**Exhibit 31.1**

 

# **Certifications**

 

I,Mark Sieczkarek, certify that:

 

1. Ihave reviewed this report on Form 10-Q of Conceptus, Inc., a Delawarecorporation;

 

2.Based on my knowledge, this quarterly report does not contain any untruestatement of a material fact or omit to state a material fact necessary to makethe statements made, in light of the circumstances under which such statementswere made, not misleading with respect to the period covered by this report;

 

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

 

4. The registrant’s other certifying officer and I are responsible forestablishing and maintaining disclosure controls and procedures (as defined inExchange Act Rules 13a-15(e) and 15d-15(e)) and internal control overfinancial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f)) for the registrant and have:

 

a)              designed such disclosure controls and procedures, orcaused such disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to the registrant,including its consolidated subsidiaries, is made known to us by others withinthose entities, particularly during the period in which this report is beingprepared;

 

b)             designed such internal control over financialreporting, or caused such internal control over financial reporting to bedesigned under our supervision, to provide reasonable assurance regarding thereliability of financial reporting and the preparation of financial statementsfor external purposes in accordance with generally accepted accountingprinciples;

 

c)              evaluated the effectiveness of the registrant’sdisclosure controls and procedures and presented in this report our conclusionabout the effectiveness of the disclosure controls and procedures, as or theend of the period covered by this report based on such evaluation; and

 

d)             disclosed in this report any change in the registrant’sinternal control over financial reporting that occurred during the registrant’smost recent fiscal quarter (the registrant’s fourth fiscal quarter in the caseof an annual report) that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting;and

 

5. Theregistrant’s other certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the registrant’sauditors and the audit committee of registrant’s board of directors (or personsperforming the equivalent functions):

 

a)              all significant deficiencies and material weaknessesin the design or operation of internal control over financial reporting whichare 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 involvesmanagement or other employees who have a significant role in the registrant’sinternal control over financial reporting.

 
| Date: May 10, 2006 |
|-------------------------|
|                    |
|                    | /s/ Mark M. Sieczkarek |   |
|                    | Mark M. Sieczkarek |
|                    | President and Chief Executive Officer |

 

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