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                                 FIRST AMENDMENT

                                       TO

                          SHAREHOLDER RIGHTS AGREEMENT

                                January __, 2000

         First Amendment to that certain Shareholder Rights Agreement, (the
"Agreement"), made as of October 21, 1999, between CORE, INC., a Massachusetts
corporation (the "Company"), and State Street Bank and Trust Company, a
Massachusetts chartered trust company (the "Rights Agent").

         Capitalized terms used herein and not otherwise defined will have the
meanings ascribed to them in the Agreement.

         WHEREAS, pursuant to the provisions of Section 27 of the Agreement,
prior to the occurrence of a Section 11(a)(ii) Event, the Company and the Rights
Agent shall, if the Board of Directors of the Company so directs, supplement or
amend any provision of this Agreement as the Board of Directors of the Company
may deem necessary or desirable without the approval of any holders of
certificates representing shares of Common Stock of the Company;

         WHEREAS, as of the date hereof there has not occurred a Section
11(a)(ii) Event;

         WHEREAS, on December 21, 1999, the Board of Directors of the Company
voted to amend the Agreement with respect to ownership of shares of the Common
Stock of the Company by Gilder Gagnon Howe & Co., LLC and Gagnon Securities;

         NOW, THEREFORE, pursuant to the provisions of Section 27 of the
Agreement, the Company and the Rights Agent hereby agree as follows:

         1. The Agreement is hereby amended so that Gagnon Securities shall be
deemed to be a "Grandfathered Person" under the Agreement. In furtherance
thereof, the Company and the Rights Agent hereby amend SECTION 1(q) of the
Agreement so that, as amended, it shall read in its entirety as follows:

         "(q) "GRANDFATHERED PERSON" shall mean any of (i) Gilder Gagnon Howe &
         Co., LLC, (ii) Warburg, Pincus Asset Management, Inc. or (iii) Gagnon
         Securities, or any of their respective Affiliates or Associates,
         PROVIDED, HOWEVER, that any Affiliate or Associate of Gagnon Securities
         shall be deemed to be a Grandfathered Person only during such time as
         such Person continues to be an Affiliate or Associate of Gagnon
         Securities."


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         2. The Agreement is hereby amended so that the "Grandfathered
Percentage" of Gagnon Securities under the Agreement shall be twenty (20%)
percent of the outstanding shares of Common Stock of the Company. In furtherance
thereof, the Company and the Rights Agent hereby amend SECTION 1(p) of the
Agreement so that, as amended, it shall read in its entirety as follows:

         "(p) "GRANDFATHERED PERCENTAGE" shall mean, (i) with respect to any
         Grandfathered Person other than Gagnon Securities or any of its
         Affiliates or Associates, the percentage of the outstanding shares of
         Common Stock that such Grandfathered Person, together with all
         Affiliates and Associates of such Grandfathered Person, beneficially
         owns as of the Grandfathered Time plus an additional two percent (2%)
         and (ii) with respect to Gagnon Securities or any of its Affiliates or
         Associates, twenty (20%) percent; provided, however, that, in the event
         any Grandfathered Person other than Gagnon Securities or any of its
         Affiliates or Associates shall sell, transfer, or otherwise dispose of
         any outstanding shares of Common Stock after the Grandfathered Time,
         the Grandfathered Percentage shall, subsequent to such sale, transfer
         or disposition, mean, with respect to such Grandfathered Person, the
         lesser of (i) the Grandfathered Percentage as in effect immediately
         prior to such sale, transfer or disposition or (ii) the percentage of
         outstanding shares of Common Stock that such Grandfathered Person
         beneficially owns immediately following such sale, transfer or
         disposition plus an additional two percent (2%)."

         3. The Agreement is hereby amended so that the "Grandfathered
Percentage" of Gagnon Securities under the Agreement shall be twenty (20%)
percent of the outstanding shares of Common Stock of the Company. In furtherance
thereof, the Company and the Rights Agent hereby amend SECTION 1(a) of the
Agreement by striking the final sentence of the first paragraph of SECTION 1(a)
and replacing it with the following sentence:

         "Any Grandfathered Person who after the Grandfathered Time becomes the
         Beneficial Owner of less than 15% of the shares of Common Stock of the
         Company then outstanding shall cease to be a Grandfathered Person;
         PROVIDED, HOWEVER, that the provisions of this sentence shall not apply
         to Gagnon Securities or any of its Affiliates or Associates."

         4. Except as otherwise expressly provided herein, all provisions of the
Agreement shall remain in full force and effect.


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         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed as an instrument under seal and attested, all as of the day and
year first above written.

Attest:                                      CORE, INC.

By:                                          By:
   -----------------------------                --------------------------------

                                             Name:
                                                  ------------------------------

                                             Title:
                                                   -----------------------------


Attest:                                      STATE STREET BANK AND
                                             TRUST COMPANY, as rights agent


By:                                          By:
   -----------------------------                --------------------------------

                                             Name:
                                                  ------------------------------

                                             Title:
                                                   -----------------------------


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