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                                                                   Exhibit 10.11

                             GENETICS INSTITUTE, INC.

                               Second Amendment to

                        1991 Employee Stock Purchase Plan
                        ---------------------------------

        The Genetics Institute, Inc. (the "Company") 1991 Employee Stock
Purchase Plan (the "Plan") is hereby amended in the following respect.

        1.   Section 4 of the Plan is deleted in its entirety and the following
is substituted therefor:

        "The Plan will be implemented through a continuous series of offerings
of the Common Stock (individually, an "Offering").  Each Offering will be for a
period of twenty-four months (an "Offering Period").  Offerings will commence
every six months on November 15 and May 15 of each year and shall end on the
second November 14 and May 14, respectively; PROVIDED, HOWEVER, the next
Offering under the Plan shall commence on June 15, 1994 and end on May 14,
1996.  The last Offering will commence on November 15, 1996 and end on November
14, 1998.  Each Offering Period will consist of four consecutive six-month
purchase periods (individually, a "Purchase Period").  Each six-month Purchase
Period shall commence on each May 15 and November 15 and shall end on the next
succeeding November 14 or May 14.  The Purchase Periods currently scheduled to
terminate on June 14, 1994 shall terminate on such date, but the Purchase
Periods currently scheduled to terminate on December 14, 1994 for the Offerings
then in effect shall instead terminate on November 14, 1994.  The Purchase
Periods currently scheduled to commence on June 15, 1994 shall commence on such
date, but the Purchase Periods currently scheduled to commence on December 15,
1994 for the Offerings then in effect shall instead commence on November 15,
1994.  The last day of each Purchase Period shall be the "Purchase Date" for
that "Purchase Period."

        2.   The last sentence of Section 8(a) is hereby deleted and the
following sentence is substituted therefor:

        "Any excess payroll deductions in his or her account at that time will
be returned to such participant."

        3.   Section 13(a) is hereby deleted and the following is substituted
therefor:

        "Subject to adjustment as provided in Paragraph 18, the maximum number
of shares of Common Stock which shall be issued under the Plan is 480,000
shares.  Subject to adjustment as provided in Paragraph 18, the maximum number
that may be issued during each Purchase Period for all Offerings then in effect
is

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50,000 shares.  If the total number of shares for which Options are
exercised on any Purchase Date in accordance with Paragraph 8 exceeds the
maximum number available, the Company shall make a pro rata distribution in as
nearly a uniform manner as shall be practicable and as it shall determine to be
equitable, and the balance of payroll deductions shall be returned to the
participants.  If the total number of shares for which Options are exercised on
any Purchase Date in accordance with Paragraph 8 is less than the maximum
number available, the number of shares not purchased may be carried over to and
made available during any subsequent Offering."


                                        Adopted by the Board of Directors 
                                        on 
                                        January 18, 1994

                                        Approved by the Stockholders of the 
                                        Company on April 19, 1994