**Exhibit 31.1**

**CERTIFICATIONOF CHIEF EXECUTIVE OFFICERAS ADOPTED PURSUANT TOSECTION 302 OF THE SARBANES-OXLEY ACT OF 2002**

I,James T. Demetriades, certify that:

1.      I have reviewed this Annual Report on Form 10-K for theyear ended December 31, 2004 of SeeBeyond Technology Corporation;

2.      Based on my knowledge, this 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 statements weremade, not misleading with respect to the period covered by this report;

3.      Based on my knowledge, the financial statements, and otherfinancial information included in this report, fairly present in all materialrespects the financial condition, results of operations and cash flows of theregistrant as of, and for, the periods presented in this report;

4.      The registrant’s other certifying officer(s) and I areresponsible for establishing and maintaining disclosure controls and procedures(as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) andinternal control over financial 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, or caused suchdisclosure controls and procedures to be designed under our supervision, toensure that material information relating to the registrant, including itsconsolidated subsidiaries, is made known to us by others within those entities,particularly during the period in which this report is being prepared;

(b)   Designed such internal control over financial reporting, or causedsuch internal control over financial reporting to be designed under oursupervision, to provide reasonable assurance regarding the reliability of financialreporting and the preparation of financial statements for external purposes inaccordance with generally accepted accounting principles;

(c)    Evaluated the effectiveness of the registrant’s disclosurecontrols and procedures and presented in this report our conclusions about theeffectiveness of the disclosure controls and procedures, as of the end of theperiod covered by this report based on such evaluation; and

(d)   Disclosed in this report any change in the registrant’s internalcontrol over financial reporting that occurred during the registrant’s mostrecent fiscal quarter (the registrant’s fourth fiscal quarter in the case of anannual report) that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting;and

5.      The registrant’s other certifying officer(s) and I havedisclosed, based on our most recent evaluation of internal control overfinancial reporting, to the registrant’s auditors and the audit committee ofthe registrant’s board of directors (or persons performing the equivalentfunctions):

(a)    All significant deficiencies and material weaknesses in thedesign or operation of internal control over financial reporting which arereasonably 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 involves management orother employees who have a significant role in the registrant’s internalcontrol over financial reporting.
| Date: March 9,  2005 | By:    | /s/  *JAMES T. DEMETRIADES* |
|---------------------------|--------|-----------------------------|
|                      | Name:  | James  T. Demetriades       |
|                      | Title: | *Chief Executive Officer*   |

 

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