**Exhibit 31.1**

 

**CERTIFICATION OF CHIEF EXECUTIVE OFFICER**

**PURSUANT TO RULE 13a-14(a) AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002**

 

I,Ray J. Oleson, certifythat:

 

1.     I have reviewed thisquarterly report on Form 10-Q of SI International, Inc.;

 

2.     Based on my knowledge, thisreport does not contain any untrue statement of a material fact or omit tostate a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading withrespect to the period covered by this report;

 

3.     Based on my knowledge, thefinancial statements, and other financial information included in this report,fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periodspresented in this report;

 

4.     The registrant’s othercertifying officer(s) and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e)and 15d-15(e)) 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)    [Omitted pursuant to “Management’s Reports on Internal ControlOver Financial Reporting and Certification of Disclosure in Exchange ActPeriodic Reports,” SEC Release No. 33-8238 (June 5, 2003)];

 

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 that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting;and

 

5.     The registrant’s othercertifying officer(s) and I have disclosed, based on our most recent evaluationof internal control over financial reporting, to the registrant’s auditors andthe audit committee of the registrant’s board of directors (or personsperforming the equivalent functions):

 

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.

 
| August 6, 2004 |
|----------------|
|           | By: | /s/  Ray J. Oleson |   |
|           |   | Ray J. Oleson |   |
|           |   | Chairman of the Board and  Chief Executive Officer |   |

 

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**CERTIFICATION OF CHIEF FINANCIAL OFFICER**

**PURSUANT TO RULE 13a-14(a) AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002**

 

I,Thomas E. Dunn, certify that:

 

1.     I have reviewed thisquarterly report on Form 10-Q of SI International, Inc.;

 

2.     Based on my knowledge, thisreport does not contain any untrue statement of a material fact or omit tostate a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading withrespect to the period covered by this report;

 

3.     Based on my knowledge, thefinancial statements, and other financial information included in this report,fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periodspresented in this report;

 

4.     The registrant’s othercertifying officer(s) and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e)and 15d-15(e)) 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)    [Omitted pursuant to “Management’s Reports on Internal ControlOver Financial Reporting and Certification of Disclosure in Exchange ActPeriodic Reports,” SEC Release No. 33-8238 (June 5, 2003)];

 

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 that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting;and

 

5.     The registrant’s othercertifying officer(s) and I have disclosed, based on our most recent evaluationof internal control over financial reporting, to the registrant’s auditors andthe audit committee of the registrant’s board of directors (or personsperforming the equivalent functions):

 

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.

 
| August 6, 2004 |
|----------------|
|           | By: | /s/  Thomas E. Dunn |   |
|           |   | Thomas E. Dunn |   |
|           |   | Executive Vice President,  Chief Financial Officer and Treasurer |   |

 

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