HART & TRINEN, LLP
                                ATTORNEYS AT LAW
                             1624 Washington Street
                                Denver, CO 80203
William T. Hart, P.C.               ________          Email:  harttrinen@aol.com
Donald T. Trinen                                      Facsimile:  (303) 839-5414
                                 (303) 839-0061

                                  July 12, 2007

Tara Harkins
Securities and Exchange Commission
Division of Corporation Finance
100 F Street, NE
Washington, DC 20549

      Re:   Security Devices International Inc.
            Registration Statement on Form SB-2
            File No. 333-143301

     This office represents Security Devices International Inc. (the "Company").
In reference to the Staff's  letter dated June 21, 2007 we would like to address
comments 1, 18, 20, 21 and 22 before  filing an  amendment  to the  registration
statement.


C-1     Since the accountants are not being paid on a contingency basis the
        disclosure required by Item 509 of Regulation S-B is not required.

C-18    Since the prospectus will not reference the accountants as experts there
        is no need for the accountants to refer to their firm as "Experts" in
        their consent.

C-20,
21, 22  The proposed modification to the "Controls and Procedures" section of
        the Company's 10-Q is shown below:

           Sheldon Kales, the Company's Chief Executive and Rakesh Malhotra, the
           Company's Principal Financial Officer, have evaluated the
           effectiveness of the Company's disclosure controls and procedures (as
           defined in Rule 13a-15(e) of the Securities Exchange Act of 1934) as
           of the end of the period covered by this report, and in their opinion
           the Company's disclosure controls and procedures are effective. There
           were no changes in the Company's internal controls over financial
           reporting that occurred during the fiscal quarter that have
           materially affected, or are reasonably likely to materially affect,
           the Company's internal controls over financial reporting.


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      Please advise if our proposed responses to these comments are acceptable
to the Staff.

                                           Very Truly Yours,

                                           HART & TRINEN, L.L.P.



                                           William T. Hart




WTH:ap









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