AMENDMENT NO. 1 TO THE MARKETING, DISTRIBUTION AND SUPPLY AGREEMENT

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                                                                   EXHIBIT 10(A)

Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

                                                                  EXECUTION COPY

                                 AMENDMENT NO. 1
                                      TO THE
                  MARKETING, DISTRIBUTION AND SUPPLY AGREEMENT

     This Amendment No. 1 ("Amendment") is made as of September 26, 2007, to the
Marketing, Distribution and Supply Agreement ("Agreement") dated as of January
12, 2006 by and between DUSA Pharmaceuticals, Inc., a New Jersey corporation
having a principal office and place of business at 25 Upton Drive, Wilmington,
Massachusetts, USA 01887 (hereinafter referred to as "DUSA") and Stiefel
Laboratories, Inc., a Delaware corporation having a principal office and place
of business at 255 Alhambra Circle, Site 1000, Coral Gables, Florida, USA 33134
(hereinafter referred to as "STIEFEL")

     WHEREAS, the Parties wish to amend the Agreement as more fully set forth
below;

     NOW, THEREFORE, in consideration of the premises and mutual agreements set
forth in the Lease and this Amendment, and for good and valuable consideration,
the receipt and sufficiency of which the Parties hereby acknowledge, the Parties
hereby agree as follows:

1. All capitalized terms used herein, unless otherwise defined herein, are
defined in the Agreement.

2. The fifth "WHEREAS" clause shall be amended to read as follows:

     WHEREAS, the Parties also wish to memorialize the understanding between
      them with respect to DUSA's grant to STIEFEL of a license to use the DUSA
     Trademarks on the Products in connection with the marketing and sale of the
     Product in the Territory under the terms and conditions of the Agreement.

3. Paragraph 1.3 of the Agreement (definition of "Approved Price") shall be
deleted in its entirety and replaced with the following:

     1.3 INTENTIONALLY OMITTED.

4. The definition of "Approved Product" as set forth in Section 1.4 shall be
revised to read as follows:

      1.4 "Approved Product" shall mean any Product that shall have been granted
     all necessary approvals by the required Regulatory Authorities to allow
     STIEFEL, the exclusive right to distribute, promote and sell the Product in
     any country in the Territory pursuant to the terms of this Agreement.


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

5. Paragraph 1.13 of the Agreement shall be amended to read as follows:

     1.13 FIELD" shall mean [C.I.] uses of the Products for [C.I.] dermatology
     indications.

6. Paragraph 1.15 of the Agreement (definition of "Fiscal Year") shall be
deleted in its entirety and replaced with the following:

     1.15 INTENTIONALLY OMITTED.

7. Paragraph 1.28 shall be amended to read as follows:

     1.28 "PRICING APPROVAL" shall mean STIEFEL's receipt from CMED of
          Registration of the [C.I.] price allowed to market and sell the
          Product in Brazil within the time period stated in Section 2.4 below
          at a price of not less than [C.I.] per unit which price is [C.I.] of
          the [C.I.] government taxes to be paid [C.I.].

8. Paragraph 1.32 shall be amended to read as follows:

     1.32 "REGISTRATION" means the regulatory approvals of any applicable
          Regulatory Authorities issued in STIEFEL's name, and necessary to
          permit the commencement of the marketing and sale of the Product in
          any country in the Territory pursuant to the terms and conditions of
           this Agreement.

9. Paragraph 1.35 shall be amended to read as follows:

     1.35 "SPECIFICATIONS" of Product means the specifications for the Product
     as approved by the FDA. The Specifications may be amended from time to time
     by [C.I.] and as specifically requested by the applicable Regulatory
     Authorities.

10. Paragraph 1.39 shall be amended as follows:

     1.39 "TERRITORY" shall mean the following countries: Argentina, Brazil,
     Bolivia, Chile, Colombia, Costa Rica, Ecuador, El Salvador, Guatemala,
     Honduras, Mexico, Nicaragua, Panama, Peru, Dominican Republic, Venezuela,
     Jamaica (including the Cayman Islands), Barbados (including all surrounding
     islands including, but not limited to St. Lucia, Tortola, St. Vincent,
     Granada, Bahamas, Aruba, Bonaire, Curacao, Trinidad, Tobago, Bermuda,
     Belize), Paraguay, and Uruguay.

11. Paragraph 2.1 shall be amended to delete reference to "7.1(a)(i)" and
replace with "7.2(a)."

12. Paragraph 2.2(a) shall be amended to read as follows:

     Subject to Section 7.1, STIEFEL shall use its Commercially Reasonable
     Efforts to


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

     vigorously distribute, sell and promote the sale of the Product in the
     Field within and throughout the Territory [C.I.] so as to maximize sales in
     each country in the Territory beginning [C.I.] after the date of this
     Agreement, provided that in the event that STIEFEL is legally prohibited
     from selling the Product until Registration for the Product is obtained,
     then STIEFEL shall begin distribution and promotion of the Product in each
     country in the Territory no later than [C.I.] days after obtaining the
     Registration (and in the case of Brazil, also the Pricing Approval) from
     the appropriate Regulatory Authority in each of the respective countries in
     the Territory.

13. Paragraph 2.2(f) shall be deleted in its entirety and replaced with the
following:

     DUSA shall provide to STIEFEL, [C.I.], the number of samples and
     demonstration units (Kerastick units without active ingredient) in the
     quantity of Products more fully set forth on Schedule B, a copy of which is
     attached hereto and made a part hereof. STIEFEL shall purchase from DUSA
     all samples [C.I.] at the transfer price of [C.I.] per unit. STIEFEL shall
     purchase from DUSA all demonstration units [C.I.] at a price of [C.I.] per
     box of six (6) units.

14. Paragraph 2.4 (and its sub-parts) shall be deleted in its entirety and
replaced with the following:

     2.4 Milestone Payments; Rights of Termination Relating to Pricing Approval.

          2.4.1 Milestone Payment for all countries in the Territory except
           Brazil.

     (a)   STIEFEL shall pay DUSA within [C.I.] days of the Launch Date of the
          Product in Mexico or Argentina, whichever occurs first, a
          non-refundable, non-creditable payment of Three Hundred Seventy-Five
          Thousand U.S. Dollars (U.S. $375,000).

     Within [C.I.] days after the total cumulative number of units of Product
     ordered hereunder by STIEFEL and shipped by DUSA to STIEFEL exceeds One
     Hundred Fifty Thousand (150,000) units, STIEFEL shall make a
      non-refundable, non-creditable payment of Three Hundred Seventy-Five U.S.
     Dollars (US $375,000).[C.I.]

     (b)   Within [C.I.] days after the total cumulative number of units of
          Product ordered hereunder by STIEFEL and shipped by DUSA to STIEFEL
          exceeds Three Hundred Thousand (300,000) units, STIEFEL shall make a
          non-refundable, non-creditable payment of Three Hundred Seventy-Five
          Thousand U.S. Dollars (US $375,000).

          2.4.2 Milestone Payment for Brazil.

     (a)   Within [C.I.] days of STIEFEL's receipt of the Pricing Approval,
          STIEFEL shall pay a non-refundable, non-creditable payment of Three
          Hundred Seventy-Five Thousand Dollars (US $375,000).


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

     (b)   Within [C.I.] days after the total cumulative number of units of
          Product sold in Brazil by STIEFEL exceeds One Hundred Fifty Thousand
          (150,000) units, STIEFEL shall make a non-refundable, non-creditable
          payment of Three Hundred Seventy-Five Thousand U.S. Dollars
          (U.S.$375,000) to DUSA.

     (c)   Within [C.I.] days following the total cumulative number of units of
          Product sold in Brazil by STIEFEL exceeds Three Hundred Thousand
          (300,000) units, STIEFEL shall make a non-refundable, non-creditable
          payment of Three Hundred Seventy-Five Thousand Dollars (US$375,000) to
          DUSA.

          2.4.3 Rights of Termination Relating to Pricing Approval

     (a)   If STIEFEL (i) does not receive appropriate Pricing Approval for
          Brazil, or (ii) fails to receive approval with [C.I.] days of
          Registration and negotiations with CMED, a CMED appeal and/or other
          legal processes relating to Pricing Approval are not ongoing, STIEFEL
          shall have the right to terminate this Agreement as it relates to
          Brazil only, and its obligation under Section 2.4.2 above shall also
          immediately terminate. STIEFEL's exercise of its right under this
          Section 2.4.3 shall not by itself give rise to any claim by DUSA. In
          the event STIEFEL elects to terminate pursuant to this Section 2.4.3
          or otherwise, STIEFEL shall maintain any Registration for the Product,
          for Brazil or any other country in the Territory, until DUSA is able
          to transfer or assign such Registration to another Third Party or to
          itself. DUSA shall be responsible [C.I.] involved with STIEFEL's
          maintaining of the Registration and [C.I.]. It is understood and
          agreed that DUSA shall be responsible [C.I.] in connection with the
          CMED Pricing Approval process to date and STIEFEL shall be responsible
          [C.I.]. On an on-going basis, with respect to the effort to receive
          acceptable Pricing Approval, the Parties agree that DUSA shall be
          responsible for [C.I.] and STIEFEL shall [C.I.]. Should the current
          process not be successful as determined by the Parties, acting in good
          faith, then the executives of the Parties named in Section 4.5 of this
          Amendment shall meet promptly to discuss whether to proceed to the
          judiciary process and [C.I.] incurred for such judiciary process. If
          STIEFEL elects not to proceed with the judiciary process, then it may
          exercise its rights under this Section 2.4.3.

     (b)   If STIEFEL fails to receive Pricing Approval from CMED within [C.I.]
          days of Registration and negotiations with CMED, a CMED appeal and/or
          other legal processes relating to Pricing Approval are not ongoing,
          DUSA may elect to terminate this Agreement as to Brazil only. In such
          event, (i) STIEFEL shall maintain any Registration for the Product
          until DUSA is able to transfer or assign such Registration to another
          Third Party or to itself [C.I.]; and STIEFEL shall cooperate with DUSA
          to effect such transfer or assignment, and (ii) STIEFEL shall [C.I.]
          to DUSA for any Product and [C.I.] on purchase orders submitted to
          DUSA [C.I.].


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

15. The heading of Section 4. shall be amended to read as follows:

     4. REGISTRATIONS, PHARMACOVIGILANCE AND RECALL.

16. Section 4.1 (and its sub-parts) and Section 4.2 shall be deleted in their
entirety and replaced with the following:

     4.1 Approval and Maintenance.

     (a)   DUSA shall, [C.I.], use Commercially Reasonable Efforts to prepare the
          documents necessary for STIEFEL's submission to the Regulatory
          Authorities in Brazil for Registration of the Product for the
          treatment of Actinic Keratoses. [C.I.] shall [C.I.] for [C.I.]
          incurred on or after the Effective Date, including but not limited to,
          [C.I.] and [C.I.], in connection with seeking Registration in Brazil.
          Subject to Section 7.1 and the terms and conditions of the Safety Data
          Exchange Agreement defined below, [C.I.] shall be responsible for
          [C.I.] relating to such Registration. [C.I.] shall be responsible for
          [C.I.] incurred prior to the Effective Date in connection with seeking
          Registration in Brazil. Should DUSA receive FDA approval for the
          Product for an indication other than Actinic Keratoses, or wish to
          sell a new indication in the Territory, DUSA shall provide to STIEFEL
          copies of the relevant portions of the new drug application, in
          English, so that STIEFEL can translate and convert such information
          into the appropriate format for submission to the Regulatory
          Authorities in the Territory. Nothing herein shall be deemed to
          require DUSA to conduct any clinical development activities relating
          to use of the Product for Actinic Keratoses or any other indication,
          nor permit STIEFEL to undertake any such activities without the prior
          written consent of DUSA.

     (b)   STIEFEL shall, [C.I.] following the Effective Date, prepare, file,
          seek and maintain Registration in Brazil, which shall include, but not
          be limited to, the naming of [C.I.] and developing and implementing
          document standard operating procedures required to support the
          Product's Registration.

     (c)   For other countries in the Territory with respect to Actinic Keratoses
          and/or other indications in the Field in all countries in the
          Territory, STIEFEL shall, [C.I.], use [C.I.] to prepare, file, seek
          and maintain applications for Registration, by translating and
          converting DUSA's clinical, scientific and manufacturing proprietary
          information into the appropriate format required for submission to
          Regulatory Authorities in the Territory for Registration of the
          Product. DUSA shall provide STIEFEL, with copies of existing clinical
           and chemistry, manufacturing and controls data to support any
          Registration. STIEFEL shall [C.I.], on or after the Effective Date in
          connection with seeking these approvals.

     (d)   For clarity, [C.I.] shall mean all [C.I.] (including [C.I.]) incurred
          by a Party or any of its Affiliates in accordance with GAAP during the
          term and pursuant to this


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

           Agreement in connection with the preparation of regulatory submissions
          for the Product, the obtaining and maintenance of Registrations, and
          compliance with Registrations and requirements of such Regulatory
          Authorities needed to effect such Registration. [C.I.] shall report to
          [C.I.] within [C.I.] days after the end of each calendar [C.I.] with
          regard to Regulatory Costs incurred during such calendar [C.I.]
          (except for [C.I.] after the Effective Date relating to Registration
          in Brazil which have [C.I.]). Such report shall specify in reasonable
          detail to allow STIEFEL to verify same all expenses incurred during
          such [C.I.], and such report shall be accompanied by invoices or other
          appropriate supporting documentation for any payments to Third
          Parties. The Parties shall seek to resolve any questions related to
          such accounting statements within [C.I.] days following receipt by
          STIEFEL of DUSA's report hereunder and payment shall be made within
          [C.I.] days of STIEFEL's receipt of such report.

     (e)   The Parties shall execute a pharmacovigilance agreement, i.e., the
          Safety Data Exchange Agreement ("SDEA") in the form attached hereto as
          Schedule E and made a part hereof, concurrent with the signing of this
          Amendment by both Parties,.

     4.2   Pharmacovigilance and Recall. The Parties agree to be abide by and be
          bound to the terms of the SDEA, as stated in Section 4.1 (e) above.

17. Paragraph 4.3 of the Agreement shall be deleted in its entirety and replaced
with the following:

     4.3 INTENTIONALLY OMITTED.

18. Sections 4.4 and Section 4.5 shall be deleted in their entirety and replaced
with the following:

     4.4 Cooperation

     (a)   The Parties shall assist each other and cooperate in determining the
          optimal form of, and the necessary information to be included in
          applications for Registration of the Product in the Territory so that
          the preparation, filing, submission and maintenance of Registrations
          in the Territory are handled timely and as efficiently as reasonably
          possible. STIEFEL shall not submit any Registration to a Regulatory
          Authority without the prior written approval of DUSA, which shall not
          be unreasonably withheld, conditioned or delayed.

     (b)   From time to time, each party shall provide the other Party with a
          status of its efforts in attempting to obtain Registration for the
          Product in each country in the Territory.

     4.5   Communications; Regulatory Inspections and Notifications. The Parties


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

          recognize that due to the rules and regulations of the Regulatory
          Authorities in the Territory, the certificates of registration will,
          in most, if not all, countries of the Territory, be issued in
          STIEFEL's name. STIEFEL acknowledges and agrees that substantially all
          of the information, including without limitation, the scientific,
          clinical, chemistry, manufacturing and control information is
          proprietary information of DUSA's. STIEFEL shall not submit any
          non-routine response to an inquiry from a Regulatory Authority in the
          Territory, or any amendments or supplements to the Registrations
          without the prior written consent of DUSA which shall not be
          unreasonably withheld. The Parties agree to cooperate with each other
          in order to comply with all laws, rules and regulations of the
          Regulatory Authorities in the Territory, however if they disagree on a
           response to any inquiry from a Regulatory Authority in a particular
          country, the [C.I.] for Latin America for STIEFEL and the Executive
          [C.I.] for DUSA, or their respective successors, shall meet promptly
          in order to try to resolve their differences regarding the regulatory
          matter. If such officers are unable to resolve the regulatory issue at
          hand, DUSA shall have the final decision-making authority with respect
          to such matter, however, [C.I.] shall have the right, without being
          deemed [C.I.] the Agreement, to then [C.I.] in such country, provided
          that [C.I.] by its obligations hereunder with respect to [C.I.] of any
          [C.I.] Registration or Registration in such country, and the Parties
          shall meet in good faith to consider modifications [C.I.] under the
          Agreement which may be impacted as a result of [C.I.], including, but
          not limited to, [C.I.]. DUSA and STIEFEL each shall notify the other
          within [C.I.] (or, if such [C.I.] period ends on a non-business day,
          then prior to noon on the next following business day) of receipt of
          any notice of any governmental agency inspection, investigation or
          other inquiry, or other material governmental notice or communication,
          in each case which relates to the marketing, promotion, distribution
          and/or detailing of the Product during the term of this Agreement.
          STIEFEL and DUSA shall discuss any response to observations or
          notifications received in connection with any such inspection,
          investigation or other inquiry and each shall give the other an
          opportunity to comment upon any proposed response before it is made.
          In the event of disagreement concerning the form or content of such
          response, however, the executive officers of each Party named above
          shall meet promptly in order to try to resolve their differences. If
          such officers are unable to resolve the regulatory issue at hand, DUSA
          shall be responsible for deciding the appropriate form and content of
          any response with respect to any of its cited activities and STIEFEL
          shall be responsible for deciding the appropriate form and content of
          any response with respect to any of its cited activities. Each Party
          will provide the other Party with copies of all correspondence
          received by it from, or filed by it with any Regulatory Authority to
          the extent pertaining to the Product or its marketing, promotion or
          detailing.

19. The following shall be added to the end of Section 7.1 - "In the event that
DUSA effects any change in the manufacturing of the Product (whether that be
internal or with a Third-Party) which necessitates a regulatory submission to
any Regulatory Authority in the Territory, the


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

[C.I.] (as defined in Section 4.1(d)) associated with such regulatory submission
shall [C.I.]:

     (a)   if the change is initiated [C.I.] shall [C.I.] of such regulatory
          submissions;

     (b)   if the change is i) initiated [C.I.], ii) made upon the [C.I.] of the
          Parties, or iii) is initiated [C.I.], then [C.I.] shall [C.I.] of such
          regulatory submission [C.I.] and [C.I.] shall [C.I.] of such
          regulatory submissions [C.I.]."

20. Section 7.2(a) shall be revised by replacing all references to Section
7.1(a)(ii) with Section 7.2(a)(ii) and shall revise the first phrase of Section
7.2(a) to read as follows:

     STIEFEL shall purchase, no less than the Minimum Number of Units of the
     Product at the Purchase Price Per Unit during the applicable Time Period
     (as such terms are defined on Schedule B) (the "MINIMUM PURCHASE
     OBLIGATIONS"). For purposes of clarity, the [C.I.] royalty used in
     calculating the Purchase Price Per Unit shall be based on Net Selling Price
     for the preceding quarter.

21. The first sentence of Section 7.3(a) shall be amended to read as follows:

     Within [C.I.] prior to any Registration relating to the Product, STIEFEL
     shall provide DUSA with a forecast of STIEFEL's quantity requirements for
     the applicable commercial launch of the Product and the [C.I.] period
     following such launch.

22. The first sentence of Section 7.3(b) shall be revised to delete reference to
"[C.I.]" and to replace with "[C.I.]"; and to add the following as the last
sentence - "All orders shall be placed in [C.I.]."

23. Section 7.3(e) shall be revised to include the following sentence at the end
of such section:

     However, DUSA shall use Commercially Reasonable Efforts to meet an increase
     in demand by STIEFEL, but any DUSA failure to meet such increase shall not
     be deemed a breach of this Agreement.

24. Section 7.3(g) shall be revised to delete reference to "FOB" and to replace
with "EX-WORKS".

25. Section 7.3(i) shall be added as follows: "As part of placing each order for
the Product, and due to differing label requirements in the various countries in
the Territory, STIEFEL shall indicate in writing the country in the Territory
where such ordered Product is intended to be sold. Product purchased as being
indicated for sale in a given country shall not be sold in any other country."

26. Section 8.1 shall be deleted in its entirety and replaced with the
following:


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

     (a)   Payment of Transfer Price. Subject to Section 7.3(a), STIEFEL shall
          pay the transfer price portion of the Purchase Price Per Unit (as set
          forth on Schedule C hereto) for the quantities of Product ordered
          within [C.I.] days of the date of invoice submitted by DUSA, provided
          that DUSA [C.I.] the Product has been delivered to STIEFEL pursuant to
          Section 7.3(g).

     (b)   Royalty Reports and Payments. Within [C.I.] after the end of each
          [C.I.] (or portion thereof) beginning with the first [C.I.] ending
          after the Launch Date, STIEFEL shall deliver to DUSA a report, giving
          such particulars of the Product sold by STIEFEL and its Affiliates and
          subdistributors under this Agreement during such [C.I.]. This report
          shall set forth in reasonable detail sufficient to perform an
          accounting of royalties due to DUSA under this Agreement. Within
          [C.I.] days after the end of each [C.I.] (or portion thereof)
          beginning with the first [C.I.] after the Launch Date (i.e., [C.I.]) a
          copy of the report shall be accompanied by payment of the royalty for
          [C.I.]. Following the end of each calendar year, the Parties shall
          reconcile (true-up) any adjustments in the last payment of each year.
          These shall include at least the following, separately stated as to
          the Product:

               (i) the quantity of the Product invoiced by STIEFEL and its
               Affiliates, and subdistributors during [C.I.] and the billings
               therefor by country in the Territory;

               (ii) the calculation of royalties thereon; and

               (iii) STIEFEL's then current inventory of the Product.

     (c)   Records and Audits.

               (i) Records. STIEFEL shall keep or cause to be kept, and shall
               cause its Affiliates and subdistributors to keep, such records as
               are necessary to determine accurately, in a manner consistent
               with GAAP and this Agreement, the royalties due to DUSA under
               this Agreement.

               (ii) Audit. Such records shall be retained by STIEFEL, and
                STIEFEL shall cause its Affiliates and subdistributors to retain
               (in such capacity, the "Recording Party") for three (3) calendar
               years and, once during any applicable calendar year (unless
               otherwise required by securities law or regulations) upon ten
               (10) business days prior written notice from DUSA, such records
               shall be made available for inspection, review, and audit, and
               during normal business hours, by an independent public accounting
               firm appointed by DUSA for the sole purpose of verifying the
               Recording Party's accounting reports and payments made or to be
               made pursuant to this Agreement. Such independent public
                accounting firm shall execute a Confidential Disclosure
               Agreement, which is deemed acceptable to STIEFEL, substantially
               in the form attached hereto as Exhibit A, and


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Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

               made a part hereof, to protect STIEFEL's, or its Affiliates', or
               subdistributors' respective Confidential Information. The results
               of each inspection, if any, shall be binding upon both Parties.
               Any underpayment or overpayment determined by such inspection
               shall be paid [C.I.] after the delivery of the accountant's
               report to the Parties.

     (d)   Confidential. Such independent accounting firm shall not reveal to the
          Party seeking verification the details of its review, except for such
          information as is required to be disclosed under this Agreement, and
          such details shall be treated as Confidential Information. Each Party
          agrees to hold in strict confidence all information concerning
          payments and reports, and all information learned in the course of any
          audit or inspection (and not to make copies of such reports and
          information), except to the extent necessary for such Party to reveal
          such information in order to enforce its rights under this Agreement
          or if disclosure is required by law, regulation or judicial order.

     (e)   Costs of Audits. The results of each inspection, if any, shall be
          binding on both Parties. DUSA shall [C.I.] that in the event where the
          [C.I.] to the detriment [C.I.] of more than [C.I.] of the amount of
          any such payment, then STIEFEL shall [C.I.].

     (f)   Foreign Exchange. The rate of exchange to be used in computing the
          royalty amounts of currency equivalent in United States dollars due
          DUSA shall be made at the Wall Street Journal published rate as of the
          last business day of the relevant calendar quarter.

     (g)   Tax Withholding. In the event that any country in the Territory
          assesses a withholding tax, tariff, duty, levy, or other similar
          charge against any payments to be made by STIEFEL to DUSA pursuant to
          this Agreement("Taxes") such Taxes shall be paid in the first instance
          [C.I.] the [C.I.] under this Agreement. If for any reason [C.I.] has
          not [C.I.] such Taxes, and DUSA becomes obligated [C.I.], then DUSA
          shall [C.I.] for such Taxes [C.I.] in accordance with Section 8.1(a)
          above. DUSA shall secure and promptly send to STIEFEL [C.I.] or [C.I.]
          by DUSA for the benefit of STIEFEL. The Parties shall cooperate
          reasonably with each other to ensure that any amounts required to be
          [C.I.] are reduced in amount to the fullest extent permitted by law.
          [C.I.] shall be made, or a [C.I.] shall be [C.I.], if STIEFEL
          furnishes a document from the appropriate tax authorities to DUSA
          certifying that the payments are exempt from withholding Taxes or
          subject to reduced tax rates, according to the applicable convention
          for the avoidance of double taxation.

     (h)   Method of Payment. All payments shall be made in United States
          dollars, by wire transfer, preferably Automated Clearing House
          ("ACH"), of immediately available funds [C.I.].

27. Section 8.4 shall be deleted in its entirety and not replaced.


                                                                         PAGE 10

<PAGE>

Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

28. Section 9.4(d) - the last sentence shall be revised to read as follows:

     In the event that [C.I.] Product is required, it shall be [C.I.] unless
     otherwise agreed to in writing by STIEFEL.

29. Section 11.2 shall be revised to add the following language to the end of
such section:

     but all such improvements, to the extent they relate to the Product, shall
     be considered part of the grant made to STIEFEL herein pursuant to Sections
     2 and 3.1; provided, however, that if the [C.I.] such improved Product is
     [C.I.] the Product [C.I.] improved Technical Information, the grant shall
     be [C.I.].

30. Section 18.2(d) shall be revised to delete references to Sections 7.1(a)(ii)
and 2.4(c) and replace them with Sections 4.5 (but only as it relates to a
particular country in the Territory in which STIEFEL will be assigning or
transferring a Registration to DUSA or its designee), 7.2(a)(ii) and 2.4.3(a),
respectively.

31. Section 18.2(e) shall be revised to delete reference to Section 2.4(b) and
replace with Section 2.4.3(b).

32. Section 18.2(g) shall be deleted in its entirety and replaced with the
following:

     (g) INTENTIONALLY OMITTED.

33. Section 25 shall be revised to read as follows "The Agreement, as may be
amended by the written agreement of the Parties, from time to time, together
with all Schedules and Exhibits, incorporates the entire understanding of the
Parties and revokes and supersedes any and all agreements, contracts,
understandings or arrangements that might have existed heretofore between the
Parties regarding the subject matter hereof.

34. Schedule B attached to the Agreement shall be deleted and replaced with the
attached Schedule B.

35. Schedule C attached to the Agreement shall be deleted and replaced with the
attached Schedule C.


                                                                         PAGE 11

<PAGE>

Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

IN WITNESS WHEREOF, each of the Parties has caused this Amendment to be executed
in multiple counterparts by its duly authorized representative.

STIEFEL LABORATORIES, INC.


By: /s/ William Humphries
    ---------------------------------
    William Humphries
    Chief Commercial Officer


DUSA PHARMACEUTICALS, INC.


By: /s/ William F. O'Dell
    ---------------------------------
    William F. O'Dell
    Executive Vice President,
    Sales and Marketing


                                                                          PAGE 12

<PAGE>

Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

                                   SCHEDULE B

             MINIMUM PURCHASE OBLIGATIONS AND PRODUCT FREE OF CHARGE

The Minimum Purchase Obligations for Levulan(R) Kerastick(R) shall be as
follows:

1 - All countries in the territory, except Brazil

<TABLE>
<CAPTION>
    TIME PERIOD       MINIMUM NUMBER OF UNITS
    -----------       -----------------------
<S>                   <C>
First Time Period           [C.I.]
Second Time Period          [C.I.]
Third Time Period           [C.I.]
Fourth Time Period          [C.I.]
Fifth Time Period           [C.I.]
</TABLE>

DUSA shall supply Stiefel with [C.I.] units of Levulan Kerastick in U.S
packaging, [C.I.]. The products must be delivered to Stiefel when the product is
launched in Mexico, or otherwise, agreed between the parties.

2 - Only Brazil

<TABLE>
<CAPTION>
    TIME PERIOD       MINIMUM NUMBER OF UNITS
    -----------       -----------------------
<S>                   <C>
First Time Period            [C.I.]
Second Time Period           [C.I.]
Third Time Period            [C.I.]
Fourth Time Period           [C.I.]
Fifth Time Period            [C.I.]
</TABLE>

Obligations for Levulan(R) Kerastick(R) shall be determined by [C.I.] no later
than [C.I.] months prior to the end of calendar year 2011.

DUSA shall supply Stiefel with [C.I.] units of Levulan Kerastick in U.S.
packaging, [C.I.]. The products must be delivered to Stiefel when the product is
launched in Brazil, or otherwise, agreed between the parties.

Additionally to the [C.I.] products to support the product launching, DUSA will
also provide Stiefel with:

     a.    [C.I.] products for any Clinical Study with approved protocol;

     b.    [C.I.] products with U.S. labeling (Kerastick units [C.I.].


                                                                          PAGE 13

<PAGE>

Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

                                   SCHEDULE C

SUPPLY PRICE AND [C.I.] OF SUPPLY - ALL COUNTRIES IN THE TERRITORY

"PURCHASE PRICE PER UNIT", with respect to units of the Product that are
purchased for sales in a country in the Territory, shall mean [C.I.] plus [C.I.]
based on the Net Selling Price received by STIEFEL for the Products. For
purposes hereof, the Net Selling Price shall mean the price charged [C.I.], to
end-users (i.e., physician or hospital customers, or the like) in the [C.I.]
after [C.I.] on units of the Product sold.

In the event at any time the Net Selling Price Per Unit for sales in a country
in the Territory in a given calendar quarter, as expressed in U.S. Dollars using
the current average daily applicable local currency / U.S. Dollar exchange rate,
is [C.I.] U.S. Dollars ([C.I.] USD) (the "Event"), then STIEFEL shall [C.I.] Net
Selling Price in the applicable local currency [C.I.] of such Purchase Price Per
Unit [C.I.] U.S. Dollars ([C.I.] USD)provided that [C.I.] prior written notice
from STIEFEL given after such the Event, STIEFEL [C.I.]; provided further that
upon giving such notice to DUSA, [C.I.]. beginning [C.I.] and continuing until
the [C.I.] U.S. Dollars ([C.I.] USD) for a period of not less than [C.I.] weeks.


                                                                         PAGE 14

<PAGE>

Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

                                    EXHIBIT A

                         CONFIDENTIAL DISCLOSURE AGREEMENT

This Agreement is entered into as of the __ day of ________, 200_, by and
between Stiefel Laboratories, Inc. ("Stiefel"), a Delaware corporation with an
office and place of business at 255 Alhambra Circle, Coral Gables, Florida 33134
and _________________ ("Company"), with an office and place of business at
_____________________________. Stiefel and Company are also jointly referred to
herein as "Parties," and individually as a "Party."

1. Company shall be conducting an audit of Stiefel's accounting reports and
payment records solely as it relates to Stiefel's obligations under the
Marketing, Distribution and Supply Agreement, as amended between Stiefel and
DUSA Pharmaceuticals, Inc.. The Parties anticipate that in the course of such
activities, Stiefel may disclose to Company certain of Stiefel's inventions,
trade secrets, know how, data, materials, or other information (together,
"Information") that Stiefel considers confidential and/or proprietary.

2. As used in this Agreement, "Confidential Information" means all Information
disclosed by Stiefel to Company, whether by oral or written communication,
delivery, demonstration or access.

3. Company shall use Confidential Information only in the course of the
activities described above or as otherwise directed in writing by Stiefel.
Company agrees that, for a period of [C.I.] following Stiefel's disclosure of
Confidential Information to Company, Company shall:

     (i)   Not disclose such Confidential Information to any other person or
          entity other than DUSA without Stiefel's prior written consent; and

     (ii) protect such Confidential Information from further disclosure in the
          same manner as it protects its own information of a similar nature
           (but in no event with less than a reasonable standard of care).

4. Stiefel grants no present or future rights or license, under any of its
inventions, patents, copyrights, trade secrets, trademarks or other property, to
Company with respect to Confidential Information.

5. Company's obligations specified in Section 3 shall not apply to any
Information that Company can demonstrate:

     (i)   is or becomes known or generally available to the public, through no
          act or omission of Company and without any wrongful act of any third
          party;

     (ii) is or becomes known to Company through disclosure by any third party,
          without any wrongful act of Company or such third party;

     (iii) is subsequently disclosed by Company pursuant to the requirement of a
          statute, regulation, or judicial or administrative order requiring
          disclosure thereof, provided that Company first provides Stiefel with
          written notice of any such


                                                                          PAGE 15

<PAGE>

Note: Certain portions of this document have been marked "[C.I.]" to indicate
that confidential treatment has been requested for this confidential
information. The confidential portions have been omitted and filed separately
with the Securities and Exchange Commission.

          requirement, promptly upon learning of the requirement; or

     (iv) has been or is subsequently developed independently by Company,
          without any use of Confidential Information.

6. Company shall, upon Stiefel's written request, return to Stiefel its
Confidential Information (to include all copies and reproductions thereof and
all information prepared by Company which incorporates Confidential
Information).

7. The Parties agree that if Company breaches any of its obligations hereunder,
money damages will not afford Stiefel an adequate remedy. Therefore, if any such
breach occurs, in addition to any other remedies as may be provided by law,
Stiefel shall have the right to seek such equitable relief as it deems
reasonably necessary to enforce its rights hereunder (whether temporary or
permanent injunctive relief, or otherwise). Notwithstanding the foregoing, the
Parties expressly agree that neither Party shall be liable to the other Party
for incidental, consequential, punitive, special or exemplary damages with
respect to any breach of this Agreement.

8. Neither Party may assign all or any part of its rights or obligations
hereunder without the other Party's prior wri