EXHIBIT 4.2

                                    AMENDMENT
                                     TO THE
                        1996 EMPLOYEE STOCK PURCHASE PLAN
                       OF MICROCIDE PHARMACEUTICALS, INC.


         Pursuant to the authority reserved to the Board of Directors (the
"Board") of Microcide Pharmaceuticals, Inc., a corporation organized under the
laws of the State of Delaware (the "Company"), under Section 19(a) of the
Company's 1996 Employee Stock Purchase Plan, as amended (the "Plan"), the Board
hereby amends the Plan as follows:

        1.   Stock Subject to the Plan.  The first sentence of Section 12(a) of
             -------------------------
the Plan is amended to read in its entirety as follows:

                "The maximum number of shares of the Company's Common Stock
which shall be made available for sale under the Plan shall be four hundred
seventy thousand (470,000) shares, subject to adjustment upon changes in
capitalization of the Company as provided in Section 18 hereof."

                               * * * * * * * * * *

        I hereby certify that the foregoing Amendment to the Plan was duly
adopted by the Board of Directors of Microcide Pharmaceuticals, Inc., effective
as of May 1, 2001, and was approved by the shareholders of the Company at the
Annual Meeting of Shareholders on June 21, 2001, as required under applicable
state and federal law.

         Executed on this 18th day of October, 2001.



                                    /s/ Alan C. Mendelson
                                    -----------------------------------
                                    Alan C. Mendelson, Secretary