**Exhibit 31.1**

**CERTIFICATION PURSUANT TO SECTION 302(A) OF THE SARBANES-OXLEY ACT OF 2002**

| I, G. Patrick Lynch,   certify that: |
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| 1.                                   | I have reviewed this   quarterly report on Form 10-QSB of Northern Technologies International   Corporation; |
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| 2.                                   | Based on my knowledge,   this report does not contain any untrue statement of a material fact or omit   to state a material fact necessary to make the statements made, in light of   the circumstances under which such statements were made, not misleading with   respect to the period covered by this report; |
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| 3.                                   | Based on my knowledge, the   financial statements, and other financial information included in this   report, fairly present in all material respects the financial condition,   results of operations and cash flows of the small business issuer as of, and   for, the periods presented in this report; |
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| 4.                                   | The small business   issuer’s other certifying officers and I are responsible for establishing and   maintaining disclosure controls and procedures (as defined in Exchange Act Rules   13a-15(e) and 15d-15(e)) for the small business issuer and have: |
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|                                 | (a) | Designed such disclosure   controls and procedures, or caused such disclosure controls and procedures to   be designed under our supervision, to ensure that material information relating   to the small business issuer, including its consolidated subsidiaries, is   made known to us by others within those entities, particularly during the   period in which this report is being prepared; |
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|                                 | (b) | Evaluated the   effectiveness of the small business issuer’s disclosure controls and   procedures and presented in this report our conclusions about the   effectiveness of the disclosure controls and procedures, as of the end of the   period covered by this report based on such evaluation; and |
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|                                 | (c) | Disclosed in this report   any change in the small business issuer’s internal control over financial   reporting that occurred during the small business issuer’s fourth quarter   that has materially affected, or is reasonably likely to materially affect,   the small business issuer’s internal control over financial reporting; and |
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| 5.                                   | The small business   issuer’s other certifying officers and I have disclosed, based on our most   recent evaluation of internal controls over financial reporting, to the small   business issuer’s auditors and the audit committee of the small business   issuer’s board of directors (or persons performing the equivalent function): |
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|                                 | (a) | All significant   deficiencies and material weaknesses in the design or operation of internal   controls over financial reporting which are reasonably likely to adversely   affect the small business issuer’s ability to record, process, summarize and   report financial information; and |
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|                                 | (b) | Any fraud, whether or not   material, that involves management or other employees who have a significant   role in the small business issuer’s internal controls over financial   reporting. |

 

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|                       | G.   Patrick Lynch                      |
| Date:  April 11, 2007 | President   and Chief Executive Officer |