PLEDGE AGREEMENT


        PLEDGE AGREEMENT dated as of September 24, 1998 by and between Owen A.
Dempsey, an individual with an address at 21 Harris Street, Brookline,
Massachusetts 02146 (the "Pledgor"), in favor of Endogen, Inc., a Massachusetts
corporation, having its principal place of business at 30 Commerce Way, Woburn,
Massachusetts 01801 ("Endogen").

        WHEREAS, Endogen has agreed to lend to the Pledgor $36,000.00 (the
"Loan"), which Loan is evidenced by a secured promissory note in the principal
amount of $36,000.00 of the Pledgor to Endogen dated as of the date hereof (the
"Note"); and

        WHEREAS, the obligation of Endogen to grant the Loan is subject to the
condition that the Pledgor execute and deliver this Pledge Agreement and grant
the security interest hereinafter described.

        NOW, THEREFORE, in consideration of the covenants and conditions set
forth herein and to induce Endogen to grant the Loan, the Pledgor hereby agrees
with Endogen as follows:

        Section 1. Defined Terms. The following terms have the following
meanings:

        "Code" means the Uniform Commercial Code from time to time in effect in
the Commonwealth of Massachusetts.

        "Collateral" means the Pledged Stock and all Proceeds.

        "Foreclosure Date" means any date on which Endogen sends to the Pledgor
a Foreclosure Notice.

        "Foreclosure Notice" means notice that Endogen may give to the Pledgor
when an Event of Default occurs and is continuing, which notice shall state (i)
that Endogen is exercising its rights under this Pledge Agreement, (ii) the
nature of the Event of Default.

        "Loan" means the loan by Endogen of $36,000.00 in favor of the Pledgor.

        "Pledge Agreement" means this Pledge Agreement, as amended, supplemented
or otherwise modified from time to time.

        "Pledged Stock" means 12,000 shares of Endogen Common Stock owned by the
Pledgor.

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        "Proceeds" means all "proceeds" as such term is defined in Section
9-306(1) of the Uniform Commercial Code in effect in Massachusetts on the date
hereof and, in any event, includes, without limitation, all dividends or other
income from the Pledged Stock, collections thereon or distribution with respect
thereto.

        Section 2. Pledge; Grant of Security Interest. The Pledgor grants to
Endogen a first security interest in the Collateral, as collateral security for
the prompt and complete payment of the Note in accordance to its terms. The
Pledgor shall deliver to Endogen the stock certificate or certificates
representing the Pledged Stock to be held in escrow by Endogen until the Note is
paid in full, together with an undated stock power or powers covering such
certificate or certificates, duly executed in blank.

        Section 3. Representations and Warranties. The Pledgor represents and
warrants that:

               (a) this Pledge Agreement has been duly executed by the Pledgor,
                   and constitutes a legal, valid and binding obligation of the
                   Pledgor enforceable in accordance with its terms;

               (b) no consent or authorization of, filing with, or other act by
                   or with respect to, any arbitrator or governmental authority
                   and no consent of any other person (including without
                   limitation, any creditor of the Pledgor), is required in
                   connection with the execution, delivery, performance,
                   validity or enforceability of this Pledge Agreement; and

               (c) the Pledgor is the record and beneficial owner of the Pledged
                   Stock, and the Pledged Stock is free of any and all liens,
                   pledges, security interests, encumbrances or options in favor
                   of, or claims of, any other person, except the lien created
                   by this Pledge Agreement.

        Section 4. Covenants. The Pledgor covenants and agrees with Endogen
that, from and after the date of this Pledge Agreement until the Note is paid in
full:

               (a) At any time and from time to time, upon written request of
                   Endogen, and at the sole expense of the Pledgor, the Pledgor
                   shall promptly and duly execute and deliver such further
                   instruments and documents and take such further actions as
                   Endogen may reasonably request for the purposes of obtaining
                   or preserving the full benefits of this Pledge Agreement and
                   of the rights and powers herein granted. If any amount
                   payable under or in connection with any of the Collateral is
                   or becomes evidenced by a promissory note, other instrument
                   or chattel paper, such note, instrument or chattel paper
                   shall be promptly delivered to Endogen, duly endorsed in a
                   manner satisfactory to Endogen, to be held as Collateral
                   pursuant to this Pledge Agreement.


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               (b) The Pledgor agrees to pay, and to save Endogen harmless from,
                   any and all liabilities with respect to, or resulting from
                   any delay in paying, any and all stamp, excise, sales or
                   other taxes which may be payable or determined to be payable
                   with respect to any of the Collateral or in connection with
                   any of the transactions contemplated by this Pledge
                   Agreement.

        Section 5. Cash Dividends; Voting Rights. Unless an Event of Default has
occurred and is continuing and Endogen has given a Foreclosure Notice to the
Pledgor, the Pledgor shall be permitted to receive all cash dividends paid by
Endogen with respect to the Pledged Stock and shall possess all rights to vote
the Pledged Stock at any meeting of shareholders of Endogen or otherwise.

        Section 6. Default. The failure by the Pledgor to pay any amount due and
payable under the Note within ten (10) business days after such amount becomes
due and payable shall constitute a default hereunder (an "Event of Default").

        Section 7. Rights of Endogen. (a) If an Event of Default occurs and is
continuing and Endogen gives a Foreclosure Notice to the Pledgor (i) Endogen
shall have the right to receive any and all cash dividends paid with respect to
the Pledged Stock and make application thereof to the Note in such order as it
may determine, and (ii) all shares of the Pledged Stock shall be registered in
the name of Endogen or its nominee, and Endogen or its nominee may thereafter
exercise (A) all voting, corporate and other rights pertaining to such shares of
the Pledged Stock at any meeting of shareholders of Endogen or otherwise and (B)
any and all rights of conversion, exchange, subscription and any other rights,
privileges or options pertaining to the Pledged Stock as if it were the absolute
owner thereof (including, without limitation, the right to exchange at its
discretion any and all of the Pledged Stock upon the merger, consolidation,
reorganization, recapitalization or other fundamental change in the corporate
structure of Endogen, or upon the exercise by the Pledgor or Endogen of any
right, privilege or option pertaining to such shares of the Pledged Stock, and
in connection therewith, the right to deposit and deliver any and all of the
Pledged Stock with any committee, depository, transfer agent, registrar or other
designated agency upon such terms and conditions as it may determine), all
without liability except to account for property actually received by it, but
Endogen shall have no duty to exercise any such right, privilege or option and
shall not be responsible for any failure to do so or delay in so doing.

Upon the occurrence of an Event of Default, Endogen shall have the rights and
remedies set forth in this Section 7 and in any other instrument or agreement
evidencing or relating to the Loan, and all rights and remedies of a secured
party under the Code or other applicable law. The Pledgor shall remain
personally liable to the Company with respect to all of the obligations under
that certain "full recourse" Note of even date herewith.


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        (b)    Endogen shall not be under any obligation to sell of otherwise
               disposeof any Collateral upon request of the Pledgor or any other
               person or take any other action whatsoever with regard to the
               Collateral or any part thereof.

        (c)    When the Note has been paid in full, the pledge of the
               Collateral shallcease, and the Collateral shall revert to the
               Pledgor free and clear of all liens securing any obligation or
               liability of the Pledgor to Endogen, and Endogen's rights, title,
               and interest therein shall cease and become void.

        Section 8. Severability. Any provision of this Pledge Agreement that is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

        Section 9. No Waiver; Cumulative Remedies. No failure to exercise, nor
any delay in exercising, on the part of Endogen, any right, power or privilege
hereunder shall operate as a waiver thereof. No single or partial exercise of
any right, power or privilege hereunder shall preclude any other or further
exercise thereof or the exercise of any other right, power or privilege. The
rights and remedies herein provided are cumulative, may be exercised singly or
concurrently and are not exclusive of any rights or remedies provided by law.

        Section 10. Waivers and Amendments; Successors and Assigns; Governing
Law. None of the terms or provisions of this Pledge Agreement, may be waived,
amended, supplemented or otherwise modified except by a written instrument
executed by the Pledgor and Endogen, provided, that any provision of this Pledge
Agreement may be waived by Endogen in a letter or agreement executed by Endogen.
This Pledge Agreement shall be binding upon the successors and assigns of the
Pledgor and shall inure to the benefit of Endogen and its successors and
assigns. This Pledge agreement shall be governed by and construed and
interpreted in accordance with, the laws of the Commonwealth of Massachusetts.
Each party hereto consents to the jurisdiction of the state courts of the
Commonwealth of Massachusetts and the United States courts for the District of
Massachusetts with respect to the transactions contemplated hereby.

        Section 11. Notices. Notices under this Pledge Agreement may be given by
express overnight courier service or by facsimile transmission, addressed to the
Parties at their respective addresses set forth in the first paragraph to this
Pledge Agreement and shall be effective when sent. Either party may change their
respective addresses by written notice to the other party.

        Section 12.  Counterparts.  This Pledge Agreement may be executed in
several counterparts, each of which shall constitute an original, but all of
which, when taken together, shall constitute but one agreement.


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        IN WITNESS WHEREOF, the undersigned has caused this Pledge Agreement to
be duly executed and delivered as of the date first above.


                                          PLEDGOR:


                                          /s/Owen A. Dempsey
                                          ---------------------------
                                          Owen A. Dempsey


                                          ENDOGEN, INC.


                                          /s/Avery W. Catlin
                                          ----------------------------
                                          Avery W. Catlin
                                          Vice President, Operations & Finance