EXHIBIT 5.1 [LETTERHEAD OF CAHILL GORDON & REINDEL] June 28, 1996 (212) 701-3000 XOMA Corporation 2910 Seventh Street Berkeley, California 94710 Ladies and Gentlemen: As counsel for XOMA Corporation (the "Company"), we are representing the Company in connection with the registra- tion statement on Form S-3 (the "Registration Statement") filed with the Securities and Exchange Commission (the "Commission") on June 28, 1996 relating to the registration under the Securi- ties Act of 1933, as amended (the "Act"), of 1,500,000 shares (the "Shares") of the Company's Common Stock, par value $.0005 per share. We advise you that in our opinion the Shares were validly issued and are fully paid and non-assessable. We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement. We also consent to the reference under the heading "Legal Opin- ions" in the Registration Statement to our having passed upon the legal matters referred to above. Our consent to such ref- erence does not constitute a consent under Section 7 of the Act, as in consenting to such reference we have not certified any part of the Registration Statement and do not otherwise come within the categories of persons whose consent is required under said Section 7 or under the rules and regulations of the Commission thereunder. Very truly yours, CAHILL GORDON & REINDEL