EXHIBIT 24.2


  [LETTERHEAD OF MARSHALL, O'TOOLE, GERSTEIN, MURRAY & BORUN]



                         May 13, 1996


Board of Directors
XOMA Corporation
2910 Seventh Street
Berkeley, CA 94710

            Re:  Registration Statement on Form S-3
                 ----------------------------------

Gentlemen:

          Marshall, O'Toole, Gerstein, Murray & Borun hereby
consents to the disclosure of our relationship as patent coun-
sel to XOMA Corporation (the "Company") in the Company's Regis-
tration Statement on Form S-3 (the "Registration Statement"),
and in particular the references to us under the headings "Risk
Factors - No Assurance of Patent Protection/Avoidance of Patent
Infringement" and "Legal Opinions," and to the filing of this
consent as an exhibit to the Registration Statement.

                              Very truly yours,



                              Marshall, O'Toole, Gerstein
                                Murray & Borun