**Exhibit 31.1**

 

**CERTIFICATIONS**

 

I, William R. Ringo,certify that:

 

1.                                       Ihave reviewed this quarterly report on Form 10-Q of Abgenix, Inc.;

 

2.                                       Basedon my knowledge, this quarterly report does not contain any untrue statement ofa material fact or omit to state a material fact necessary to make thestatements made, in light of the circumstances under which such statements weremade, not misleading with respect to the period covered by this quarterlyreport;

 

3.                                       Basedon my knowledge, the financial statements, and other financial informationincluded in this quarterly report, fairly present in all material respects thefinancial condition, results of operations and cash flows of the registrant asof, and for, the periods presented in this quarterly report;

 

4.                                       Theregistrant’s other certifying officer and I are responsible for establishingand maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) and internal control over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15d-15(f)) for theregistrant and we have:

 

a) designed suchdisclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that materialinformation relating to the registrant, including its consolidatedsubsidiaries, is made known to us by others within those entities, particularlyduring the period in which this quarterly report is being prepared;

 

b) designed suchinternal control over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles;

 

c) evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this quarterly report our conclusions about the effectiveness ofthe disclosure controls and procedures, as of the end of the period covered bythis quarterly report based on such evaluation; and

 

d) disclosed in thisquarterly report any change in the registrant’s internal control over financialreporting that occurred during the registrant’s most recent fiscal quarter (theregistrant’s fourth fiscal quarter in the case of an annual report) that hasmaterially affected, or is reasonably likely to materially affect, theregistrant’s internal control over financial reporting; and

 

5.                                       Theregistrant’s other certifying officer and I have disclosed, based on our mostrecent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of registrant’s board ofdirectors (or persons performing the equivalent functions):

 

a) all significantdeficiencies and material weaknesses in the design or operation of internalcontrol over financial reporting which are reasonably likely to adverselyaffect the registrant’s ability to record, process, summarize and reportfinancial information; and

 

b) any fraud, whether ornot material, that involves management or other employees who have asignificant role in the registrant’s internal control over financial reporting.

 

 

Dated: May 10, 2005

 

 
|   |   | /s/   WILLIAM R. RINGO |   |
|--------|--------|---------------------------------------|--------|
|   |   | William R. Ringo                      |
|   |   | President and Chief Executive Officer |
|   |   | (Principal Executive Officer)         |

 

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