content: <PAGE>   1
                         
  As filed with the Securities and Exchange Commission on June 7, 1996. 
                                                       REGISTRATION NO. 333-
  - --------------------------------------------------------------------------------
  
                                    UNITED STATES
                         SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
  
                                      FORM S-8
  
               REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
  
                    ---------------------------------------------
  
                            CAMBRIDGE NEUROSCIENCE, INC.
               (Exact Name of Registrant as Specified in its Charter)
  
                  DELAWARE                              13-3319074
       (State or Other Jurisdiction of         (IRS Employer Identification No.)
        Incorporation or Organization)
  
           ONE KENDALL SQUARE, BUILDING 700, CAMBRIDGE MASSACHUSETTS 02139
                      (Address of Principal Executive Offices)
        
                    ---------------------------------------------
  
                             1991 EQUITY INCENTIVE PLAN
                              (Full Title of the Plan)
  
                                   ELKAN R. GAMZU
                        PRESIDENT AND CHIEF EXECUTIVE OFFICER
                            CAMBRIDGE NEUROSCIENCE, INC.
                            ONE KENDALL SQUARE, BLDG. 700
                           CAMBRIDGE, MASSACHUSETTS 02139
                                   (617) 225-0600
              (Name, Address and Telephone Number of Agent for Service)
  
                                   with copies to:
                                PETER WIRTH, ESQUIRE
                                 PALMER & DODGE LLP
                                  ONE BEACON STREET
                             BOSTON, MASSACHUSETTS 02108
                                   (617) 573-0100
  
                    ---------------------------------------------
  
                           CALCULATION OF REGISTRATION FEE
  
  <TABLE>
  <CAPTION>
  
  ==========================================================================================================
                                                     Proposed              Proposed
        Title of                                     Maximum               Maximum
       Securities               Amount               Offering              Aggregate             Amount of
          to be                 to be               Price Per              Offering            Registration
       Registered             Registered             Share (1)             Price (1)                Fee
  - ----------------------------------------------------------------------------------------------------------
  
     <S>                  <C>                         <C>                 <C>                   <C>  
      Common Stock,
     $.001 par value      500,000 shares (2)          $9.625              $4,812,500            $1,659.48
  ==========================================================================================================
  
  <FN>
  
  (1)  Estimated solely for the purpose of determining the  registration fee and computed  pursuant to Rule 
       457(h) and based on the average of the high and low sales prices on June 3, 1996, as reported in the 
       Nasdaq National Market System.
  (2)  This  Registration  Statement  registers an additional  500,000 shares of Common Stock under the 1991 
       Equity  Incentive  Plan. A total of 1,600,000  shares of Common Stock have previously been registered 
       under such plan (SEC File No. 33-42933 and File No. 33-76408).
  
  </TABLE>
  
                          Exhibit Index Appears at Page 4.
  
  <PAGE>   2
  
  
  
       The contents of the Registration Statements on Form S-8 of Cambridge
  NeuroScience, Inc. (the "Company"), as filed with the Securities and Exchange
  Commission on September 30, 1991 (Commission File No. 33-42933) and March 11,
  1994 (Commission File No. 33-76408), relating to the registration of a total of
  1,600,000 shares of the Company's Common Stock, $.001 par value per share (the
  "Common Stock"), authorized for issuance under the Company's 1991 Equity
  Incentive Plan (the "Plan"), are incorporated by reference in their entirety
  herein in accordance with General Instruction E to Form S-8. This Registration
  Statement provides for the registration of an additional 500,000 shares of the
  Company's Common Stock authorized for issuance under the Plan.
  
  
                                        -2-
  
  <PAGE>   3
  
  
                                     SIGNATURES
  
       Pursuant to the requirements of the Securities Act of 1933, the Registrant
  certifies that it has reasonable grounds to believe that it meets all of the
  requirements for filing on Form S-8 and has duly caused this Registration
  Statement to be signed on its behalf by the undersigned, thereunto duly
  authorized, in the City of Cambridge, Commonwealth of Massachusetts, on this 7th
  day of June, 1996. 
                              CAMBRIDGE NEUROSCIENCE, INC.
  
                                      By: /s/ Harry W. Wilcox, III
                                         -----------------------------
                                          Harry W. Wilcox, III
                                          Senior Vice President, Finance and
                                          Business Development, and
                                          Chief Financial Officer
  
                                  POWER OF ATTORNEY
  
       We, the undersigned Officers and Directors of Cambridge NeuroScience, Inc.,
  hereby severally constitute and appoint Elkan R. Gamzu, Harry W. Wilcox, III,
  Ross S. Gibson, William T. Whelan and Peter Wirth, and each of them singly, our
  true and lawful attorneys-in-fact, with full power to them in any and all
  capacities, to sign any amendments to this Registration Statement on Form S-8,
  including any post-effective amendments thereto, and to file the same, with
  exhibits thereto and other documents in connection therewith, with the
  Securities and Exchange Commission, hereby ratifying and confirming all that
  each of said attorneys-in-fact may do or cause to be done by virtue hereof.
  
  <TABLE>
  
       Pursuant to the requirements of the Securities Act of 1933, this
  Registration Statement has been signed below by the following persons in the
  capacities and on the dates indicated:
  <CAPTION>
  
         SIGNATURE                               TITLE                              DATE
         ---------                               -----                              ----
  
  <S>                                         <C>                                 <C>
  /s/ Elkan R. Gamzu                          President and                       May 31, 1996
  - ---------------------------                 Chief Executive Officer
  Elkan R. Gamzu                              (Principal Executive Officer)
                                              and Director                                    
                                
  
  /s/ Harry W. Wilcox, III                    Senior Vice President, Finance      May 31, 1996
  - ---------------------------                 and Business Development
  Harry W. Wilcox, III                        (Principal Financial
                                              and Accounting Officer)
                         
  
  /s/ Nancy S. Amer                           Director                            May 31, 1996
  - ---------------------------
  Nancy S. Amer
  
                                              Director                            May 31, 1996
  - ---------------------------
  Burkhard Blank
  
  /s/ Ira A. Jackson                          Director                            May 31, 1996
  - ---------------------------
  Ira A. Jackson
  
  /s/ S. Joshua Lewis                         Director                            May 31, 1996
  - ---------------------------
  S. Joshua Lewis
  
  /s/ Joseph B. Martin                        Director                            May 31, 1996
  - ---------------------------
  Joseph B. Martin
  
  /s/ Paul C. O'Brien                         Director                            May 31, 1996
  - ---------------------------
  Paul C. O'Brien
  
  /s/ Peter Stalker, III                      Director                            May 31,  1996
  - ----------------------------
  Peter Stalker, III
  </TABLE>
  
                                        -3-
  
  <PAGE>   4
  
  
                                    EXHIBIT INDEX
  
  <TABLE>
  <CAPTION>
  
  
  EXHIBIT                                                                              PAGE
  NUMBER                                DESCRIPTION                                   NUMBER
  - ------                                -----------                                   ------
  
  <S>          <C>                                                                      <C>
  5            Opinion of Palmer & Dodge LLP as to the legality of the securities       5
               registered hereunder.
  
  23.1         Consent of Ernst & Young LLP, independent auditors.                      6
  
  23.2         Consent of Palmer & Dodge LLP (contained in Opinion of                   5
               Palmer & Dodge LLP filed as Exhibit 5).
  
  24           Power of Attorney (set forth on the Signature Page to                    3
               this Registration Statement).
  
  99.1         Cambridge NeuroScience, Inc. 1991 Equity Incentive Plan, as amended.     7
  
  </TABLE>
  
                                        -4-
metadata_documents: [{"type": "S-8", "sequence": "1", "description": "CAMBRIDGE NEUROSCIENCE, INC.", "secsgml_size_bytes": 9440}]
metadata_filer: {"company-data": {"conformed-name": "CAMBRIDGE NEUROSCIENCE INC", "cik": "0000874384", "assigned-sic": "2834", "irs-number": "133319074", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-05431", "film-number": "96578016"}, "business-address": {"street1": "ONE KENDALL SQ BUILD 700", "city": "CAMBRIDGE", "state": "MA", "zip": "02139", "phone": "6172250600"}, "mail-address": {"street1": "ONE KENDALL SQ", "street2": "BLDG 700", "city": "CAMBRIDGE", "state": "MA", "zip": "02139"}, "former-company": {"former-conformed-name": "CAMBRIDGE NEUROSCIENCE RESEARCH INC", "date-changed": "19600201"}}
text: 1
                         
  As filed with the Securities and Exchange Commission on June 7, 1996. 
                                                       REGISTRATION NO. 333-
  - --------------------------------------------------------------------------------
  
                                    UNITED STATES
                         SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
  
                                      FORM S-8
  
               REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
  
                    ---------------------------------------------
  
                            CAMBRIDGE NEUROSCIENCE, INC.
               (Exact Name of Registrant as Specified in its Charter)
  
                  DELAWARE                              13-3319074
       (State or Other Jurisdiction of         (IRS Employer Identification No.)
        Incorporation or Organization)
  
           ONE KENDALL SQUARE, BUILDING 700, CAMBRIDGE MASSACHUSETTS 02139
                      (Address of Principal Executive Offices)
        
                    ---------------------------------------------
  
                             1991 EQUITY INCENTIVE PLAN
                              (Full Title of the Plan)
  
                                   ELKAN R. GAMZU
                        PRESIDENT AND CHIEF EXECUTIVE OFFICER
                            CAMBRIDGE NEUROSCIENCE, INC.
                            ONE KENDALL SQUARE, BLDG. 700
                           CAMBRIDGE, MASSACHUSETTS 02139
                                   (617) 225-0600
              (Name, Address and Telephone Number of Agent for Service)
  
                                   with copies to:
                                PETER WIRTH, ESQUIRE
                                 PALMER & DODGE LLP
                                  ONE BEACON STREET
                             BOSTON, MASSACHUSETTS 02108
                                   (617) 573-0100
  
                    ---------------------------------------------
  
                           CALCULATION OF REGISTRATION FEE
  ==========================================================================================================
                                                     Proposed              Proposed
        Title of                                     Maximum               Maximum
       Securities               Amount               Offering              Aggregate             Amount of
          to be                 to be               Price Per              Offering            Registration
       Registered             Registered             Share (1)             Price (1)                Fee
  - ----------------------------------------------------------------------------------------------------------
  Common Stock,
     $.001 par value      500,000 shares (2)          $9.625              $4,812,500            $1,659.48
  ==========================================================================================================
  (1)  Estimated solely for the purpose of determining the  registration fee and computed  pursuant to Rule 
       457(h) and based on the average of the high and low sales prices on June 3, 1996, as reported in the 
       Nasdaq National Market System.
  (2)  This  Registration  Statement  registers an additional  500,000 shares of Common Stock under the 1991 
       Equity  Incentive  Plan. A total of 1,600,000  shares of Common Stock have previously been registered 
       under such plan (SEC File No. 33-42933 and File No. 33-76408).
  Exhibit Index Appears at Page 4.
  2
  
       The contents of the Registration Statements on Form S-8 of Cambridge
  NeuroScience, Inc. (the "Company"), as filed with the Securities and Exchange
  Commission on September 30, 1991 (Commission File No. 33-42933) and March 11,
  1994 (Commission File No. 33-76408), relating to the registration of a total of
  1,600,000 shares of the Company's Common Stock, $.001 par value per share (the
  "Common Stock"), authorized for issuance under the Company's 1991 Equity
  Incentive Plan (the "Plan"), are incorporated by reference in their entirety
  herein in accordance with General Instruction E to Form S-8. This Registration
  Statement provides for the registration of an additional 500,000 shares of the
  Company's Common Stock authorized for issuance under the Plan.
  
                                        -2-
  3
  
                                     SIGNATURES
  
       Pursuant to the requirements of the Securities Act of 1933, the Registrant
  certifies that it has reasonable grounds to believe that it meets all of the
  requirements for filing on Form S-8 and has duly caused this Registration
  Statement to be signed on its behalf by the undersigned, thereunto duly
  authorized, in the City of Cambridge, Commonwealth of Massachusetts, on this 7th
  day of June, 1996. 
                              CAMBRIDGE NEUROSCIENCE, INC.
  
                                      By: /s/ Harry W. Wilcox, III
                                         -----------------------------
                                          Harry W. Wilcox, III
                                          Senior Vice President, Finance and
                                          Business Development, and
                                          Chief Financial Officer
  
                                  POWER OF ATTORNEY
  
       We, the undersigned Officers and Directors of Cambridge NeuroScience, Inc.,
  hereby severally constitute and appoint Elkan R. Gamzu, Harry W. Wilcox, III,
  Ross S. Gibson, William T. Whelan and Peter Wirth, and each of them singly, our
  true and lawful attorneys-in-fact, with full power to them in any and all
  capacities, to sign any amendments to this Registration Statement on Form S-8,
  including any post-effective amendments thereto, and to file the same, with
  exhibits thereto and other documents in connection therewith, with the
  Securities and Exchange Commission, hereby ratifying and confirming all that
  each of said attorneys-in-fact may do or cause to be done by virtue hereof.
  
       Pursuant to the requirements of the Securities Act of 1933, this
  Registration Statement has been signed below by the following persons in the
  capacities and on the dates indicated:
  SIGNATURE                               TITLE                              DATE
         ---------                               -----                              ----
  /s/ Elkan R. Gamzu                          President and                       May 31, 1996
  - ---------------------------                 Chief Executive Officer
  Elkan R. Gamzu                              (Principal Executive Officer)
                                              and Director                                    
                                
  
  /s/ Harry W. Wilcox, III                    Senior Vice President, Finance      May 31, 1996
  - ---------------------------                 and Business Development
  Harry W. Wilcox, III                        (Principal Financial
                                              and Accounting Officer)
                         
  
  /s/ Nancy S. Amer                           Director                            May 31, 1996
  - ---------------------------
  Nancy S. Amer
  
                                              Director                            May 31, 1996
  - ---------------------------
  Burkhard Blank
  
  /s/ Ira A. Jackson                          Director                            May 31, 1996
  - ---------------------------
  Ira A. Jackson
  
  /s/ S. Joshua Lewis                         Director                            May 31, 1996
  - ---------------------------
  S. Joshua Lewis
  
  /s/ Joseph B. Martin                        Director                            May 31, 1996
  - ---------------------------
  Joseph B. Martin
  
  /s/ Paul C. O'Brien                         Director                            May 31, 1996
  - ---------------------------
  Paul C. O'Brien
  
  /s/ Peter Stalker, III                      Director                            May 31,  1996
  - ----------------------------
  Peter Stalker, III
  -3-
  4
  
                                    EXHIBIT INDEX
  EXHIBIT                                                                              PAGE
  NUMBER                                DESCRIPTION                                   NUMBER
  - ------                                -----------                                   ------
  5            Opinion of Palmer & Dodge LLP as to the legality of the securities       5
               registered hereunder.
  
  23.1         Consent of Ernst & Young LLP, independent auditors.                      6
  
  23.2         Consent of Palmer & Dodge LLP (contained in Opinion of                   5
               Palmer & Dodge LLP filed as Exhibit 5).
  
  24           Power of Attorney (set forth on the Signature Page to                    3
               this Registration Statement).
  
  99.1         Cambridge NeuroScience, Inc. 1991 Equity Incentive Plan, as amended.     7
  -4-