   REIMBURSEMENT OF LANDLORD'S EXPENSES
            ------------------------------------

      In the case of termination  of this Lease pursuant to Section 7.1,  Tenant
shall  reimburse  Landlord  for  all  reasonable  expenses  arising  out of such
termination,  including  without  limitation,  all costs  incurred in collecting
amounts due from Tenant under this Lease (including  reasonable attorneys' fees,
costs of  litigation  and the  like);  all  expenses  incurred  by  Landlord  in
attempting  to relet the Premises or parts  thereof  (including  advertisements,
brokerage  commissions,  Tenant's allowances,  costs of preparing space, and the
like);  and all Landlord's  other  reasonable  expenditures  necessitated by the
termination.  The reimbursement from Tenant shall be due and payable immediately
from time to time upon notice from Landlord  that an expense has been  incurred,
without  regard  to  whether  the  expense  was  incurred  before  or after  the
termination.

      7.3   DAMAGES
            -------

      Landlord  may  elect by  written  notice  to  Tenant  within  four  months
following  such  termination  to be  indemnified  for loss of rent by a lump sum
payment  representing  the then present  value of the amount of rent which would
have been paid in accordance with this Lease for the remainder of the Term minus
the then  present  value of the  aggregate  fair  market  rent  payable  for the
Premises  for  the  remainder  of the  Term  (if  less  than  the  rent  payable
hereunder), estimated as of the date of the termination, and taking into account
reasonable  projections  of vacancy and time  required to re-lease the Premises.
(For the purposes of  calculating  the rent which would have been paid hereunder
for the lump sum  payment  calculation  described  herein,  the last full year's
additional  rent  under  Section  2.6 is to be  deemed  constant  for each  year
thereafter.  The Federal Reserve discount rate (or equivalent)  shall be used in
calculating  present  values.)  Should the  parties be unable to agree on a fair
market rent, the matter shall be submitted,  upon the demand of either party, to
the Boston, Massachusetts office of the American Arbitration Association, with a
request for  arbitration  in accordance  with the rules of the  Association by a
single  arbitrator  who  shall  be an MAI  appraiser  with at  least  ten  years
experience  as an  appraiser of suburban  commercial  real estate in the Greater
Boston  Area.  The  parties  agree that a decision  of the  arbitrator  shall be
conclusive  and binding  upon them.  If, at the end of the Term,  the rent which
Landlord has actually received from the Premises is less than the aggregate fair
market rent  estimated as  aforesaid,  Tenant shall  thereupon  pay Landlord the
amount of such  difference.  Should Landlord fail to make the election  provided
for in this Section 7.3, Tenant shall indemnify Landlord for the loss of rent by
a payment at the end of each month which  would have been  included in the Term,
representing  the  difference  between  the rent  which  would have been paid in
accordance  with this Lease (Annual Fixed Rent under Section 2.5, and additional
rent which would have been payable under Section 2.6 to be ascertained  monthly)
and the rent actually  derived from the Premises by Landlord for such month (the
amount of rent  deemed  derived  shall be the  actual  amount  less any  portion
thereof  attributable to Landlord's  reletting expenses described in Section 7.2
which have not been reimbursed by Tenant thereunder).

      In lieu of any other  damages or indemnity and in lieu of full recovery by
Landlord of all sums payable under all the foregoing  provisions of this Section
7.3, Landlord may by written

                                      

<PAGE>


notice to Tenant within 6 months after  termination  under any of the provisions
contained in Section 7.1 and before such full  recovery,  elect to recover,  and
Tenant shall  thereupon pay, as liquidated  damages under Section 7.3, an amount
equal to the lesser of (i) the aggregate of the Fixed Rent under Section 2.5 and
additional  rent under  Section  2.6 for the balance of the Term had it not been
terminated or (ii) the aggregate thereof for the 12 months ending one year after
the  termination  date,  plus in  either  case  the  amount  of  Fixed  Rent and
additional  rent of any kind accrued and unpaid at the time of  termination  and
less the amount of any recovery by Landlord  under the  foregoing  provisions of
this  Section  7.3 up to the time of payment  of such  liquidated  damages  (but
reduced-by any amounts of reimbursement  under Section 7.2).  Liquidated damages
hereunder  shall not be in lieu of any claims for  reimbursement  under  Section
7.2.

      7.4   MITIGATION
            ----------

      In the event of a termination  of this Lease under  Section 7.1,  Landlord
shall use reasonable  efforts to relet the Premises,  it being  understood  that
"reasonable  efforts"  for the  purposes of this Section 7.4 shall be limited to
placing the Premises  with a reputable  commercial  broker and  Landlord's  good
faith  exploration of reasonable  potential tenants presented by such broker, it
being  understood  that in no event  shall  Landlord  be  obligated  to rent the
Premises  prior to other  comparable  vacant space in the Building,  if any. Any
obligation imposed by this Lease or by applicable law upon Landlord to relet the
Premises shall be subject to the reasonable requirements of Landlord to lease to
high quality tenants and to develop the Building in a harmonious  manner with an
appropriate mix of uses,  tenants,  floor areas and terms of tenancies,  and the
like.

      7.5   CLAIMS IN BANKRUPTCY
            --------------------

      Nothing herein shall limit or prejudice the right of Landlord to prove and
obtain   in  a   proceeding   for   bankruptcy,   insolvency,   arrangement   or
reorganization,  by reason of the  termination,  an amount  equal to the maximum
allowed  by a statute  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 is
greater  to,  equal  to, or less  than the  amount  of the loss or damage  which
Landlord has suffered.

      7.6   LATE CHARGE
            -----------

      If any payment of Annual Fixed Rent, additional rent, or other payment due
from Tenant to Landlord is not paid when due,  then Landlord may, at its option,
without  notice and in addition to all other remedies  hereunder,  impose a late
charge on Tenant  equal to 1.5% of the amount in question for each month and for
each part thereof during which said delinquency  continues provided that no late
charge will be imposed for Annual Fixed Rent  payments  less than five days late
up to two  times  in any  calendar  year.  Such  late  charge  shall  constitute
additional rent hereunder payable upon demand.





                                       

<PAGE>



                                  ARTICLE VIII

                                  MISCELLANEOUS


      8.1   MEASUREMENT OF FLOOR AREA
            -------------------------

      The rentable floor area of the Building,  Area A, Area B, and Area C shall
be as set forth in Section 1.1. The rentable floor area of any portions  thereof
shall be as determined in good faith by Landlord's architect.

      8.2   HOLDOVER
            --------

      If Tenant remains in the Premises  after the  termination or expiration of
the Term,  such holding over shall be, except as Landlord may elect  pursuant to
the next sentence, as a tenant at will or tenant by the month (requiring 30 days
notice of  termination  by either  party to the  other) at a monthly  fixed rent
equal to one and one-half the Fixed Rent due hereunder for the last month of the
Term,  and  otherwise  subject to all the covenants  and  conditions  (including
obligations to pay additional rent under Section 2.6) of this Lease as though it
had  originally  been a  monthly  tenancy.  Notwithstanding  the  foregoing,  if
Landlord  desires  to  regain  possession  of the  Premises  promptly  after the
termination or expiration  hereof and prior to acceptance of rent for any period
thereafter,  Landlord may, at its option, forthwith re-enter and take possession
of the Premises or any part thereof  without  process or by any legal process in
force in The  Commonwealth of  Massachusetts.  Tenant shall be liable for damage
caused  wholly  or  partially  by  Tenant's  holding  over  without   Landlord's
agreement,  including  without  limitation  damages  to (or lost  rentals  from)
successor tenants and occupants of all or part of the Premises.

      8.3   ESTOPPEL CERTIFICATES
            ---------------------

      At  Landlord's  request,  from time to time,  Tenant agrees to execute and
deliver to Landlord a certificate which acknowledges the dates on which the Term
begins and ends,  tenancy and  possession of the Premises and recites such other
facts  concerning  any  provision of the Lease or payments  made under the Lease
which Landlord, a mortgagee,  or lender, or a purchaser or prospective purchaser
of the  Building or any  interest  therein or any other party may,  from time to
time,  reasonably  request.  At  Tenant's  request,  from  time to time  for any
reasonable  purpose,  Landlord  agrees  to  execute  and  deliver  to  Tenant  a
certificate of the type described in the preceding sentence. Tenant acknowledges
that the  execution  and  delivery of such  certificates  in  connection  with a
financing  or sale in a prompt  manner  constitute  requirements  of  Landlord's
financing  and/or  property  dispositions  and Tenant shall  indemnify  Landlord
against all damages (including  consequential damages in the nature of increased
costs or loss of any such  transactions and including  attorneys' fees) directly
or   indirectly   resulting   from   Tenant's   failure   to   comply   herewith
(notwithstanding  that the grace or notice period under Section 7.1 may not have
expired).




                                       

<PAGE>


      8.4   NOTICE
            ------

      Any notice,  approval and other like communication hereunder from Landlord
to Tenant or from  Tenant to  Landlord  shall be given in  writing  and shall be
deemed duly  served if and when hand  delivered  or if and when  mailed  prepaid
certified  mail  (in  either  case,  whether  or  not  accepted  for  delivery).
Communications   to  Tenant   shall  be   addressed   to   Tenant's   Authorized
Representative  at the Original Address of Tenant set forth in Section 1.1 prior
to the Term Commencement Date and thereafter at the Premises.  Communications to
Landlord  shall be addressed  to the Address of  Landlord's  Managing  Agent set
forth in  Section  1.1.  A copy of any notice to Tenant  shall be  delivered  to
Testa,  Hurwitz &  Thibeault,  125 High  Street,  Boston,  Massachusetts  02110,
Attention: Real Estate Department.  Either party may from time to time designate
other addresses within the continental United States by notice to the other.

      8.5   RIGHTS TO CURE
            --------------

      8.5.1 LANDLORD'S  RIGHT TO CURE. At any time and without notice,  Landlord
may, but need not, cure any failure by Tenant to perform its  obligations  under
this Lease which has  continued  after any  applicable  notice and grace period.
Whenever  Landlord chooses to do so, all reasonable costs and expenses  incurred
by  Landlord  in  curing  any  such  failure,  including,   without  limitation,
reasonable  attorneys'  fees  together  with interest on the amount of costs and
expenses  so incurred  at an annual  rate equal to the  so-called  prime rate of
interest  published  from time to time by The Wall Street Journal (or substitute
publication reasonably selected by Landlord if The Wall Street Journal ceases to
publish such  information) plus two percentage points shall be paid by Tenant to
Landlord on demand and shall be recoverable as additional rent.

      8.5.2  TENANT'S RIGHT TO CURE. If Landlord fails to perform any obligation
under this Lease which  obligation  is material to Tenant's use and enjoyment of
the  Premises  and such failure  continues  for more than 30 days after  written
notice from Tenant  (provided  that, if  correction  of such failure  reasonably
requires a period longer than 30 days, and if Landlord commences such correction
within 30 days and prosecutes  such  correction to completion with diligence and
continuity,  Landlord  shall be allowed such longer  period as may be reasonably
necessary  to complete  such  correction),  Tenant may,  upon 10 business  days'
notice  to  Landlord  of its  intention  so to do (such  notice to  include  the
notation "NOTICE OF INTENT TO CURE" in capital letters  prominently  displayed),
but shall not be obligated to, cure any such failure,  and all reasonable  costs
and  expenses  incurred  by Tenant in curing  such  failure  (including  without
limitation reasonable attorney's fees and interest on such costs and expenses at
an annual rate equal to the so-called prime rate of interest published from time
to time  by THE  WALL  STREET  JOURNAL  (or  substitute  publication  reasonably
selected  by  Landlord  if THE  WALL  STREET  JOURNAL  ceases  to  publish  such
information)  plus two  percentage  points)  shall be  reimbursed by Landlord to
Tenant within ten days after  Landlord  receives a written bill from the Tenant.
If Landlord fails to reimburse  Tenant for any such costs and expenses within 30
days after Landlord  receives a written demand  therefor,  Tenant shall have the
right to apply such amounts as a credit  against  payments of Annual Fixed Rent,
additional rent and other charges due from Tenant to Landlord under this Lease.





                                       

<PAGE>


      8.6   SUCCESSORS AND ASSIGNS
            ----------------------

      This Lease and the covenants and conditions  herein  contained shall inure
to the benefit of and be binding upon Landlord,  its successors and assigns, and
shall be binding upon Tenant, its successors and assigns, and shall inure to the
benefit of Tenant and only such assignees of Tenant as are permitted  hereunder.
The term "Landlord" means the original Landlord named herein, its successors and
assigns.  The term  "Tenant"  means the  original  Tenant  named  herein and its
permitted successors and assigns.

      8.7   BROKERAGE
            ---------

      Landlord agrees that it shall pay any charge which is determined to be due
Boston Real Estate Partners and Fallon Hines & O'Connor, Inc. in connection with
this Lease. The foregoing agreement is between Landlord and Tenant and shall not
be deemed to be for the benefit of such  brokers or any third  parties and shall
not be construed as an  acknowledgment  that any commission is owed to any party
by either Landlord or Tenant in connection with this Lease.  Landlord and Tenant
each  represent and warrant to the other that it has engaged in no conduct which
may or will  render  the other  liable for a  broker's  commission  or charge in
connection  with this Lease to any broker other than Boston Real Estate Partners
and Fallon  Hines &  O'Connor,  Inc.,  and  Landlord  and  Tenant  each agree to
indemnify  the  other  and hold  the  other  harmless  from  any  breach  of its
respective representation and warranty.

      8.8   WAIVER
            ------

      The failure of Landlord or of Tenant to seek redress for  violation of, or
to insist upon strict  performance  of, any covenant or condition of this Lease,
or, with respect to such failure of Landlord,  any of the rules and  regulations
referred to in Section 5.3, whether heretofore or hereafter adopted by Landlord,
shall not be deemed a waiver of such  violation  nor prevent a  subsequent  act,
which would have originally constituted a violation,  from having all the effect
of an  original  violation,  nor shall the failure of Landlord to enforce any of
said rules and regulations  against any other tenant of the Building be deemed a
waiver of any such rules or  regulations.  The receipt by Landlord of Fixed Rent
or  additional  rent with  knowledge of the breach of any covenant of this Lease
shall not be deemed  waiver of such breach.  No provision of this Lease shall be
deemed to have been waived by Landlord,  or by Tenant,  unless such waiver be in
writing  signed by the party to be  charged.  No consent  or waiver,  express or
implied,  by  Landlord  or Tenant to or of any breach of any  agreement  or duty
shall be  construed as a waiver or consent to or of any other breach of the same
or any other agreement or duty.

      8.9   ACCORD AND SATISFACTION
            -----------------------

      No  acceptance  by  Landlord  of a  lesser  sum than  the  Fixed  Rent and
additional  rent then due shall be deemed  to be other  than on  account  of the
earliest installment of such rent due, nor shall any endorsement or statement on
any check or any letter  accompanying  any check or payment as rent be deemed an
accord and  satisfaction,  and Landlord may accept such check or payment without
prejudice to Landlord's right to recover the balance of such installment or





                                       

<PAGE>


pursue any other  remedy  provided  in this Lease.  The  delivery of keys to any
employee of Landlord or to  Landlord's  Managing  Agent or any employee  thereof
shall not operate as a termination of this Lease or a surrender of the Premises.

      8.10  REMEDIES CUMULATIVE
            -------------------

      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
to which it may be lawfully  entitled in case of any breach or threatened breach
by Tenant of any  provisions  of this Lease.  In addition to the other  remedies
provided  in  this  Lease,  Landlord  shall  be  entitled  to the  restraint  by
injunction of the  violation or attempted or threatened  violation of any of the
covenants  or  conditions  of this  Lease  or to a  decree  compelling  specific
performance of any such covenants or conditions.

      8.11  PARTIAL INVALIDITY
            ------------------

      If any term 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 to persons or  circumstances  other
than  those as to which it is invalid or  unenforceable,  shall not be  affected
thereby,  and each  term of this  Lease  shall be valid and  enforceable  to the
fullest extent permitted by law.

      8.12  WAIVERS OF SUBROGATION
            ----------------------

      Any insurance  carried by either party with respect to the  Building,  the
Exclusive Parking, the Premises or property therein or occurrences thereon shall
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
hereunder 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,
whether  or not  caused by  negligence,  to the  extent  of the  indemnification
received thereunder.

      8.13  ENTIRE AGREEMENT
            ----------------

      This Lease contains all of the agreements between Landlord and Tenant with
respect to the Premises and supersedes  all prior writings and dealings  between
them with respect thereto.

      8.14  NO AGREEMENT UNTIL SIGNED
            -------------------------

      The submission of this Lease or a summary of some or all of its provisions
for examination  does not constitute a reservation of or option for the Premises
or an offer to lease and no legal  obligations  shall arise with  respect to the
Premises or other  matters  herein until this Lease is executed and delivered by
Landlord and Tenant.



                                       


<PAGE>

      8.15  TENANT'S AUTHORIZED REPRESENTATIVE
            ----------------------------------

Tenant  designates  the person  named from time to time as  Tenant's  Authorized
Representative  to take all acts of Tenant  hereunder.  Landlord may rely on the
acts of such  Authorized  Representative  without further inquiry or evidence of
authority.  Tenant's Authorized Representative shall be the person so designated
in Section 1.1 and such successors as may be named from time to time by the then
current Tenant's Authorized Representative or by Tenant's president.

      8.16  NOTICE OF LEASE
            ---------------

      Landlord  and Tenant  agree not to record this Lease.  Both  parties  will
execute,  acknowledge  and  deliver a notice of lease and if  appropriate,  both
parties  will,  at the request of either,  execute,  acknowledge  and delivery a
notice of termination of the Term,  each in recordable  form. Such notices shall
contain  only the  information  required  by law for  recording.  Tenant  hereby
irrevocably  appoints Landlord as Tenant's  attorney-in-fact  (which appointment
shall  survive  termination  of the Term)  with full  power of  substitution  to
execute,  acknowledge  and deliver a notice of  termination of lease in Tenant's
name if Tenant fails to do so within 10 business days after request therefor.

      8.17  TENANT AS BUSINESS ENTITY
            -------------------------

      If Tenant is a business  entity,  then Tenant warrants and represents that
(a) Tenant is duly  organized,  validly  existing and in good standing under the
laws of the jurisdiction in which such entity was organized;  (b) Tenant has the
authority to own its property and to carry on its business as contemplated under
this  Lease;  (c) Tenant is in material  compliance  with all laws and orders of
public  authorities  applicable  to Tenant;  (d) Tenant  has duly  executed  and
delivered this lease;  (e) the execution,  delivery and performance by Tenant of
this Lease (i) are within the powers of Tenant,  (ii) have been duly  authorized
by all  requisite  action,  (iii) will not violate any  provision  of law or any
order of any court or agency of government, or any agreement or other instrument
to which Tenant is a party or by which it or any of its  property is bound,  and
(iv) will not result in the  imposition of any lien or charge on any of Tenant's
property,  except by the provisions of this Lease;  and (f) the Lease is a valid
and binding  obligation of Tenant in  accordance  with its terms.  Tenant,  if a
business entity, agrees that breach of the foregoing warranty and representation
in any material  respect  shall at  Landlord's  election be a default under this
Lease for which there shall be no cure. This warranty and  representation  shall
survive the termination of the Term.

      8.18  DEVELOPMENT OF OTHER PROPERTIES.
            -------------------------------

      Subject to Section  4.1.6,  Landlord  shall have the right,  in connection
with  development  of other land  adjacent to the Building,  to grant  easements
affecting the Land and Building (but not the Premises) for access and egress and
for installation,  maintenance,  repair,  replacement or relocation of utilities
and to subject  the Land and  Building  to such  other  rights,  agreements  and
covenants for such purposes as Landlord may  determine,  provided the same shall
not





                                       

<PAGE>


(i)  unreasonably  interrupt or  unreasonably  interfere  with  Tenant's use and
enjoyment  of the  Premises,  (ii)  reduce the number of the  Exclusive  Parking
Spaces, or (iii) increase Tenant's obligations  hereunder.  Tenant hereby agrees
that this Lease shall be subject and  subordinate  to any such matters  which do
not  unreasonably  interrupt or  unreasonably  interfere  with  Tenant's use and
enjoyment of the Premises. The foregoing sentence shall be self-operative.

      8.19  MISCELLANEOUS PROVISIONS
            ------------------------

      This  Lease may be  executed  in  counterparts  and shall  constitute  the
agreement of Landlord  and Tenant  whether or not their  signatures  appear in a
single copy  hereof.  This Lease shall be construed  as a sealed  instrument  in
accordance with the laws of The  Commonwealth of  Massachusetts.  The titles are
for  convenience  only and  shall not be  considered  a part of the  Lease.  The
enumeration of specific  examples of or inclusions in a general  provision shall
not be construed as a limitation of the general provision.  If Tenant is granted
any extension or other option, to be effective the exercise (and notice thereof)
shall be unconditional;  and if Tenant purports to condition the exercise of any
option or to vary its terms in any manner,  then the purported exercise shall be
ineffective.  Nothing  herein shall be  construed  as creating the  relationship
between  Landlord  and Tenant of  principal  and agent,  or of partners or joint
venturers or any relationship other than landlord and tenant. This Lease and all
consents,  notices,  approvals and all other  documents  relating  hereto may be
reproduced  by  any  party  by  photographic,  microfilm,  microfiche  or  other
reproduction process and the originals thereof may be destroyed;  and each party
agrees that any  reproductions  shall be  admissible in evidence as the original
itself in any judicial or administrative proceeding (whether or not the original
is in existence and whether or not  reproduction  was made in the regular course
of  business)  and that any  further  reproduction  of such  reproduction  shall
likewise be admissible in evidence.


                                   ARTICLE IX

                LANDLORD'S LIABILITY AND ASSIGNMENT FOR FINANCING


      9.1   LANDLORD'S LIABILITY
            --------------------

      Tenant agrees from time to time to look only to Landlord's interest in the
Building for satisfaction of any claim against Landlord hereunder and not to any
other  property or assets of Landlord.  If Landlord from time to time  transfers
its interest in the Building (or part thereof which includes the Premises), then
from and after each such transfer and provided  Tenant  receives notice thereof,
Tenant  shall look solely to the  interests in the Building and the Land of each
of Landlord's  transferees  for the  performance  of all of the  obligations  of
Landlord  hereunder.  The  obligations  of Landlord  shall not be binding on any
members or managers (or partners or trustees or beneficiaries) of Landlord or of
any successor, individually, but only upon Landlord's or such successor's assets
described above.




                                       

<PAGE>


      9.2   ASSIGNMENT OF RENTS
            -------------------

      If, at any time and from time to time,  Landlord assigns this Lease or the
rents  payable  hereunder  to the holder of any  mortgage on the Premises or the
Building,  or to any other  party for the  purpose of  securing  financing  (the
holder of any such mortgage and any other such  financing  party are referred to
herein as the  "Financing  Party"),  whether such  assignment is  conditional in
nature or otherwise, the following provisions shall apply:

            (i) Such  assignment to the  Financing  Party shall not be deemed an
assumption  by the  Financing  Party of any  obligations  of Landlord  hereunder
unless such Financing  Party shall,  by written  notice to Tenant,  specifically
otherwise elect;

            (ii) Except as provided in (i) above,  the Financing  Party shall be
treated as having assumed Landlord's  obligations  hereunder (subject to Section
9.1) only upon  foreclosure of its mortgage (or voluntary  conveyance by deed in
lieu thereof) or the taking of possession of the Premises;

            (iii)  Subject  to  Section  9.1,  the  Financing   Party  shall  be
responsible  for only such  breaches  under the Lease by  Landlord  which  occur
during the period of ownership by the Financing Party after such foreclosure (or
voluntary  conveyance  by deed in lieu  thereof)  or  taking of  possession,  as
aforesaid;

            (iv) In the event Tenant  alleges that  Landlord is in default under
any of Landlord's obligations under this lease, Tenant agrees to give the holder
of any mortgage,  by  registered  mail, a copy of any notice of default which is
served upon the Landlord,  provided  that prior to such notice,  Tenant has been
notified,  in  writing,  (whether  by way of notice of an  assignment  of lease,
request to execute an estoppel letter,  or otherwise) of the address of any such
holder.  Tenant  further  agrees that if Landlord shall have failed to cure such
default  within  the  time  provided  by law or such  additional  time as may be
provided in such  notice to  Landlord,  such holder  shall have thirty (30) days
after the last date on which Landlord could have cured such default within which
such holder will be permitted to cure such  default.  If such default  cannot be
cured within such thirty day period, then such holder shall have such additional
time as may be necessary to cure such default,  if within such thirty day period
such holder has commenced and is diligently  pursuing the remedies  necessary to
effect such cure  (including,  but not limited to,  commencement  of foreclosure
proceedings,  if  necessary,  to effect such cure),  in which event Tenant shall
have no right  with  respect  to such  default  while  such  remedies  are being
diligently pursued by such holder.

      Tenant hereby agrees to enter into such  agreements or instruments as may,
from time to time, be requested in confirmation  of the foregoing,  provided the
Financing Party has entered into a Non-Disturbance Agreement with Tenant.





                                       

<PAGE>


                                    ARTICLE X

                                SECURITY DEPOSIT

      On or before the execution of this Lease, Tenant shall deliver to Landlord
a clean,  irrevocable  letter of credit in the amount of $4,000,000 (the "Letter
of  Credit")  in the  form of  EXHIBIT  C.  Upon the  occurrence  of an Event of
Default,  Landlord  may, but shall not be obligated  to, draw upon the Letter of
Credit to the extent necessary to cure the Event of Default, and Tenant shall be
obligated to reinstate  such security  deposit to the amount then required to be
provided  hereunder.  Subject  to the next  paragraph,  within 30 days after the
expiration or sooner  termination of the Term,  Landlord shall return the Letter
of Credit, to the extent not drawn upon, to Tenant.

      The Letter of Credit,  to the extent not drawn upon,  shall be returned to
Tenant  prior to the time  provided in the  preceding  paragraph  within 30 days
after the delivery to Landlord of evidence that  Tenant's  credit has achieved a
Moody's Investors Service,  Inc. rating of BBB or better. Tenant shall, prior to
applying for a Moody's  rating,  notify Landlord of its intention to apply for a
so-called "shadow" rating and of the anticipated cost thereof.  Provided that no
Event  of  Default  then  exists,   Landlord  shall,  upon  completion  of  such
application,  credit against the next  payment(s) of rent due an amount equal to
one-half  of the actual  costs  reasonably  incurred  by Tenant in  obtaining  a
"shadow" rating by Moody's  Investors  Service,  Inc.  Notwithstanding  anything
herein  to the  contrary,  Landlord's  obligations  pursuant  to  the  foregoing
sentence shall only apply to one (1) application by Tenant; Landlord shall in no
event be responsible for any costs of any subsequent rating applications. If, at
any time after return of the Letter of Credit, such rating shall cease to be BBB
or better,  Tenant shall promptly and in any event within ten business (10) days
following  request therefor by Landlord deliver to Landlord a clean  irrevocable
letter of credit in the amount of  $4,000,000  in the form of EXHIBIT C attached
hereto,  to be held by  Landlord as a security  deposit  and  returned to Tenant
pursuant to this Article.

      The  Letter of Credit  shall be issued  by Fleet  Bank or  another  Boston
clearinghouse bank reasonably  satisfactory to Landlord in Landlord's favor (and
Tenant  shall  provide for  replacements  thereto to be issued and  delivered to
Landlord at least 30 days prior to the expiration of the then  effective  Letter
of Credit,  time being of the  essence),  securing the  performance  of Tenant's
obligations hereunder and payable to Landlord on the terms set forth in the form
attached  to this  Lease as  EXHIBIT  C. The  Letter  of Credit in effect at the
expiration of the Term shall expire no earlier than 30 days after the expiration
of the Term.  Landlord  agrees  that it shall  present  such sight draft only if
Tenant defaults in performance of its obligations hereunder (including a failure
timely to replace an  expiring  letter of credit)  and such  default  shall have
continued  past any  applicable  notice and grace  period.  The Letter of Credit
shall provide for partial draws and shall be assignable by Landlord.



                                       

<PAGE>


                                   ARTICLE XI

                                  SUBORDINATION


      Landlord  shall obtain from any  Financing  Party and any lessor under any
ground  lease or  superior  lease  now or  hereafter  encumbering  or  affecting
Landlord's  interest  in the  Land,  the  Building,  or the  Additional  Land an
agreement  in  recordable  form that,  if such  Financing  Party  forecloses  or
otherwise  exercises it rights under its mortgage,  or if such lessor terminates
or  otherwise  exercises  its rights under its lease,  or either such  Financing
Party or such lessor  otherwise  acquires  Landlord's  interest in the Land, the
Building or the Additional  Land,  such Financing Party and/or such lessor shall
recognize Tenant's rights and not disturb Tenant's occupancy of the Premises and
the  Exclusive  Parking  Spaces  under the terms and  conditions  of this  Lease
(provided that nothing herein shall be construed to limit such Financing Party's
and/or lessor's  rights to exercise the rights of Landlord  hereunder) and shall
assume and perform Landlord's  obligations under this Lease (each such agreement
being a  "Non-Disturbance  Agreement").  If Landlord  obtains a  Non-Disturbance
Agreement  from each such  Financing  Party and/or  lessor,  this Lease shall be
subject  and  subordinate  to any  mortgages  or ground  leases  that may now or
hereafter  be  placed  upon  the  Building  and/or  the  Land and to any and all
advances to be made under such  mortgages  or ground  leases and to the interest
thereon,  and all renewals,  extensions and consolidations  thereof on the terms
and conditions  set forth in the  Non-Disturbance  Agreement;  provided that any
mortgagee  or ground  lessor  may elect to have this  Lease a prior  lien to its
mortgage or ground lease and in the event of such election and upon notification
by such mortgagee or ground lessor to Tenant to that effect, this Lease shall be
deemed prior in lien to said  mortgage or ground  lease.  This Section  shall be
self-operative,  but in confirmation  thereof,  Tenant shall execute and deliver
whatever instruments (such instruments to be in recordable form) may be required
to  acknowledge   such   subordination   or  priority  in  accordance  with  any
Non-Disturbance  Agreement.  Tenant also  agrees  this Lease  shall  survive any
merger of the estates of ground lessor and ground lessee under any ground lease.


                                   ARTICLE XII

                                     PARKING

      Throughout  the Term,  Tenant shall have, as  appurtenant to the Premises,
the right  without  charge to use, in common only with Landlord (as necessary to
perform Landlord's  obligations hereunder) and other tenants of the Building and
invitees  thereof,  987 parking spaces (the "Exclusive  Parking  Spaces") on the
Land and the Additional Land for its employees and business  invitees.  Such use
shall  be  subject  to  reasonable  rules  and  regulations  from  time  to time
established  by  Landlord.  If the  Building  is at any time  occupied  by other
tenants in addition to Tenant,  such rules and  regulations  shall provide for a
reasonable  allocation  of such  spaces  among all  tenants of the  Building  in
proportion to their share of the Rentable Floor Area of the Building.

      Landlord  represents  that it has a leasehold  interest in additional land
abutting the Land (the "Additional  Land") under a ground lease between Landlord
and Albert L. Nardone and




                                       

<PAGE>


Anthony B.  Nardone as Trustees of Five  Robbins  Realty  Trust dated of even or
near even date herewith (the "Ground Lease") (a copy of which is attached hereto
as Exhibit D). On or before May 1, 1997,  Landlord  shall  construct 307 parking
spaces on the  Additional  Land in accordance  with a site plan  entitled  "Site
Plans;  Proposed Parking  Improvements" dated July 3, 1996 and prepared by Rizzo
Associates,  Inc.  Tenant  shall  have,  as  appurtenant  to the  Premises,  the
exclusive  right to use such  spaces  during  the Term.  If  Landlord  elects to
exercise  its purchase  option under  Article VII of the Ground Lease during the
term of this Lease,  Landlord shall,  promptly  following delivery to the ground
lessor of the Option Notice (as defined in the Ground Lease),  deliver a copy of
such Option Notice to Tenant. Upon determination of the Purchase Price under the
Ground Lease,  Landlord shall promptly  notify Tenant of such Purchase Price. If
Landlord  exercises such option during the Term of this Lease,  Tenant shall, on
or before the date ten (10) business days prior to the closing date set forth in
the Option Notice,  pay to Landlord as additional rent an amount equal to 50% of
the amount by which (a) the sum of the Ground Lease  Payments (as defined below)
and the Purchase Price exceeds (b)  $250,000.00.  "Ground Lease  Payments" shall
mean all Fixed Rent (as defined  under the Ground  Lease) and real estate  taxes
paid  by  Nashoba  View  Associates,   LLC  under  the  Ground  Lease  from  the
commencement  date thereof  through the closing date.  Landlord shall provide to
Tenant an accounting of the Ground Lease Payments promptly following delivery of
the Option  Notice.  If Landlord  exercises  such option during the Term of this
Lease, the term "Land" as used herein shall,  upon acquisition of the Additional
Land, thereafter be construed to include the Additional Land.

      Subject to Tenant's payments pursuant to the foregoing paragraph, Landlord
shall pay and perform fully its  obligations  under the Ground  Lease.  Landlord
shall  promptly  provide Tenant with a copy of a notice of a default by Landlord
in its obligations  under the Ground Lease. If Landlord  defaults in the payment
or performance of any of its obligations under the Ground Lease and such default
continues  after any  applicable  notice and/or the expiration of any applicable
grace period under the Ground Lease,  Tenant may, but shall not be obligated to,
pay such sums  and/or  take  such  actions  as may be  reasonably  necessary  or
appropriate to cure such default of Landlord, any amounts reasonably expended by
Tenant in  effecting  such cure shall be  reimbursed  by Landlord to Tenant.  If
Landlord fails to reimburse  Tenant for any such amounts within thirty (30) days
after Landlord  receives a written demand therefor,  Tenant shall have the right
to apply  such  amounts  as a credit  against  payments  of Annual  Fixed  Rent,
additional  rent and other charges due from Tenant to Landlord under this Lease,
provided  that in no event shall the amount so credited  in any  calendar  month
exceed one-third of the quarterly ground rent due under the Ground Lease.



                                  ARTICLE XIII

                                  SEPTIC SYSTEM


Tenant hereby  acknowledges the terms and conditions of the DEP Letter.  Without
limiting the generality of any other of Tenant's  obligations  contained herein,
Tenant shall neither use or permit any use of the Premises  which is contrary to
applicable  law  regarding the Septic  System.  Notwithstanding  the  foregoing,
Tenant shall have the right, after giving written notice to







                                       

<PAGE>


Landlord and subject to the  conditions  stated below,  to contest in good faith
the validity of any requirement of DEP with respect to the Septic System. During
the  pendency of such  contest,  Tenant shall not be required to comply with any
such requirement  provided that Tenant shall indemnify and save Landlord and the
Indemnitees (as defined in Section 5.5) harmless from all injury,  loss, claims,
liens or damage  resulting  from the delay in such  compliance  and/or  Tenant's
contest of such requirement.












                                       

<PAGE>

      Executed to take effect as a sealed instrument.


                                    LANDLORD

                                    NASHOBA VIEW ASSOCIATES, LLC


                                    By: /s/ Donald J. Chiofaro,
                                        -----------------------------------
                                        Donald J. Chiofaro,
                                        Manager


                                    TENANT

                                    CASCADE COMMUNICATIONS CORP.


                                    By: /s/ Paul E. Blondin
                                        -----------------------------------
                                        Paul E. Blondin
                                        Chief Financial Officer