**Exhibit 31(a)**

 

**DUSA PHARMACEUTICALS, INC.**

 

**CERTIFICATION**

 

I, D. Geoffrey Shulman, certify that:

 

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

 

2.               Based on my knowledge, this quarterlyreport 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 quarterly report;

 

3.               Based on my knowledge, the financialstatements, and other financial information included in this quarterly 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 quarterly report;

 

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)) for the registrant and we have:

 

a)                          Designed such disclosurecontrols and procedures, or caused such disclosure controls and procedures tobe designed under our supervision, to ensure that material information relatingto the registrant, including its consolidated subsidiaries, is made known to usby others within those entities, particularly during the period in which thisquarterly report is being prepared;

 

b)                         Evaluated the effectiveness ofthe registrant’s disclosure controls and procedures and presented in thisreport our conclusions about the effectiveness of the disclosure controls andprocedures, as of the end of the period covered by this quarterly report basedon such evaluation; and

 

c)                          Disclosed in this report anychange in the registrant’s internal control over financial reporting thatoccurred during the registrant’s most recent fiscal quarter (the registrant’sfourth fiscal quarter in the case of an annual report) that 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 deficienciesand material weaknesses in the design or operation of internal control overfinancial reporting which are reasonably likely to adversely affect the registrant’sability to record, process, summarize and report financial information; and

 

b)                         Any fraud, whether or notmaterial, that involves management or other employees who have a significantrole in the registrant’s internal control over financial reporting.

 

 
| Date: November 11, 2004 | /s/ D. Geoffrey Shulman                                              |   |
|-------------------------|----------------------------------------------------------------------|--------|
|                    | D. Geoffrey Shulman                                                  |
|                    | President and Chief Executive Officer  (principal executive officer) |

 

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