LEASE TERMINATION AGREEMENT

     THIS, LEASE TERMINATION AGREEMENT ("Agreement") is made as of the day of
the 31st day of May , 1996 by and between MASSACHUSETTS INSTITUTE OF TECHNOLOGY
("Lessor"), a Massachusetts educational corporation with an address of 238 Main
Street, Suite 200, Cambridge, Massachusetts 02142 and ENDOGEN, INCORPORATED
("Lessee") , a Delaware corporation with an address of 640 Memorial Drive,
Cambridge, Massachusetts 02139.


                                 R E C I T A L

     A. Pursuant to a lease dated August 10, 1993 (as amended, the "Lease"),
Lessor leased to Lessee a portion of the third floor of Lessor's building at 640
Memorial Drive, Cambridge, Massachusetts. Capitalized terms used in this
Agreement which are defined in the Lease and not otherwise defined herein shall
have the same meaning herein as therein.

     B. Lessee has occupied the Premises pursuant to the Lease but now wishes to
vacate the Premises and to terminate the Lease.

     C. Lessor is willing to agree to the termination of the Lease upon the
terms and conditions herein provided.

      NOW  THEREFORE,  for good and  valuable  consideration,  the  receipt  and
sufficiency of which is hereby  acknowledged,  Lessor and Lessee hereby agree as
follows:

     1. Lessee shall vacate the Premises on a phased basis, commencing on or
about June 14, 1996 and ending not later than August 14, 1996.

     2. On or about June 14, 1996, Millenium Pharmaceuticals, Inc.
("Millennium") shall be construct within the Premises on the third floor of the
Building, at no cost to Lessee, temporary demising partitions dividing the
Premises into two areas, one of which shall consist of approximately- 10,000
square feet of rentable area (the "First Occupied Area") , and the other of
which shall comprise the balance of the Premises on the third floor of the
Building (the "Second Occupied Area") . Lessee shall permit such access to the
Premises for Millennium, its contractors, subcontractors and agents, as is
necessary for the construction of such temporary demising partitions.

     3. Lessee shall vacate the First Occupied Area and surrender and redeliver
it to Lessor in the condition required by the terms of the Lease by June 14,
1996. Upon the redelivery of the First Occupied Area to Lessor, Lessor shall
promptly inspect the same and determine whether it has been redelivered in
accordance with the terms of the Lease. Lessor shall thereafter



promptly notify Lessee whether it accepts the surrender of the First occupied 
Area. Immediately upon Lessor's acceptance of the surrender of the First 
Occupied Area, the Lease shall be deemed to be amended so as to delete the
First Occupied Area from the Premises for all purposes of the Lease except as
otherwise provided in this Agreement.

     4. Lessee shall vacate the Second Occupied Area and surrender and redeliver
it to Lessor in the condition required by the terms of the Lease by August 14,
1996. Upon the redelivery of the Second Occupied Area to Lessor, Lessor shall
promptly inspect the same and determine whether it has been redelivered in
accordance with the terms of the Lease. Lessor shall thereafter promptly notify
Lessee whether it accepts the surrender of the Second Occupied Area. Immediately
upon Lessor's acceptance of the surrender of the Second occupied Area, the Lease
shall terminate in its entirety with the same effect as if the Term had expired
on the date of Lessor's acceptance of such surrender, except that those
provisions of the Lease which by their terms survive the expiration of the Term
(e.g., Section 12(m)) shall survive such termination. Notwithstanding anything
to the contrary herein contained, Lessee shall vacate the entire Premises
(including, without limitation, the Basement Space) and surrender and redeliver
it to Lessor in the condition required by the terms of the Lease by August 14,
1996.

     5 . On or prior to June 14, 1996, Lessee shall yield up and relinquish to
Lessor fifteen (15) of the parking spaces leased by Lessee pursuant to Section
10.1 of the Lease, which spaces shall then be available for re-lease by Lessor
to a third party.

     6 . Until such time as Lessor accepts the surrender and redelivery of the
First Occupied Area, the Lease shall remain in full force and effect regardless
of whether or not Lessee actually occupies all or any portion of the First
Occupied Area. From and after the date on which Lessor accepts the surrender of
the First Occupied Area, Lessee's obligations under the Lease to pay Basic Rent,
Taxes and Operating Expenses to Lessee shall be pro-rated to reflect the partial
termination of the Lease as to the First Occupied Area except that Lessee shall
remain obligated to pay for all electricity consumed in the Premises, whether by
Lessee or by others, but Lessee shall have the right to collect from Millennium
its pro-rata share of such electric charges. Lessee shall remain obligated to
pay Basement Rent in accordance with the terms of the Lease until Lessor has
accepted the surrender of the Basement Space.

     7 . All Alterations to the Premises made, installed or constructed on
behalf of Lessee, and all of Lessee's Work shall remain in or on the Premises
notwithstanding the termination of the Lease as herein provided. Provided that
the Lease is terminated pursuant to the terms of this Agreement, Lessor hereby
agrees to reimburse Lessee for the undepreciated cost of the



                                       2



Alterations and Lessee's Work (determined on a straight-line basis) which
shall remain in the Premises, by making thirty-three (33) equal monthly payments
of $10,727.00 each to Lessee on the first day of each month, commencing on July
1, 1996 and ending on March 1, 1999, inclusive. [Amount of payments is subject
to verification by Lessor of undepreciated costs and timely execution of
documents.]

      8.  Notwithstanding  anything  contained  herein  to  the  contrary,  this
Agreement shall not be effective unless and until all of the following occur:

     (a) Lessor unconditionally delivers to Lessee an executed counterpart of
this Agreement;

     (b) Lessor receives a written waiver from Lifeline Systems, Inc. of its
right of offer with respect to the proposed lease of the Premises by Lessor to
a third party;

     (c) Lessor receives a written waiver from Pathology Services, Inc. of its
right of offer with respect to the proposed lease of the Premises by Lessor to a
third party; and

     (d) Lessor unconditionally delivers to such third party a written agreement
executed by Lessor leasing the Premises to such third party.

 Lessee acknowledges that Lessor's willingness to enter into this Agreement
is based, in part, on Lessor's expectation that third parties over whom Lessor
has no control will take the actions described above in this Paragraph. Lessor
makes no representation or warranty concerning whether or not such third parties
will take such actions so that the foregoing conditions to the effectiveness of
this Agreement are satisfied in full.

     9 . It shall constitute an Event of Default under the Lease, for which no
notice is required or cure period allowed, if Lessee either (i) fails to
surrender and redeliver the First Occupied Area to Lessor in the condition
required by the terms of the Lease by June 14, 1996, or (ii) fails to surrender
and redeliver the entire Premises to Lessor in the condition required by the
terms of the Lease by August 14, 1996. In the event of the occurrence of such an
Event of Default, or any other Event of Default under the Lease, then, in
addition to the rights and remedies of Lessor as provided in the Lease, Lessor
shall have the right, by notice given to Lessee, to terminate this Agreement,
whereupon the Lease shall remain in full force and effect as if this Agreement
had never been executed.

     10. The Security Deposit shall be accounted for and, to the extent
applicable, refunded to Lessee, in accordance with the provisions of Section
25.0 of the Lease, within thirty (30) days


                                       3



of the termination of the Lease in its entirety as herein provided.

     11. Contemporaneously with its execution of this Agreement, Lessee shall
furnish to Lessor a certified copy of the resolution of the Board of Directors
of Lessee authorizing Lessee to enter into this Agreement.

     12. This Agreement constitutes the entire agreement of the parties with
respect to its subject matter, and no oral statement or prior written matter
shall have any force or effect. This Agreement shall not be modified or canceled
except by writing subscribed to by all parties. This Agreement shall be governed
by and construed in accordance with the laws of the Commonwealth of
Massachusetts.

     EXECUTED under seal as of the day and year first above written.


            LESSOR:                    MASSACHUSETTS INSTITUTE OF
                                          TECHNOLOGY


Date: 6/12/    ,1996             By: /s/ Philip A. Trussell
                                     --------------------------------------
                                         Philip A. Trussell
                                         Director of Real Estate
                                         Hereunto duly authorized



LESSEE:                     ENDOGEN, INCORPORATED





Date: 5/31     ,1996              By: /s/ Owen A. Dempsey
                                      --------------------------------------
                                      Owen A. Dempsey
                                      President and Chief 
                                      Executive Officer
                                      Hereunto duly authorized