<PAGE>   1

                                                                     EXHIBIT 4.1


                                     FORM OF
                                STOCK CERTIFICATE

NUMBER                      DUSA PHARMACEUTICALS, INC.                    SHARES
                           Incorporated under the law
DUSA _____                  of the State of New Jersey                    ______



                                                             See reverse for
                                                             Certain Definitions

                                                             CUSIP 266898 10 5

THIS CERTIFIES THAT





is the owner of

                      FULLY PAID AND NON-ASSESSABLE SHARES
                      OF THE COMMON STOCK, NO PAR VALUE, OF

DUSA Pharmaceuticals, Inc., (hereinafter called the"Corporation"),transferable
only on the books of the Corporation by the holder hereof in person or by duly
authorized attorney upon surrender of this certificate properly endorsed.

         This certificate is not valid until countersigned and registered by the
transfer agent and registrar of the Corporation.

         The shares represented by this certificate are transferable at the
corporate offices of American Stock Transfer & Trust Company in New York, New
York or at the corporate offices of Montreal Trust Company of Canada in Toronto,
Ontario.

         IN WITNESS WHEREOF, the facsimile seal of the Corporation and the
facsimile signatures of its duly authorized officers.

Dated:



<TABLE>
<S>                               <C>                                <C>             <C>
Countersigned and Registered      Countersigned and Registered       [Seal]          President
  AMERICAN STOCK TRANSFER            MONTREAL TRUST COMPANY
      & TRUST COMPANY                       OF CANADA
                              OR

    Authorized Signature             Authorized Signature                            Secretary
</TABLE>
<PAGE>   2
                          [REVERSE SIDE OF CERTIFICATE]

                           DUSA PHARMACEUTICALS, INC.

         The following abbreviations, when used in the inscription on the face
of this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations.

<TABLE>
<S>                                                 <C>    
         TEN COM - as tenants in common             UNIF GIFT MIN ACT-_________Custodian __________
                                                                       (Cust)              (Minor)
         TEN ENT - as tenants by the entireties                        
         JT TEN  - as joint tenants with rights                       under Uniform Gifts to Minors
                     of survivorship and not as                       Act _________________________
                     tenants in common                                            (State)
</TABLE>

   FOR VALUE RECEIVED,_________________ HEREBY SELL, ASSIGN AND TRANSFER UNTO:

   Please insert social security, social insurance
   or taxpayer identification number of assignee

   _____________________________________________
   _____________________________________________



________________________________________________________________________________
             Please print or typewrite Name and Address of Assignee

________________________________________________________________________________


___________________________________________________________  SHARES REPRESENTED
BY THE WITHIN CERTIFICATE, AND DO HEREBY IRREVOCABLY CONSTITUTE AND APPOINT

____________________________________________________________________  ATTORNEY
TO TRANSFER THE SAID SHARES ON THE BOOKS OF THE WITHIN-NAMED CORPORATION WITH
FULL POWER OF SUBSTITUTION IN THE PREMISES.

Dated: _______________________        X _____________________________________
                                                    (Signature)
                                       

                                        _____________________________________
                                                 (Please Print Name)

______________________________          _____________________________________
         Signature Guaranteed                         (Address)

                                        _____________________________________
                                         Social Security, Social Insurance or 
                                            Taxpayer Identification Number

THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON
THE FACE OF THIS COMMON STOCK CERTIFICATE IN EVERY PARTICULAR, WITHOUT
ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATSOEVER, AND MUST BE GUARANTEED BY A
COMMERCIAL BANK OR TRUST COMPANY OR A MEMBER FIRM OF THE AMERICAN STOCK
EXCHANGE, NEW YORK STOCK EXCHANGE, PACIFIC STOCK EXCHANGE, MIDWEST STOCK
EXCHANGE, OR TORONTO STOCK EXCHANGE.

This certificate also evidences and entitles the holder hereof to certain Rights
as set forth in the Rights Agreement between DUSA Pharmaceuticals, Inc., (the
"Company") and American Stock Transfer & Trust Company (the "Rights Agent")
dated as of September 26, 1997, (the "Rights Agreement"), the terms of which are
hereby incorporated by reference and a copy of which is on file at the principal
offices of the Company. Under certain circumstances, as set forth in the Rights
Agreement, such Rights will be evidenced by separate certificates and will no
longer be evidenced by this certificate. The Company will mail to the holder of
this certificate a copy of the Rights Agreement, as in effect on the date of
mailing, without charge promptly after receipt of a written request therefor.
Under certain circumstances set forth in the Rights Agreement, Rights issued to,
or held by, any Person who is, was, or becomes an Acquiring Person, and Adverse
Person or any Affiliate or Associate of an Acquiring Person or an Adverse Person
(as such terms are defined in the Rights Agreement), whether currently held by
or on behalf of such Person or by any subsequent holder, may be null and void.
The Rights shall not be exercisable, and shall be void so long as held by a
holder in any jurisdiction where the requisite qualification to the issuance to
such holder, or the exercise by such holder, of the Rights in such jurisdiction
shall not have been obtained or be obtainable.


           AMERICAN BANKNOTE COMPANY          PRODUCTION COORDINATOR SUE McNAMEE
                                                         215-830-2158
               680 BLAIR MILL ROAD                PROOF OF OCTOBER 22, 1997
                HORSHAM, PA 19044                            DUSA
                   215-657-3480                          H 53296PATCH

      ____________________________________     _________________________________
      SALESPERSON    R. JOHNS 212-557-9100     Opr.           JH             NEW

      ____________________________________     _________________________________
      /home/jm/inprogress/home11/DUSA53296          /net/banknote/home/11/D