----

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| x ANNUAL REPORT PURSUANT TO SECTION 13 or 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| For the fiscal year ended December 31, 2010                                                                                                                                   |
| OR                                                                                                                                                                            |
| o   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934                                                              |
| for the transition period from                          to |

| Bermuda                                                        | 52-2154066                                      |
|----------------------------------------------------------------|-------------------------------------------------|
| (State or other jurisdiction of incorporation or organization) | (I.R.S.  Employer Identification No.) |
|                                                           |                                            |
| 2910 Seventh Street, Berkeley, California 94710                | (510) 204-7200                                  |
| (Address of principal executive offices, including zip code)   | (Telephone Number)                              |

| Title of each class                                                   | Name of each exchange on which registered |
|-----------------------------------------------------------------------|-------------------------------------------|
| Common Shares, U.S. $0.0075 par valuePreference Share Purchase Rights | The NASDAQ Global Market                  |

----

----

----

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| XOMA LTD.  By:   /s/ Steven B. Engle        Steven B. Engle        Chairman of the Board, Chief Executive Officer         and President |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|          Signature | Title                                                                                                              | Date               |
|-----------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------|--------------------|
|                                                            |                                                                                                               |               |
| /s/ Steven B. Engle(Steven B. Engle)                            | Chairman of the Board, Chief Executive Officer and President (Principal Executive Officer)                         | May 26, 2011       |
|                                                            |                                                                                                               |               |
| /s/ Fred Kurland(Fred Kurland)                                  | Vice President, Finance and Chief Financial Officer (Principal Financial Officer and Principal Accounting Officer) |  May 26, 2011 |
|                                                            |                                                                                                               |               |
| /s/ Patrick J. Scannon(Patrick J. Scannon, M.D., Ph.D.)         | Executive Vice President and Chief Scientific Officer and Director                                                 | May 26, 2011       |
|                                                            |                                                                                                               |               |
| /s/ W. Denman Van Ness(W. Denman Van Ness)                      | Lead Independent Director                                                                                          | May 26, 2011       |
|                                                            |                                                                                                               |               |
| /s/ William K. Bowes, Jr.(William K. Bowes, Jr.)                | Director                                                                                                           | May 26, 2011       |
|                                                            |                                                                                                               |               |
| /s/ Peter Barton Hutt(Peter Barton Hutt)                        | Director                                                                                                           | May 26, 2011       |
|                                                            |                                                                                                               |               |
| /s/ John Varian(John Varian)                                    | Director                                                                                                           | May 26, 2011       |
|                                                            |                                                                                                               |               |
| /s/ Timothy P. Walbert(Timothy P. Walbert)                      | Director                                                                                                           | May 26, 2011       |
|                                                            |                                                                                                               |               |
| /s/ Jack L. Wyszomierski(Jack L. Wyszomierski)                  | Director                                                                                                           | May 26, 2011       |

----

|                         |                                                                                                                                                                                                          |   |
|------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|
| ExhibitNumber                |                                                                                                                                                                                                     |   |   |
|   1.1    |   Underwriting Agreement dated February 2, 2010 (Exhibit 10.1)1                                                                                                                                     |   |
|                         |                                                                                                                                                                                                          |   |
|   3.1    |   Memorandum of Continuance of XOMA Ltd. (Exhibit 3.4)2                                                                                                                                             |   |
|                         |                                                                                                                                                                                                          |   |
|   3.2    |   Bye-Laws of XOMA Ltd. (as amended) (Exhibit 3.2)3                                                                                                                                                 |   |
|                         |                                                                                                                                                                                                          |   |
|   4.1    |   Shareholder Rights Agreement dated as of February 26, 2003 by and between XOMA Ltd. and Mellon Investor Services LLC as Rights Agent (Exhibit 4.1)3                                               |   |
|                         |                                                                                                                                                                                                          |   |
|   4.1A   |   Amendment to Shareholder Rights Agreement dated December 21, 2010 between XOMA Ltd. and Wells Fargo Bank, N.A. as Rights Agent**                                                                  |   |
|                         |                                                                                                                                                                                                          |   |
|   4.2    |   Resolution Regarding Preferences and Rights of Series A Preference Shares (Exhibit A to Exhibit 4.1)3                                                                                             |   |
|                         |                                                                                                                                                                                                          |   |
|   4.3    |   Resolution Regarding Preferences and Rights of Series B Preference Shares (Exhibit B to Exhibit 3)4                                                                                               |   |
|                         |                                                                                                                                                                                                          |   |
|   4.4    |   Indenture between XOMA Ltd. and Wells Fargo Bank, National Association, as trustee, relating to the Company’s 6.50% Convertible SNAPs SM due February 1, 2012   (Exhibit 2)5 |   |
|                         |                                                                                                                                                                                                          |   |
|   4.5    |   Form of Warrant (May 2009 Warrants) (Exhibit 10.2)6                                                                                                                                               |   |
|                         |                                                                                                                                                                                                          |   |
|   4.5A   |   Form of Amended and Restated Warrant (May 2009 Warrants) (Exhibit 10.5)1                                                                                                                          |   |
|                         |                                                                                                                                                                                                          |   |
|   4.6    |   Form of Warrant (June 2009 Warrants) (Exhibit 10.2)7                                                                                                                                              |   |
|                         |                                                                                                                                                                                                          |   |
|   4.6A             |   Form of Amended and Restated Warrant (June 2009 Warrants) (Exhibit 10.6)1                                                                                                                         |   |
|                         |                                                                                                                                                                                                          |   |
|   4.7    |   Form of Warrant (February 2010 Warrants) (Exhibit 10.2)1                                                                                                                                          |   |
|                         |                                                                                                                                                                                                          |   |
| 10.1               |   1981 Share Option Plan as amended and restated (Exhibit 10.1)8                                                                                                                                    |   |
|                         |                                                                                                                                                                                                          |   |
| 10.1A                        |   Form of Share Option Agreement for 1981 Share Option Plan (Exhibit 10.1A)9                                                                                                                        |   |
|                         |                                                                                                                                                                                                          |   |
| 10.2               |   Restricted Share Plan as amended and restated (Exhibit 10.2)8                                                                                                                                     |   |
|                         |                                                                                                                                                                                                          |   |
| 10.2A                        |   Form of Share Option Agreement for Restricted Share Plan (Exhibit 10.2A)9                                                                                                                         |   |
|                         |                                                                                                                                                                                                          |   |
| 10.3                         |   2007 CEO Share Option Plan (Exhibit 10.7)10                                                                                                                                                       |   |
|                         |                                                                                                                                                                                                          |   |
| 10.4               |   1992 Directors Share Option Plan as amended and restated (Exhibit 10.3)8                                                                                                                          |   |
|                         |                                                                                                                                                                                                          |   |
| 10.4A                        |   Form of Share Option Agreement for 1992 Directors Share Option Plan (initial grants) (Exhibit 10.3A)9                                                                                             |   |
|                         |                                                                                                                                                                                                          |   |
| 10.4B                        |   Form of Share Option Agreement for 1992 Directors Share Option Plan (subsequent grants) (Exhibit 10.3B)9                                                                                          |   |
|                         |                                                                                                                                                                                                          |   |
| 10.5                         |   2002 Director Share Option Plan (Exhibit 10.10)11                                                                                                                                                 |   |
|                         |                                                                                                                                                                                                          |   |
| 10.6               |   2010 Long Term Incentive and Share Award Plan (Exhibit 10.5)8                                                                                                                                     |   |
|                         |                                                                                                                                                                                                          |   |
| 10.6A              |   Form of Share Option Agreement for 2010 Long Term Incentive and Share Award Plan (Exhibit 10.5A)8                                                                                                 |   |
|                         |                                                                                                                                                                                                          |   |
| 10.7               |   Management Incentive Compensation Plan as amended and restated (Exhibit 10.3)12                                                                                                                   |   |
|                         |                                                                                                                                                                                                          |   |
| 10.7A                        |   CEO Incentive Compensation Plan (Exhibit 10.4A)9                                                                                                                                                  |   |
|                         |                                                                                                                                                                                                          |   |
| 10.7B                        |   Bonus Compensation Plan (Exhibit 10.4B)9                                                                                                                                                          |   |
|                         |                                                                                                                                                                                                          |   |
| 10.8               |   1998 Employee Share Purchase Plan as amended and restated (Exhibit 10.4)8                                                                                                                         |   |
|                         |                                                                                                                                                                                                          |   |
| 10.9               |   Form of Amended and Restated Indemnification Agreement for Officers (Exhibit 10.6)13                                                                                                              |   |
|                         |                                                                                                                                                                                                          |   |

----

| 10.9A                         |   Form of Amended and Restated Indemnification Agreement for Employee Directors (Exhibit 10.7)13                                                                                                                                                                                                                                                                             |
|-------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.9B                         |   Form of Amended and Restated Indemnification Agreement for Non-employee Directors (Exhibit 10.8)13                                                                                                                                                                                                                                                                         |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.10               |   Amended and Restated Employment Agreement entered into between XOMA (US) LLC and Steven B. Engle, dated as of December 30, 2008 (Exhibit 10.7)14                                                                                                                                                                                                                           |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.10A              |   Amended and Restated Employment Agreement entered into between XOMA (US) LLC and Patrick J. Scannon, dated as of December 30, 2008 (Exhibit 10.7A)14                                                                                                                                                                                                                       |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.10B              |   Amended and Restated Employment Agreement entered into between XOMA (US) LLC and Fred Kurland, dated as of December 29, 2008 (Exhibit 10.7B)14                                                                                                                                                                                                                             |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.10C              |   Amended and Restated Employment Agreement entered into between XOMA (US) LLC and Christopher J. Margolin, dated as of December 30, 2008 (Exhibit 10.7C)14                                                                                                                                                                                                                  |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.10D              |   Amended and Restated Employment Agreement entered into between XOMA (US) LLC and Charles C. Wells, dated as of December 30, 2008 (Exhibit 10.7D)14                                                                                                                                                                                                                         |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.11                         |   Consulting Agreement effective as of August 3, 2007 between XOMA (US) LLC and John L. Castello (Exhibit 10.8)10                                                                                                                                                                                                                                                            |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.12     |   Form of Change of Control Severance Agreement entered into between XOMA Ltd. and certain of its executives, with reference schedule **                                                                                                                                                                                                                                     |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.13     |   Lease of premises at 890 Heinz Street, Berkeley, California dated as of July 22, 1987 (Exhibit 10.12)15                                                                                                                                                                                                                                                               |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.14                         |   Lease of premises at Building E at Aquatic Park Center, Berkeley, California dated as of July 22, 1987 and amendment thereto dated as of April 21, 1988 (Exhibit 10.13)15                                                                                                                                                                                                  |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.15                         |   Lease of premises at Building C at Aquatic Park Center, Berkeley, California dated as of July 22, 1987 and amendment thereto dated as of August 26, 1987 (Exhibit 10.14)15                                                                                                                                                                                                 |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.16                         |   Letter of Agreement regarding CPI adjustment dates for leases of premises at Buildings C, E and F at Aquatic Park Center, Berkeley, California dated as of July 22, 1987   (Exhibit 10.15)15                                                                                                                                                                     |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.17                         |   Lease of premises at 2910 Seventh Street, Berkeley, California dated March 25, 1992 (Exhibit 10.16)15                                                                                                                                                                                                                                                                 |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.17A                        |   Fifth amendment to lease of premises at 2910 Seventh Street, Berkeley, California dated June 1, 2006 (Exhibit 10.58)16                                                                                                                                                                                                                                                     |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.18               |   Lease of premises at 5860 and 5864 Hollis Street, Emeryville, California dated as of November 2, 2001 (with addendum) (Exhibit 10.19)17                                                                                                                                                                                                                                    |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.19               |   Lease of premises at 2850 Seventh Street, Second Floor, Berkeley, California dated as of December 28, 2001 (with addendum and guaranty) (Exhibit 10.20)17                                                                                                                                                                                                                  |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.20               |   Amended and Restated Research and License Agreement dated September 1, 1993, between the Company and New York University (with certain confidential information   omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit   10.28)15 |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.20A                        |   Third Amendment to License Agreement dated June 12, 1997, between the Company and New York University (with certain confidential information omitted, which   omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.28A)15                               |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.20B                        |   Fourth Amendment to License Agreement dated December 23, 1998, between the Company and New York University (Exhibit 10.22B)18                                                                                                                                                                                                                                              |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.20C                        |   Fifth Amendment to License Agreement dated June 25, 1999, between the Company and New York University (with certain confidential information omitted, which   omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.21C)19                               |
|                          |                                                                                                                                                                                                                                                                                                                                                                                   |

----

| 10.20D             |   Sixth Amendment to License Agreement dated January 25, 2000, between the Company and New York University (with certain confidential information omitted, which   omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.1)20                                                                                                  |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.20E             |   Seventh Amendment to License Agreement by and among New York University, XOMA Technology Limited and XOMA Ireland Limited effective as of November 10,   2004 (with certain confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the   Securities and Exchange Commission) (Exhibit 3)21                                           |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.21    |   Second Amended and Restated Collaboration Agreement dated January 12, 2005, by and between XOMA (US) LLC and Genentech, Inc. (with certain confidential   information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange   Commission (Exhibit 10.26C)22                                                                      |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.21A             |   Agreement related to LUCENTIS ® License Agreement and RAPTIVA ® Collaboration Agreement dated September 9, 2009, by and between XOMA (Bermuda) Ltd.,   XOMA (US) LLC and Genentech, Inc. (with certain confidential information omitted, which omitted information is the subject of a confidential treatment request and has   been filed separately with the Securities and Exchange Commission) (Exhibit 10.18A)23 |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.22    |   License Agreement by and between XOMA Ireland Limited and MorphoSys AG, dated as of February 1, 2002 (with certain confidential information omitted, which   omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.43)24                                                                                                          |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.23    |   Amended and Restated License Agreement by and between XOMA Ireland Limited and DYAX Corp., dated as of October 27, 2006 (with certain confidential information   omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit    10.32)13                                                                          |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.24    |   License Agreement by and between XOMA Ireland Limited and Cambridge Antibody Technology Limited, dated as of December 22, 2002 (with certain confidential    information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange    Commission) (Exhibit 10.46)3                                                                   |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.25    |   License Agreement, dated as of December 29, 2003, by and between Diversa Corporation and XOMA Ireland Limited (with certain confidential information omitted, which    omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 2)25                                                                                                    |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.25A   |   GSSM License Agreement, effective as of May 2, 2008, by and between Verenium Corporation and XOMA Ireland Limited (with certain confidential information omitted,   which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission)**                                                                                                             |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.26    |   Agreement, dated February 27, 2004, by and between Chiron Corporation and XOMA (US) LLC (with certain confidential information omitted, which omitted information   is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.50)26                                                                                                                       |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.26A             |   Research, Development and Commercialization Agreement, dated as of May 26, 2005, by and between Chiron Corporation and XOMA (US) LLC (with certain confidential   information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange   Commission) (Exhibit 10.2)27                                                               |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 10.26B             |   Secured Note Agreement, dated as of May 26, 2005, by and between Chiron Corporation and XOMA (US) LLC (with certain confidential information omitted, which   omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.3)27                                                                                                          |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |

----

| 10.26C            |   Amended and Restated Agreement Research, Development and Commercialization Agreement, executed November 7, 2008, by and between Novartis Vaccines and   Diagnostics, Inc. (formerly Chiron Corporation) and XOMA (US) LLC (with certain confidential information omitted, which omitted information is the subject of a   confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.24C)28 |
|-------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.26D            |   Manufacturing and Technology Transfer Agreement, executed December 16, 2008, by and between Novartis Vaccines and Diagnostics, Inc. (formerly Chiron Corporation)   and XOMA (US) LLC (with certain confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed   separately with the Securities and Exchange Commission) (Exhibit 10.24D)28                                     |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.27   |   Collaboration Agreement, dated as of September 23, 2004, by and between Aphton Corporation and XOMA (US) LLC (with certain confidential information omitted,    which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 2)29                                                                                                                       |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.28   |   Agreement dated March 8, 2005, between XOMA (US) LLC and the National Institute of Allergy and Infectious Diseases (with certain confidential information omitted,    which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.53)22                                                                                                                  |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.28A            |   Agreement dated July 28, 2006, between XOMA (US) LLC and the National Institute of Allergy and Infectious Diseases (Exhibit 10.60)16                                                                                                                                                                                                                                                                                                                                       |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.28B            |   Agreement dated September 15, 2008, between XOMA (US) LLC and the National Institute of Allergy and Infectious Diseases (with certain confidential information    omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit    10.39)30                                                                                                |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.28C            |   Second Amendment to Agreement dated September 15, 2008, between XOMA (US) LLC and the National Institute of Allergy and Infectious Diseases (Exhibit 10.24C)31                                                                                                                                                                                                                                                                                                             |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.29   |   License Agreement, effective as of June 20, 2005, by and between Merck & Co., Inc. and XOMA Ireland Limited (with certain confidential information omitted, which    omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 10.4)27                                                                                                                      |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.30   |   Form of Dealer Manager Agreement relating to the Company’s 6.50% Convertible SNAPs SM due February 1, 2012 (Exhibit 1.1)32                                                                                                                                                                                                                                                                                                                                      |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.30A            |   Form of Placement Agreement relating to the Company’s 6.50% Convertible SNAPs SM due February 1, 2012 (Exhibit 1.2)32                                                                                                                                                                                                                                                                                                                                           |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.31   |   Collaboration Agreement dated as of May 22, 2006, by and between Schering Corporation, acting through its Schering-Plough Research Institute division, and XOMA    (US) LLC (with certain confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the   Securities and Exchange Commission) (Exhibit 10.59)16                                                |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.32   |   Collaboration Agreement, dated as of November 1, 2006, between Takeda Pharmaceutical Company Limited and XOMA (US) LLC (with certain confidential information   omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit   10.46)13                                                                                              |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.32A            |   First Amendment to Collaboration Agreement, effective as of February 28, 2007, between Takeda Pharmaceutical Company Limited and XOMA (US) LLC (with certain   confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and   Exchange Commission) (Exhibit 10.48)33                                                                           |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 10.32B            |   Second Amendment to Collaboration Agreement, effective as of February 9, 2009, among Takeda Pharmaceutical Company Limited and XOMA (US) LLC (with certain   confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and   Exchange Commission) (Exhibit 10.31B)28                                                                            |
|              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |

----

| 10.33    |   Loan Agreement, dated as of November 9, 2006, between Goldman Sachs Specialty Lending Holdings, Inc., XOMA (US) LLC and XOMA Ltd. (with certain confidential   information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange   Commission) (Exhibit 10.47)13                         |
|--------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.33A             |   Amended & Restated Loan Agreement, dated as of May 9, 2008 between Goldman Sachs Specialty Lending Holdings, Inc., XOMA Ltd. and XOMA (US) LLC (with    certain confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and    Exchange Commission) (Exhibit 10.37)34      |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.34    |   License Agreement, effective as of August 27, 2007, by and between Pfizer Inc. and XOMA Ireland Limited (with certain confidential information omitted, which omitted    information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission) (Exhibit 2)35                                                             |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.35    |   Common Stock Purchase Agreement, dated as of October 21, 2008, by and between XOMA Ltd. and Azimuth Opportunity Ltd. (Exhibit 10.1)36                                                                                                                                                                                                                                                                  |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.35A   |   Common Stock Purchase Agreement, dated as of July 23, 2010, by and between XOMA Ltd. and Azimuth Opportunity Ltd. (Exhibit 10.1) 37                                                                                                                                                                                                                                                                         |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.36    |   Securities Purchase Agreement dated May 15, 2009, between XOMA Ltd. and the investors named therein (Exhibit 10.1)6                                                                                                                                                                                                                                                                                         |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.36A             |   Engagement Letter dated May 15, 2009 (Exhibit 10.3)6                                                                                                                                                                                                                                                                                                                                                        |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.36B   |   Securities Purchase Agreement dated June 5, 2009, between XOMA Ltd. and the investors named therein (Exhibit 10.1)7                                                                                                                                                                                                                                                                                         |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.36C             |   Engagement Letter dated June 4, 2009 (Exhibit 10.3)7                                                                                                                                                                                                                                                                                                                                                        |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.37    |   Discovery Collaboration Agreement dated September 9, 2009, by and between XOMA Development Corporation and Arana Therapeutics Limited (with certain   confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and   Exchange Commission) (Exhibit 10.35)38                     |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.38    |   At Market Issuance Sales Agreement dated July 14, 2009, between XOMA Ltd. and Wm Smith & Co. (Exhibit 10.36)23                                                                                                                                                                                                                                                                                          |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.38A   |   At Market Issuance Sales Agreement dated October 26, 2010, between XOMA Ltd. and Wm Smith & Co. and McNicholl, Lewis & Vlak LLC (Exhibit 10.1)39                                                                                                                                                                                                                                                    |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.38B   |   At Market Issuance Sales Agreement dated February 4, 2011, between XOMA Ltd. and McNicholl, Lewis & Vlak LLC (Exhibit 1.2)40                                                                                                                                                                                                                                                                            |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.39    |   Discovery Collaboration Agreement dated October 29, 2009, by and between XOMA Development Corporation and The Chemo-Sero-Therapeutic Research Institute   (with certain confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities    and Exchange Commission) (Exhibit 10.36) 41 |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.40    |   Warrant Amendment Agreement dated February 2, 2010 (May 2009 Warrants) (Exhibit 10.3)1                                                                                                                                                                                                                                                                                                                      |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.40A             |   Form of Warrant Amendment Agreement dated February 2, 2010 (June 2009 Warrants) (Exhibit 10.4)1                                                                                                                                                                                                                                                                                                             |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 10.41    |   Royalty Purchase Agreement, dated as of August 12, 2010, by and among XOMA CDRA LCC, XOMA (US) LLC, XOMA Ltd. and the buyer named therein (with certain    confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and   Exchange Commission) (Exhibit 10.38)31                |
|               |                                                                                                                                                                                                                                                                                                                                                                                                                    |

----

| 10.42              |   Collaboration and License Agreement dated as of December 30, 2010, by and between XOMA Ireland Limited, Les Laboratoires Servier and Institut de Recherches Servier    (with certain confidential information omitted, which omitted information is the subject of a confidential treatment request and has been filed separately with the Securities    and Exchange Commission)** |
|------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 10.42A             |   Loan Agreement dated as of December 30, 2010, by and between XOMA Ireland Limited and Les Laboratoires Servier (with certain confidential information omitted, which    omitted information is the subject of a confidential treatment request and has been filed separately with the Securities and Exchange Commission)*                                                                    |
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 21.1     |   Subsidiaries of the Company**                                                                                                                                                                                                                                                                                                                                                                           |
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 23.1     |   Consent of Independent Registered Public Accounting Firm**                                                                                                                                                                                                                                                                                                                                              |
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 31.1     |   Certification of Steven B. Engle, filed pursuant to Section 302 of the Sarbanes-Oxley Act of 2002*                                                                                                                                                                                                                                                                                                      |
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 31.2     |   Certification of Fred Kurland, filed pursuant to Section 302 of the Sarbanes-Oxley Act of 2002*                                                                                                                                                                                                                                                                                                         |
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 32.1     |   Certification of Steven B. Engle, furnished pursuant to Section 906 of the Sarbanes-Oxley Act of 2002*                                                                                                                                                                                                                                                                                                  |
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 32.2     |   Certification of Fred Kurland, furnished pursuant to Section 906 of the Sarbanes-Oxley Act of 2002*                                                                                                                                                                                                                                                                                                     |
|                         |                                                                                                                                                                                                                                                                                                                                                                                                                |
| 99.1     |   Press Release dated March 10, 2010 previously furnished with the Form 10-K on March 10, 2011                                                                                                                                                                                                                                                                                                            |

| ** | Previously filed with the Form 10-K on March 10, 2011.                                                                                                                       |
|----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| *  | Filed herewith.                                                                                                                                                              |
| 1  | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed February 2, 2010.                                                |
| 2  | Incorporated by reference to the referenced exhibit to the Company’s Registration Statement on Form S-4 filed November 27, 1998, as amended.                      |
| 3  | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2002.                      |
| 4  | Incorporated by reference to the referenced exhibit to the Company’s Amendment No. 1 to Form 8-K/A filed April 18, 2003.                                     |
| 5  | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed February 13, 2006.                                          |
| 6  | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed May 19, 2009.                                                    |
| 7  | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed June 10, 2009.                                                   |
| 8  | Incorporated by reference to the referenced exhibit to the Company’s Registration Statement on Form S-8 (File No. 333-171429) filed December 27, 2010.                 |
| 9  | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2007, as amended.          |
| 10 | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed August 7, 2007.                                                  |
| 11 | Incorporated by reference to the referenced exhibit to the Company’s Registration Statement on Form S-8 (File No. 333-151416) filed June 4, 2008.                      |
| 12 | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed November 6, 2007.                                                |
| 13 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2006.                      |
| 14 | Incorporated by reference to the referenced exhibit to the Company’s Amendment No. 2 to Annual Report on Form 10-K/A for the fiscal year ended December 31, 2009. |
| 15 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 1997, as amended.          |

----

| 16 | Incorporated by reference to the referenced exhibit to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2006.                                                          |
|----|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 17 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2001.                                                              |
| 18 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 1998.                                                              |
| 19 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 1999.                                                              |
| 20 | Incorporated by reference to the referenced exhibit to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2000.                                                         |
| 21 | Incorporated by reference to the referenced exhibit to the Company’s Amendment No. 1 on Form 8-K/A filed November 30, 2004.                                                                          |
| 22 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2004.                                                              |
| 23 | Incorporated by reference to the referenced exhibit to the Company’s Quarterly Report on Form 10-Q filed November 9, 2009.                                                                                     |
| 24 | Incorporated by reference to the referenced exhibit to Amendment No. 2 to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2002 filed on December 12, 2002. |
| 25 | Incorporated by reference to the referenced exhibit to the Company’s Amendment No. 2 on Form 8-K/A filed March 19, 2004.                                                                             |
| 26 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2003.                                                              |
| 27 | Incorporated by reference to the referenced exhibit to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2005.                                                          |
| 28 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2008.                                                              |
| 29 | Incorporated by reference to the referenced exhibit to the Company’s Amendment No. 1 on Form 8-K/A filed October 26, 2004.                                                                                |
| 30 | Incorporated by reference to the referenced exhibit to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2008.                                                          |
| 31 | Incorporated by reference to the referenced exhibit to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2010 filed on November 4, 2010.                                |
| 32 | Incorporated by reference to the referenced exhibit to Amendment No. 2 to the Company’s Registration Statement on Form S-4 filed January 11, 2006.                                                        |
| 33 | Incorporated by reference to the referenced exhibit to Amendment No. 1 to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2007 filed on March 5, 2010.                    |
| 34 | Incorporated by reference to the referenced exhibit to Amendment No. 2 to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2008 filed on March 5, 2010.                     |
| 35 | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed September 13, 2007.                                                                                      |
| 36 | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed October 22, 2008.                                                                                   |
| 37 | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed July 23, 2010.                                                                                           |
| 38 | Incorporated by reference to the referenced exhibit to Amendment No. 1 to the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2009 filed on March 5, 2010.                |
| 39 | Incorporated by reference to the referenced exhibit to the Company’s Current Report on Form 8-K filed October 26, 2010.                                                                                        |
| 40 | Incorporated by reference to the referenced exhibit to the Company’s Registration Statement on Form S-3 (File No. 333-172197) filed February 11, 2011.                                                         |
| 41 | Incorporated by reference to the referenced exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2009.                                                              |

----

| 1. | I have reviewed this annual report on Form 10-K/A of XOMA Ltd.; |
|----|-----------------------------------------------------------------|

| 2. | Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report; |
|----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| 3. | Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report; |
|----|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| 4. | The registrant’s other certifying officers and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f))) for the registrant and we have: |
|----|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (a)   | Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared; |
|-----------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (b)   | Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles; |
|-----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (c)   | Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and |
|-----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (d)   | Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and |
|-----------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| 5. | The registrant’s other certifying officers and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of registrant’s board of directors (or persons performing the equivalent function): |
|----|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (a)   | All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and |
|-----------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (b)   | Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting. |
|-----------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| Date:  May 26, 2011 |   | /s/ STEVEN B. ENGLESteven B. EngleChairman, Chief Executive Officer and President |
|-------------------------------|--------|-----------------------------------------------------------------------------------|

----

| 2. | Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report; |
|----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| 3. | Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report; |
|----|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| 4. | The registrant’s other certifying officers and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f))) for the registrant and we have: |
|----|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (a)   | Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared; |
|-----------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (b)   | Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles; |
|-----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (c)   | Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and |
|-----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (d)   | Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and |
|-----------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| 5. | The registrant’s other certifying officers and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of registrant’s board of directors (or persons performing the equivalent function): |
|----|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (a)   | All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and |
|-----------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (b)   | Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting. |
|-----------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| Date:  May 26, 2011 |   | /s/ FRED KURLAND Fred KurlandVice President, Finance and Chief Financial Officer |
|-------------------------------|--------|---------------------------------------------------------------------------------------|

----

| Date:  May 26, 2011 |   | /s/ STEVEN B. ENGLESteven B.  EngleChairman, Chief Executive Officer and President |
|-------------------------------|--------|----------------------------------------------------------------------------------------------|

----

| Date:  May 26, 2011 |   | /s/ FRED KURLANDFred KurlandVice President, Finance and Chief Financial Officer |
|-------------------------------|--------|---------------------------------------------------------------------------------|