**Exhibit 31.1**

 

**CERTIFICATION OF CHIEF EXECUTIVE OFFICERPURSUANT 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 havereviewed this quarterly report on Form 10-Q/A of SI International, Inc.; 

 

2.  Based on my knowledge, this reportdoes not contain any untrue statement of a material fact or omit to state amaterial 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, the financialstatements, and other financial information included in this report, fairlypresent in all material respects the financial condition, results of operationsand cash flows of the registrant as of, and for, the periods presented in thisreport; 

 

4.  The registrant’s other certifyingofficer and I are responsible for establishing and maintaining disclosurecontrols 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 13c-15(f) and 15d-15(f)) for the registrant and have: 

 

(a)  Designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to be designedunder our supervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which thisreport is being prepared; 

 

(b)  [Omitted pursuant to“Management’s Reports on Internal Control Over Financial Reporting andCertification of Disclosure in Exchange Act Periodic Reports,” SEC Release No.33-8238 (June 5, 2003).]

 

(c)  Evaluated the effectiveness of theregistrant’s disclosure controls and procedures and presented in this reportour conclusions about the effectiveness of the disclosure controls andprocedures, as of the end of the period covered by this report based on suchevaluation; and 

 

(d)  Disclosed in this report any changein the registrant’s internal control over financial reporting that occurredduring the registrant’s most recent fiscal quarter that has materiallyaffected, or is reasonably likely to materially affect, the registrant’sinternal control over financial reporting; and

 

5.  The registrant’s other certifyingofficer and I have disclosed, based on our most recent evaluation of internalcontrol over financial reporting, to the registrant’s auditors and the auditcommittee of the registrant’s board of directors (or persons performing theequivalent functions):

 

(a)  All significant deficiencies andmaterial weaknesses in the design or operation of internal control overfinancial reporting which are reasonably likely to adversely affect theregistrant’s ability to record, process, summarize and report financialinformation; and 

 

(b)  Any fraud, whether or not material,that involves management or other employees who have a significant role in theregistrant’s internal control over financial reporting.

 

 
| Date:  | December  1, 2003 |   |                                                                  |   |
|--------|-------------------|--------|-----------------------------------------------------------------------|--------|
|   |              |   |                                                                  |
|   |              |   |                                                                  |
|   |              | By:    | /s/ Ray J. Oleson                                                     |
|   |              |   | Ray J. Oleson**Chairman of the Board and****Chief Executive Officer** |
|        |                   |        |                                                                       |        |  |

 

1

----

 

**CERTIFICATION OF CHIEF FINANCIAL OFFICERPURSUANT 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/A of SI International, Inc.; 

 

2.  Based on my knowledge, this reportdoes not contain any untrue statement of a material fact or omit to state amaterial 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, the financialstatements, and other financial information included in this report, fairlypresent in all material respects the financial condition, results of operationsand cash flows of the registrant as of, and for, the periods presented in thisreport; 

 

4.  The registrant’s other certifyingofficer and I are responsible for establishing and maintaining disclosurecontrols 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 the registrant and have: 

 

(a)  Designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to be designedunder our supervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which thisreport is being prepared; 

 

(b)  [Omitted pursuant to“Management’s Reports on Internal Control Over Financial Reporting andCertification of Disclosure in Exchange Act Periodic Reports,” SEC Release No.33-8238 (June 5, 2003).]

 

(c)  Evaluated the effectiveness of theregistrant’s disclosure controls and procedures and presented in this reportour conclusions about the effectiveness of the disclosures controls andprocedures, as of the end of the period covered by this report based on suchevaluation; and 

 

(d)  Disclosed in this report any changein the registrant’s internal control over financial reporting that occurredduring the registrant’s most recent fiscal quarter that has materiallyaffected, or is reasonably likely to materially affect, the registrant’sinternal control over financial reporting; and

 

5.  The registrant’s other certifyingofficer and I have disclosed, based on our most recent evaluation of internalcontrol over financial reporting, to the registrant’s auditors and the auditcommittee of the registrant’s board of directors (or persons performing theequivalent functions):

 

(a)  All significant deficiencies andmaterial weaknesses in the design or operation of internal control overfinancial 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 or other employees who have a significant role in theregistrant’s internal control over financial reporting.

 

 
| Date:  | December  1, 2003 |   |                                                                               |
|--------|-------------------|--------|------------------------------------------------------------------------------------|
|   |              |   |                                                                               |
|   |              |   |                                                                               |
|   |              | By:    | /s/ Thomas E. Dunn                                                                 |
|   |              |   |                                                                               |
|   |              |   | Thomas E. Dunn**Executive Vice President,  Chief Financial Officer and Treasurer** |
|        |                   |        |                                                                                    |  |

 

2

----