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                                                                    EXHIBIT 31.1

                   SARBANES-OXLEY SECTION 302(A) CERTIFICATION

I, D. Geoffrey Shulman, Chief Executive Officer and Chief Financial Officer,
certify that:

1.   I have reviewed this quarterly report on Form 10-Q of DUSA Pharmaceuticals,
     Inc.;

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;

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 registrant as of, and for, the periods presented in this report;

4.   I am responsible for establishing and maintaining disclosure controls and
     procedures (as defined in Exchange Act Rules 13a-15(d) and 15d-15(e)) for
     the registrant and have:

     a)    Designed such disclosure controls and procedures, or caused such
           disclosure controls and procedures to be designed under my
           supervision, to ensure that material information relating to the
           registrant, including its consolidated subsidiaries, is made known to
           me by others within those entities, particularly during the period in
           which this report is being prepared;

     b)    Evaluated the effectiveness of the registrant's disclosure controls
           and procedures and presented in this report my 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

     c)    Disclosed in this report any change in the registrant's internal
           control over financial reporting that occurred during the
           registrant's most recent fiscal quarter (the registrant's fourth
           fiscal quarter in the case of an annual report) that has materially
           affected, or is reasonably likely to materially affect, the
           registrant's internal control over financial reporting; and

5.   I have disclosed, based on my most recent evaluation of internal control
     over financial reporting to the registrant's auditors and the audit
     committee of registrant's board of directors (or persons performing the
     equivalent function):

     a)    all significant deficiencies and material weaknesses in the design or
           operation of internal control over financial reporting which are
           reasonably 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 the registrant's internal
           control over financial reporting.

Date: August 12, 2003                    /s/ D. Geoffrey Shulman
                                         -----------------------
                                         D. Geoffrey Shulman
                                         President, Chief Executive Officer
                                         (Principal Executive Officer), and
                                         Chief Financial Officer (Principal
                                         Financial Officer)