**Exhibit 23.1**

 

**CONSENT OF INDEPENDENT REGISTEREDPUBLIC ACCOUNTING FIRM**

 

Weconsent to the incorporation by reference in the following RegistrationStatements:

 
| (1)    | Registration Statement  (Form S-8 Nos. 33-20181, 33-35182, 2-90595) pertaining to the Chiron Corporation  1982 Stock Option Plan                                     |
|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                                                                                                      |
| (2)    | Registration Statement  (Form S-8 Nos. 33-23899 and 33-58305) pertaining to the Chiron  Corporation 1988 Employee Stock Purchase Plan                                |
|   |                                                                                                                                                                      |
| (3)    | Registration Statement  (Form S-8 Nos. 33-44477, 33-65024, 33-65177, 333-10419, 333-28257,  333-81794) pertaining to the Chiron Corporation 1991 Stock Option Plan   |
|   |                                                                                                                                                                      |
| (4)    | Registration Statement  (Form S-8 No. 33-45822) pertaining to the Chiron Corporation 1986  Incentive Stock Option Plan of IntraOptics, Inc.                |
|   |                                                                                                                                                                      |
| (5)    | Registration Statement  (Form S-8 No. 33-63297) pertaining to the Chiron Corporation 1989  Stock Option Plan of Viagene, Inc.                              |
|   |                                                                                                                                                                      |
| (6)    | Registration Statement  (Form S-8 No. 333-42469) pertaining to the Chiron Corporation  Supplemental Executive Retirement Plan                                   |
|   |                                                                                                                                                                      |
| (7)    | Registration Statement  (Form S-8 No. 333-49229) pertaining to the Chiron Corporation 1997  Employee Stock Purchase Plan                                        |
|   |                                                                                                                                                                      |
| (8)    | Registration Statement  (Form S-8 No. 333-121126) pertaining to the Chiron Corporation  Supplemental Retirement Plan and Supplemental Executive Retirement Plan |
|   |                                                                                                                                                                      |
| (9)    | Registration Statement  (Form S-8 No. 333-118038) pertaining to the Chiron Corporation 2004  Stock Compensation Plan                                            |
|   |                                                                                                                                                                      |
| (10)   | Registration Statement  (Form S-3/S-4 No. 33-43574) of Chiron Corporation                                                                                       |
|   |                                                                                                                                                                      |
| (11)   | Registration Statement  (Form S-3 No. 333-109045) of Chiron Corporation                                                                                         |
|   |                                                                                                                                                                      |
| (12)   | Registration Statement  (Form S-3 No. 333-67860) of Chiron Corporation                                                                                          |
|   |                                                                                                                                                                      |
| (13)   | Registration Statement  (Form S-3 No. 333-118948) of Chiron Corporation                                                                                         |

 

of our report dated March14, 2006 (except for Note 20, as to which the date is March 16, 2006), withrespect to the consolidated financial statements and schedule of ChironCorporation, and our report dated March 14, 2006 with respect to ChironCorporation management’s assessment of the effectiveness of internal controlover financial reporting, and the effectiveness of internal control overfinancial reporting of Chiron Corporation, included in this Annual Report(Form 10-K) for the year ended December 31, 2005.

 

 
|   |   | /s/ Ernst & Young LLP |
|--------|--------|---------------------------|

 

 

Palo Alto,California

March 16, 2006

 

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