<PAGE>

                CERTIFICATE OF POWERS, DESIGNATION, PREFERENCES,
                             RIGHTS AND LIMITATIONS

                                       OF

                      SERIES C CONVERTIBLE PREFERRED STOCK

                                       OF

                                 COCENSYS, INC.

                         (Pursuant to Section 151 of the
                        Delaware General Corporation Law)


     COCENSYS, INC., a corporation organized and existing under the General 
Corporation Law of the State of Delaware (hereinafter called the 
"Corporation"), hereby certifies that the following resolution was adopted by 
the Board of Directors of the Corporation as required by Section 151 of the 
General Corporation Law at a meeting duly called and held on April 29, 1997:

               RESOLVED, that pursuant to the authority granted to and
          vested in the Board of Directors of the Corporation in
          accordance with the provisions of its Amended and Restated
          Certificate of Incorporation, the Board of Directors hereby
          creates a series of Preferred Stock, par value $.001 per
          share, of the Corporation and hereby states the designation
          and number of shares, and fixes the relative rights,
          preferences and limitations thereof (in addition to the
          provisions set forth in the Restated Certificate of
          Incorporation of the Corporation, which are applicable to
          the Preferred Stock of all classes and series), as follows:

          Series C Convertible Preferred Stock:

               SECTION 1.  DESIGNATION AND AMOUNT.  One Hundred
          Thousand (100,000) shares of Preferred Stock, $.001 par
          value, are designated "Series C Convertible Preferred Stock"
          with the rights, preferences, privileges and restrictions
          specified herein (the 

                                       1.

<PAGE>

          "Series C Preferred Stock").  Such number of shares may be not 
          increased or decreased without the consent of the holder.

               SECTION 2.  DIVIDENDS AND DISTRIBUTIONS.  The holders
          of the Series C Preferred Stock shall be entitled to
          receive, when, as and if declared by the Board of Directors,
          out of funds legally available therefor, dividends at the
          rate per share equal to any dividend declared or paid per
          share to the Common Stock of the Corporation ("Common
          Stock").  The right to such dividends on the Series C
          Preferred Stock shall be non-cumulative.

               SECTION 3.  VOTING RIGHTS.    Except as set forth
          herein, or as otherwise provided by law, holders of Series C
          Preferred Stock shall have no special voting rights and
          their consent shall not be required (except to the extent
          they are entitled to vote with holders of Common Stock as
          set forth herein) for taking any corporate action.

               SECTION 4.  LIQUIDATION PREFERENCE. In the event of any
          liquidation, dissolution or winding up of the Corporation,
          either voluntary or involuntary (a "Liquidation Event"), 
          the holders of the Series C Preferred Stock shall be
          entitled to receive, prior and in preference to any
          distribution of any of the assets or surplus funds of the
          Corporation to the holders of the Common Stock or Junior
          Preferred Stock of the Corporation, an amount per share (as
          adjusted for any combinations, consolidations, stock
          distributions or stock dividends with respect to such
          shares) equal to the quotient of (a) $5,000,000 divided by
          (b) the number of shares of Series C Preferred Stock issued
          and outstanding as of the date of such Liquidation Event. 
          If upon the occurrence of such Liquidation Event, the assets
          and funds thus distributed among the holders of the Series C
          Preferred Stock shall be insufficient to permit the payment
          to such holders of the full aforesaid preferential amount,
          then the entire assets and funds of the Corporation legally
          available for distribution shall be distributed among the
          holders of the Series C Preferred Stock in proportion to the
          shares of Series C Preferred Stock then held by them.

               SECTION 5.  CONVERSION.  Subject to the limitations set
          forth in Subsection (B) below, the Series C Preferred Stock
          shall convert only as follows:  

               (A)  CONVERSION AT HOLDER'S OPTION.  At any time after
          May 11, 1999, the Series C Preferred Stock shall be
          convertible, in whole or in part, on a maximum of three
          occasions, at the 

                                       2.

<PAGE>

          option of the holder, into such number of fully paid and 
          nonassessable shares of Common Stock equal to the quotient 
          of (a) the product of $50 and the number of shares of 
          Series C Preferred Stock being converted, divided by (b) 
          the Conversion Price.  

          The "Conversion Price" shall be equal to the greater of:

               (i)  $5.43 or

               (ii) the lesser of:

                    (x) the Future Market Price x 0.80 or

                    (y) $7.76;

          PROVIDED, HOWEVER, that if the Future Market Price is less
          than $3.88, the Conversion Price shall be $4.37.

          The "Future Market Price" set forth above shall be the
          average closing price of the Common Stock for the period
          commencing on the 23rd trading day prior to the date upon
          which the holder delivers notice to the Corporation of such
          conversion (each, a "Conversion Date") and ending on the
          third trading day prior to the Conversion Date, as reported
          in the WALL STREET JOURNAL, WESTERN EDITION.

               (B)  ADJUSTMENTS FOR COMBINATIONS OR SUBDIVISIONS OF
          COMMON STOCK.  In the event the Corporation at any time or
          from time to time shall declare or pay any dividend on the
          Common Stock payable in Common Stock or in any right to
          acquire Common Stock, or shall effect a subdivision of the
          outstanding shares of Common Stock into a greater number of
          shares of Common Stock (by stock split, reclassification or
          otherwise), or in the event the outstanding shares of Common
          Stock shall be combined or consolidated, by reclassification
          or otherwise, into a lesser number of shares of Common
          Stock, then the maximum and minimum number of shares of
          Common Stock into which the Series C Preferred Stock may be
          converted, shall be proportionately decreased or increased,
          as appropriate.

               (C)  MECHANICS OF CONVERSION.  Before any holder of
          Series C Preferred Stock shall be entitled to receive shares
          of Common Stock, he shall surrender the certificate or
          certificates thereof, duly endorsed, at the office of the
          Corporation or of any transfer agent for such stock, and
          shall state therein the name or 

                                       3.

<PAGE>

          names in which he wishes the certificate or certificates 
          for shares of Common Stock to be issued.  The Corporation 
          shall, as soon as practicable thereafter, issue and deliver 
          at such office to such holder of Series C Preferred Stock, 
          a certificate or certificates for the number of shares of 
          Common Stock to which he shall be entitled as aforesaid.  
          Such conversion shall be deemed to have been made on the 
          Conversion Date, and the person or persons entitled to 
          receive the shares of Common Stock issuable upon such 
          conversion shall be treated for all purposes as the record 
          holder or holders of such shares of Common Stock on such 
          date.  

               (D)  RESERVATION OF STOCK ISSUABLE UPON CONVERSION. 
          The Corporation shall at all times reserve and keep
          available out of its authorized but unissued shares of
          Common Stock, solely for the purpose of effecting the
          conversion of the shares of the Series C Preferred Stock,
          such number of its shares of Common Stock as shall from time
          to time be sufficient to effect the conversion of all
          outstanding shares of the Series C Preferred Stock.

               (E)  FRACTIONAL SHARES.  No fractional share shall be
          issued upon the conversion of any share or shares of Series
          C Preferred Stock.  All shares of Common Stock (including
          fractions thereof) issuable upon conversion of Series C
          Preferred Stock shall be aggregated for purposes of
          determining whether the conversion would result in the
          issuance of any fractional share.  If, after the
          aforementioned aggregation, the conversion would result in
          the issuance of a fraction of a share of Common Stock, the
          Corporation shall, in lieu of issuing any fractional share,
          pay the holder otherwise entitled to such fraction a sum in
          cash equal to the closing price of the Common Stock on the
          date of conversion, multiplied by such fraction.

               (F)  REORGANIZATION, RECLASSIFICATION, CONSOLIDATION,
          MERGER OR SALE.  If any (i) reorganization of the capital
          stock of the Corporation, (ii) consolidation or merger of
          the Corporation in which the Corporation is not the
          surviving corporation, or (iii) sale of all or substantially
          all of the Corporation's assets to another corporation
          (each, an "Event") shall be effected in such a way that
          holders of Common Stock shall be entitled to receive
          securities, cash or other assets or property, the first
          Conversion Date shall be accelerated to the date immediately
          preceding such Event, or such other date necessary to assure
          that any holder of Series C Preferred Stock receives such
          shares of stock, securities or other assets or property as
          may be issued or payable with respect to or in exchange for
          shares of Common Stock.

                                       4.

<PAGE>

               SECTION 6.     NO REDEMPTION.  The shares of Series C
          Preferred Stock shall not be redeemable. 

               SECTION 7.  AMENDMENT.  The Restated Certificate of
          Incorporation of the Corporation shall not be amended in any
          manner which would materially alter or change the powers,
          preferences or special rights of the Series C Preferred
          Stock so as to affect them adversely without the affirmative
          vote of the holders of at least two-thirds of the
          outstanding shares of Series C Preferred Stock, voting
          together as a single class.

                                       5.

<PAGE>

     IN WITNESS WHEREOF the undersigned have executed this certificate as of May
12, 1997.


                                   /s/ F. Richard Nichol, Ph.D.
                                   --------------------------------------------
                                   President and Chief Executive Officer



                                   /s/ Alan C. Mendelson
                                   --------------------------------------------
                                   Secretary






                                       6.