**Exhibit 12.1**

CERTIFICATIONS 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;                                                                                                                                                                                                                                                                                          |
|--------|----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |     |                                                                                                                                                                                                                                                                                                                                                        |
|   | 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; |
|   |     |                                                                                                                                                                                                                                                                                                                                                        |
|   | 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 company as of, and    for, the periods presented in this report;                                                |
|   |     |                                                                                                                                                                                                                                                                                                                                                        |
|   | 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)) for the company and 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 company, 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)     | [Paragraph omitted pursuant    to SEC Release Nos. 33-8238 and 34-47986]                                                                                                                                                                                                                                                                                                                                   |
|   |   |   |                                                                                                                                                                                                                                                                                                                                                                                                       |
|   |   | c)     | Evaluated the effectiveness        of the company’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 company’s internal control over financial reporting        that occurred during the period covered by the annual report that has materially        affected, or is reasonably likely to materially affect, the company’s    internal control over financial reporting; and                                                                     |

|   |           |                                                                                                                                                                                                                                                                                                               |
|--------|----------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   | 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): |
|   |           |                                                                                                                                                                                                                                                                                                               |

|   |   | a)     | All significant        deficiencies and material weaknesses in the design or operation of internal        controls over financial reporting which are reasonably likely to adversely        affect the company’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 company's internal controls over financial reporting.                                                                                                                   |

Date: March 24, 2004

 

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

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