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                                                                    EXHIBIT 23.3
 
                                                                 January 9, 1996
 
Genome Therapeutics Corp.
100 Beaver Street
Waltham, Massachusetts 02154
 
Re:  Genome Therapeutics Corp.
     Registration Statement on Form S-3
 
Dear Sirs:
 
     We hereby consent to the use of our name under the caption "Experts" in
Genome Therapeutics Corp.'s Registration Statement on Form S-3 and in the
related prospectus.
 
                                            Very truly yours,
 
                                            /S/  LAHIVE & COCKFIELD
                                            ....................................
 
                                            Lahive & Cockfield