SecProbe.io

Via Facsimile and U.S. Mail
Mail Stop 6010

         November 19, 2007

Steven B. Engle
President and Chief Executive Officer
XOMA Ltd.
2910 Seventh Street
Berkeley, CA 94710

Re:   XOMA Ltd.
 Form 10-K for the Fiscal Year Ended December 31, 2006
 Filed March 8, 2007
 Form 10-Q for the Quarterly Period Ended September 30, 2007
 Filed November 8, 2007
 File Number:  000-14710

Dear Mr. Engle:

We have reviewed your filings and have the following comments.  In our
comments, we ask you to provide us with  information to better understand your
disclosures.  Where a comment requests you to revise disclosure, the information you
provide should show us what the revised disc losure will look like and identify the annual
or quarterly filing, as appli cable, in which you intend to fi rst include it.  If you do not
believe that revised disclosure  is necessary, explain the reason in your response.  After
reviewing the information provided, we may raise additional comments and/or request
that you amend your filings.

 Please understand that the purpose of our re view process is to assist you in your
compliance with the applicable disclosure  requirements and to  enhance the overall
disclosure in your filings.  We look forward to working with you in these respects.  We
welcome any questions you may have about our  comments or on any other aspect of our
review.  Feel free to call us at the telephone numbers listed at the end of this letter.

Form 10-K for the fiscal year ended December 31, 2006
 Current Agreements, page 7

Steven B. Engle
XOMA Ltd. November 19, 2007 Page 2  1. The agreements with the following compan ies do not appear to be filed as
exhibits: Lexicon, NIAID, Taligen, AVE O, Attenuon, and Triton.  Please provide
us with an analysis supp orting your determination that  you are not substantially
dependent on each of these agreements.

Liquidity and Capital Resources, page 46

2. Please revise your note to the table of contractual obligations to include the
aggregate amount of potential milestone pa yments along with a description of the
events that would trigger these paymen ts.  Also explain to us why you do not
include a discussion of thes e potential obligations in your financial statements.

Item 9A. Controls and Procedures, page 53
3. Your CEO and CFO concluded that the “d isclosure controls and procedures are
effective in timely alerting them” to info rmation that is required to be disclosed.
Your interim Forms 10-Q contain simila r language.  This conclusion does not
appear to satisfy Item 307 of Regula tion S-K and Rule 13a-15(e) under the
Exchange Act.  Rule 13a-15(e) states th at disclosure controls and procedures
should ensure that information required to  be disclosed “is recorded, processed,
summarized and reported, within the time pe riods specified in the Commission’s
rules and forms.”  Please confirm that th e disclosure controls and procedures
ensure that information required to be disclosed is recorded, processed,
summarized and reported within the time periods specified in the Commission’s
rules and procedures.  If you are una ble to confirm this statement,

• Please provide further explanation incl uding a description of any weaknesses
that prevented the CEO and CFO from conc luding that the disclosure controls
and procedures were effective; and
• Amend the Form 10-K to describe the weaknesses.

Notes to Consolidated Financial Statements, page F-7
 1.  Business and Summary of Signifi cant Accounting Policies, page F-7

 Critical Accounting Policies, page F-7

 Contract Revenue, page F-8

4. Please explain to us why it is appropri ate to recognize a “cumulative impact”
instead of the change on a prospective basi s related to this change in estimate.
Refer to paragraph 19 of SFAS 154.

Steven B. Engle
XOMA Ltd. November 19, 2007 Page 3    3.  Collaborative and Licensing Agreements, page F-17

 Schering Plough, page F-19

5. Please explain to us why you  believe th at it was appropriate to recognize the
maintenance fees in this agreement as well as the Takeda agreement “when they
are due.”  Include a discussion of the natu re, extent and timing of your obligations
under the agreements associated  with these fees.  Refer to the specific paragraphs
within the applicable  authoritative literature upon wh ich you relied in determining
this treatment.

10. Subsequent Events, page F-30
6. Please clarify whether you have any re maining manufacturing obligations under
your agreement with Novartis.  If so, pleas e explain to us why it is appropriate to
recognize the entire $4.3 million in the first quarter of 2007.

Form 10-Q for the quarterly period ended September 30, 2007
 3. Collaborative And Other Arrangements, page 10

Other, page 10
7. We note the disclosure regarding an  August 13, 2007 restated and amended
license agreement with an ex isting technology partner.  Pl ease provide an analysis
supporting your determination that it wa s not necessary to file a Form 8-K
disclosing the amended agreement or file the agreement as an exhibit.

* * * *

 Please provide us the information request ed within 10 busine ss days or tell us
when you will provide us with a response.  Pl ease furnish a cover le tter with your response
that keys your response to our comments.  De tailed cover letters gr eatly facilitate our
review.  Please furnish your letter on EDGAR under the form type label CORRESP.

 We urge all persons who are responsible  for the accuracy and adequacy of the
disclosure in the filings to be certain that  the filings include all information required
under the Securities Exchange Act of 1934 and that they have provided all information
investors require for an informed invest ment decision.  Since the company and its
management are in possession of all facts re lating to a company’s disclosure, they are
responsible for the accuracy and adequacy of the disclosures they have made.

Steven B. Engle
XOMA Ltd. November 19, 2007 Page 4
 In connection with responding to our co mments, please provide, in your letter, a
statement from the company acknowledging that:

• the company is responsible for the adequacy and accuracy of the disclosure in
the filings;
• staff comments or changes to disclosure  in response to staff comments do not
foreclose the Commission from taking a ny action with respect to the filings;
and
• the company may not assert staff comme nts as a defense in any proceeding
initiated by the Commission or any pers on under the federal s ecurities laws of
the United States.

 In addition, please be advi sed that the Division of En forcement has access to all
information you provide to the staff of the Divi sion of Corporation Fi nance in our review
of your filings or in response to our comments on your filings.

Please contact Vanessa Robe rtson, Staff Accountant, at (202) 551-3649 or Jim
Atkinson, Accounting Branch Chief, at (202) 551-3674 if you have any questions
regarding the processing of your response as well as any questions regarding comments
on the financial statements and related matte rs.  You may contact Greg Belliston, Staff
Attorney, at (202) 551-3861 and Suzanne Haye s, Legal Branch Chief, at (202) 551-3675
with questions on any of the ot her comments.  In this regar d, do not hesitate to contact
me, at (202) 551-3679.

        S i n c e r e l y ,

        J i m  B .  R o s e n b e r g
Senior Assistant Chief
Accountant