Exhibit 12.1

CERTIFICATION BY CEO PURSUANT TO SECTION 302

I, Michael Pragnell, certify that:

| | 1. | I have reviewed this annual report on Form 20-F of Syngenta AG;                                                                                                                                                                                                                                                                 
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| | 2. | Based on my knowledge, this annual 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 annual report;        
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| | 3. | Based on my knowledge, the financial statements, and other financial information included in this annual report, fairly present in all material respects the financial condition, results
of operations and cash flows of the company as of, and for, the periods presented in this annual report;                              
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| | 4. | The companys other certifying officer(s) 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) and 15d-15(f)) for the company and have:
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| |    | c)                                                                                                                                                                                                                                                                                                                              
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| |    | d)                                                                                                                                                                                                                                                                                                                              
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| | 5. | The companys other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the companys auditors and
the audit committee of companys board of directors (or persons performing the equivalent functions):                                           
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| |    | b)                                                                                                                                                                                                                                                                                                                              
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Date: February 28, 2006

|       | /s/ Michael Pragnell   
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|       |                        
|Name:  | Michael Pragnell       
|Title: | Chief Executive Officer

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