content: <PAGE>   1
  As filed with the Securities and Exchange Commission on May 24, 2001.
  
                                                     Registration No. 333-________
  
  
                         SECURITIES AND EXCHANGE COMMISSION
                                WASHINGTON, DC. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                                  SIPEX Corporation
               (Exact name of registrant as specified in its charter)
  
                  Massachusetts                            04-6135748
         (State or other jurisdiction of                (I.R.S. Employer
         incorporation or organization)               Identification No.)
  
                                  22 Linnell Circle
                                 Billerica, MA 01821
                                   (978) 667-8700
                 (Address of Principal Executive Offices) (Zip Code)
                            -----------------------------
  
                        2000 Non-Qualified Stock Option Plan
                              (Full title of the plan)
  
                            -----------------------------
  
                                  James E. Donegan
                               Chief Executive Officer
                                  SIPEX Corporation
                                  22 Linnell Circle
                                 Billerica, MA 01821
                                   (978) 667-8700
             (Name and address including zip code and telephone number,
                     including area code, of agent for service)
  
                            -----------------------------
  
                                     Copies to:
  
                               Kenneth J. Gordon, Esq.
                           TESTA, HURWITZ & THIBEAULT, LLP
                                   125 High Street
                             Boston, Massachusetts 02110
                                   (617) 248-7000
  <PAGE>   2
                                        -2-
  
  
                           CALCULATION OF REGISTRATION FEE
  
  
  <TABLE>
  <CAPTION>
                                                                       Proposed
                                                                        maximum         Proposed maximum
             Title of securities                Amount to be           offering            aggregate                Amount of
               to be registered                 registered(1)       price per share      offering price         registration fee
  <S>                                           <C>                 <C>                 <C>                     <C>
  2000 NON-QUALIFIED STOCK OPTION PLAN
  Common Stock, par value $.01 per share           494,770             $12.688(2)      $ 6,277,641.76(2)          $1,569.41(2)
                                                    55,000             $ 6.870(2)      $   377,850.00(2)          $   94.46
                                                   450,230             $12.99 (3)        5,848,487.70(3)          $1,462.12(3)
  
  NON-PLAN OPTIONS
  Common Stock, par value                          710,000             $12.688(2)      $ 9,008,480.00(2)          $2,252.12(2)
  $.01 per share                                    55,000             $ 6.870(2)      $   377,850.00(2)          $   94.46
                                                 ---------                             --------------             ---------
  TOTAL                                          1,765,000                             $21,890,309.46             $5,472.57
  </TABLE>
  
  
  (1)        Plus such additional shares as may be required pursuant to the plan
             in the event of a stock dividend, split-up of shares,
             recapitalization or other similar change in the Common Stock.
  
  (2)        Such shares are issuable upon exercise of outstanding options with
             fixed exercise prices. Pursuant to Rule 457(h)(1) of Regulation C,
             the aggregate offering price and the fee have been computed upon the
             basis of the price at which the options may be exercised. The
             offering price per share set forth for such shares is the exercise
             price per share at which such options are exercisable.
  
  (3)        Pursuant to Rule 457(c) and (h)(1) of Regulation C of the Securities
             Act, the price of $12.99 per share, is the average of the high and
             low prices of the Common Stock as reported on The Nasdaq National
             Market on May 22, 2001 and is set forth solely for purposes of
             calculating the filing fee for those shares without a fixed exercise
             price.
  <PAGE>   3
                                        -3-
  
  
             This Registration Statement registers additional securities of the
  same class as other securities for which (i) Registration Statement No.
  333-06123 on Form S-8 as filed with the Securities and Exchange Commission on
  June 17, 1996 (relating to the Registrant's 1988 Non-Statutory Stock Option
  Plan, 1991 Non-Statutory Stock Option Plan, 1993 Stock Option and Incentive
  Plan, 1994 Stock Option and Incentive Plan, 1996 Incentive Stock Option Plan,
  1996 Non-Employee Director Stock Option Plan and 1996 Employee Stock Purchase
  Plan) is effective, (ii) Registration Statement No. 333-32329 on Form S-8 as
  filed with the Securities and Exchange Commission on July 29, 1997 relating to
  the Registrant's 1997 Stock Option Plan is effective, and (iii) Registration
  Statement No. 333-31410 on Form S-8 as filed with the Securities and Exchange
  Commission on March 1, 2000 relating to the Registrant's 1999 Stock Option Plan
  is effective. Pursuant to General Instruction E to Form S-8, the contents of the
  above-listed Registration Statements are hereby incorporated by reference.
  
                                       PART I
  
                INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
  ITEM 1.    PLAN INFORMATION.
  
             The documents containing the information specified in this Item 1
  will be sent or given to employees, directors or others as specified by Rule
  428(b)(1). In accordance with the rules and regulations of the Securities and
  Exchange Commission (the "Commission") and the instructions to Form S-8, such
  documents are not being filed with the Commission either as part of this
  Registration Statement or as prospectuses or prospectus supplements pursuant to
  Rule 424.
  
  ITEM 2.    REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION.
  
             The documents containing the information specified in this Item 2
  will be sent or given to employees as specified by Rule 428(b)(1). In accordance
  with the rules and regulations of the Commission and the instructions to Form
  S-8, such documents are not being filed with the Commission either as part of
  the Registration Statement or as prospectuses or prospectus supplements pursuant
  to Rule 424.
  
                                       PART II
  
                 INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
  
  ITEM 3.    INCORPORATION OF DOCUMENTS BY REFERENCE.
  
             The following documents filed by SIPEX Corporation (the "Registrant")
  with the Commission pursuant to the Securities Exchange Act of 1934, as amended
  (the "Exchange Act"), are incorporated in this Registration Statement by
  reference as of their respective dates:
  
             (a)        The Registrant's Annual Report on Form 10-K for the fiscal
                        year ended December 31, 2000, filed with the Commission on
                        March 23, 2001;
  
             (b)        The Registrant's Quarterly Report on From 10-Q for the
                        quarter ended March 31, 2001;
  
             (c)        The section entitled "Description of Registrant's
                        Securities to be Registered" contained in the Registrant's
                        registration statement on Form 8-A filed with the
                        Commission on March 1, 1996 pursuant to Section 12(g) of
                        the Exchange Act and incorporating by reference the
                        information contained in the Registrant's Registration
                        Statement on Form S-1 (SEC File No. 333-14639) initially
                        filed with the Commission on March 1, 1996.
  
             All documents subsequently filed with the Commission by the
  Registrant pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act,
  prior to the filing of a post-effective amendment which indicates that all
  securities offered herein have been sold or which deregisters all securities
  then remaining unsold, shall be deemed to be incorporated by reference in this
  Registration Statement and to be a part hereof from the date of filing of such
  documents.
  <PAGE>   4
                                        -4-
  
  ITEM 4. DESCRIPTION OF SECURITIES.
  
  Not applicable.
  
  ITEM 5. INTEREST OF NAMED EXPERTS AND COUNSEL
  
  Not applicable.
  
  ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
  
             Massachusetts General Laws Chapter 156B, Section 67 provides that a
  corporation may indemnify its directors and officers to the extent specified in
  or authorized by (i) the articles of organization, (ii) a by-law adopted by the
  shareholders, or (iii) a vote adopted by the holders of a majority of the shares
  of stock entitled to vote on the election of directors. In all instances, the
  extent to which a corporation provides indemnification to its directors and
  officers under Section 67 is optional. Massachusetts General Laws Chapter 156B,
  Section 67 forbids the indemnification of any person with respect to any matter
  to which he shall have been adjudicated in any proceeding not to have acted in
  good faith in the reasonable belief that his action was in the best interest of
  the corporation.
  
             The Company's Restated By-Laws indemnifies the directors and officers
  against liabilities arising out of legal proceedings brought against them by
  reason of their status as directors and officers or by reason of their agreeing
  to serve, at the request of the Company, as a director or officer of another
  organization. Under the Restated By-Laws, each director and officer shall be
  indemnified by the Company for all costs and expenses (including attorneys'
  fees), judgments, liabilities and amounts paid in settlement of such
  proceedings, even if he is not successful on the merits, if he acted in good
  faith in the reasonable belief that his action was in the best interest of the
  Company. The Board of Directors may authorize advancing litigation expenses to a
  director or officer at his request upon receipt of an undertaking by such
  director or officer to repay such expenses if it is ultimately determined that
  he is not entitled to indemnification for such expense. The Restated By-Laws
  provide that the directors and officers of the Company shall be indemnified by
  the Company to the fullest extent authorized by Massachusetts Law, as it now
  exists or may in the future be amended. In addition, the Restated Articles
  provide that the directors of the Company will not be personally liable for
  monetary damages to the Company for breaches of their fiduciary duty as
  directors, unless they violated their duty of loyalty to the Company or its
  shareholders, acted in bad faith, knowingly or intentionally violated the law,
  authorized illegal dividends or redemptions or derived an improper personal
  benefit from their action as directors.
  
             The Company has entered into separate indemnification agreements with
  each of its directors and executive officers, whereby the Company agreed, among
  other things, (i) to indemnify them to the fullest extent permitted by the
  Business Corporation Law of the Commonwealth of Massachusetts, subject to
  specified limitations, against certain liabilities actually and reasonably
  incurred by them in any proceedings in which they are a party that may arise by
  reason of their status as directors, officers, employees or agents or may arise
  by reason of their serving as such at the request of the Company for another
  entity and (ii) to advance their expenses incurred as a result of any proceeding
  against them as to which they could be indemnified. The Company intends to enter
  into similar separate indemnification agreements with any directors or officers
  who may join the Company in the future.
  
  ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.
  
  Not applicable.
  <PAGE>   5
                                        -5-
  
  
  ITEM 8.  EXHIBITS.
  
  <TABLE>
  <CAPTION>
   Exhibit No.                      Description of Exhibit
  <S>            <C>
         4.1*    Restated Articles of Organization of the Registrant (filed as
                 Exhibit 3.2 to the Registrant's Registration Statement on Form
                 S-1, File No. 333-1328, and incorporated herein by reference).
  
         4.2*    Restated By-Laws of the Registrant (filed as Exhibit 3.3 to the
                 Registrant's Registration Statement on Form S-1, File No.
                 333-1328, and incorporated herein by reference).
  
         4.3     SIPEX Corporation 2000 Non-Qualified Stock Option Plan.
  
         4.4     Form of Non-Qualified Stock Option Agreement (Plan).
  
         4.5     Form of Non-Qualified Stock Option Agreement (Non-Plan).
  
         4.6     Non-Qualified Stock Option Agreement dated January 16, 2001 by
                 and between the Registrant and Bruce Diamond.
  
         5.1     Opinion of Testa, Hurwitz & Thibeault, LLP.
  
        23.1     Consent of Testa, Hurwitz & Thibeault, LLP (contained in its
                 opinion as Exhibit 5.1).
  
        23.2     Consent of KPMG, LLP.
  
        23.3     Consent of Sallmann, Yang & Alameda.
  
        24.1     Power of Attorney (included as part of the signature page of this
                 Registration Statement).
  </TABLE>
  
  *Incorporated by reference to Exhibits to the Registrant's Registration
  Statement on Form S-1, No. 333-1328
  
  
  ITEM 9.    UNDERTAKINGS.
  
             (a)        The undersigned Registrant hereby undertakes:
  
                        (1)        To file, during any period in which offers or
                                   sales are being made, a post-effective
                                   amendment to this Registration Statement:
  
                                   (i)        To include any prospectus required
                                              by Section 10(a)(3) of the
                                              Securities Act of 1933;
  
                                   (ii)       To reflect in the prospectus any
                                              facts or events arising after the
                                              effective date of the Registration
                                              Statement (or the most recent
                                              post-effective amendment thereof)
                                              which, individually or in the
                                              aggregate, represent a fundamental
                                              change in the information set forth
                                              in the Registration Statement; and
  <PAGE>   6
                                        -6-
  
  
                                   (iii)      To include any material information
                                              with respect to the plan of
                                              distribution not previously
                                              disclosed in the Registration
                                              Statement or any material change to
                                              such information in the Registration
                                              Statement;
  
                                   provided, however, that paragraphs (a)(1)(i)
                                   and (a)(1)(ii) do not apply if the information
                                   required to be included in a post-effective
                                   amendment by those paragraphs is contained in
                                   periodic reports filed with or furnished to the
                                   Commission by the Registrant pursuant to
                                   Section 13 or Section 15(d) of the Securities
                                   Exchange Act of 1934 that are incorporated by
                                   reference in the Registration Statement.
  
                        (2)        That, for the purpose of determining any
                                   liability under the Securities Act of 1933,
                                   each such post-effective amendment shall be
                                   deemed to be a new registration statement
                                   relating to the securities offered therein, and
                                   the offering of such securities at that time
                                   shall be deemed to be the initial bona fide
                                   offering thereof.
  
                        (3)        To remove from registration by means of a
                                   post-effective amendment any of the securities
                                   being registered which remain unsold at the
                                   termination of the offering.
  
             (b)        The undersigned Registrant hereby undertakes that, for
                        purposes of determining any liability under the Securities
                        Act of 1933, each filing of the Registrant's annual report
                        pursuant to Section 13(a) or Section 15(d) of the
                        Securities Exchange Act of 1934 (and, where applicable,
                        each filing of any employee benefit plan's annual report
                        pursuant to Section 15(d) of the Securities Exchange Act
                        of 1934) that is incorporated by reference in the
                        Registration Statement shall be deemed to be a new
                        registration statement relating to the securities offered
                        therein, and the offering of such securities at that time
                        shall be deemed to be the initial bona fide offering
                        thereof.
  
             (c)        Insofar as indemnification for liabilities arising under
                        the Securities Act of 1933 may be permitted to directors,
                        officers and controlling persons of the Registrant
                        pursuant to the foregoing provisions, or otherwise, the
                        Registrant has been advised that in the opinion of the
                        Securities and Exchange Commission such indemnification is
                        against public policy as expressed in the Act and is,
                        therefore, unenforceable. In the event that a claim for
                        indemnification against such liabilities (other than the
                        payment by the Registrant of expenses incurred or paid by
                        a director, officer or controlling person of the
                        Registrant in the successful defense of any action, suit
                        or proceeding) is asserted by such director, officer or
                        controlling person in connection with the securities being
                        registered, the Registrant will, unless in the opinion of
                        its counsel the matter has been settled by controlling
                        precedent, submit to a court of appropriate jurisdiction
                        the question whether such indemnification by it is against
                        public policy as expressed in the Act and will be governed
                        by the final adjudication of such issue.
  <PAGE>   7
                                        -7-
  
  
                                     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 Billerica, the Commonwealth of Massachusetts, on this
  24th day of May, 2001.
  
                                        SIPEX CORPORATION
  
                                        By:   /s/  James E. Donegan
                                             ------------------------------------
                                             James E. Donegan
                                             Chairman of the Board of Directors
                                             and Chief Executive Officer
  
                                  POWER OF ATTORNEY
  
             EACH SUCH PERSON WHOSE SIGNATURE appears below constitutes and
  appoints, jointly and severally, James E. Donegan and Frank R. DiPietro and each
  of them, with full power to act without the other, his true and lawful
  attorney-in-fact and agent, with the power of substitution and resubstitution,
  for him and in his name, place and stead, in any and all capacities, to sign any
  amendments to this Registration Statement on Form S-8 (including post-effective
  amendments) and to file the same, with all exhibits thereto, and other documents
  in connection therewith, with the Securities and Exchange Commission, hereby
  ratifying and confirming all that said attorney-in-fact, or his or her
  substitute or substitutes, 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 by the following persons in the
  capacities and on the date indicated.
  
  <TABLE>
  <CAPTION>
                    SIGNATURE                                        TITLE                                         DATE
  <S>                                             <C>                                                          <C>
    /s/  James E. Donegan                         Chairman of the Board of Directors, Chief                    May 24, 2001
    --------------------------------------        Executive Officer and Director
    James E. Donegan
  
    /s/  Frank R. DiPietro                        Executive Vice President, Finance, Chief                     May 24, 2001
    --------------------------------------        Financial Officer, Treasurer (principal
    Frank R. DiPietro                             financial officer and accounting officer)
                                                  and Clerk
  
    /s/  Manfred Loeb                             Director                                                     May 24, 2001
    --------------------------------------
    Manfred Loeb
  
    /s/  Lionel H. Olmer                          Director                                                     May 24, 2001
    --------------------------------------
    Lionel H. Olmer
  
    /s/  John L. Sprague                          Director                                                     May 24, 2001
    --------------------------------------
    John L. Sprague
  
    /s/  Doug McBunnie                            Director                                                     May 24, 2001
    --------------------------------------
    Doug McBurnie
  
    /s/  Willy Sansen                             Director                                                     May 24, 2001
    --------------------------------------
    Willy Sansen
  </TABLE>
  <PAGE>   8
                                        -8-
  
  
  <TABLE>
  <CAPTION>
          Exhibit                     Description of Exhibit
  <S>                 <C>
            4.1*      Restated Articles of Organization of the Registrant.
  
            4.2*      Restated By-Laws of the Registrant.
  
            4.3       SIPEX Corporation 2000 Non-Qualified Stock Option
                      Plan.
  
            4.4       Form of Non-Qualified Stock Option Agreement (Plan).
  
            4.5       Form of Non-Qualified Stock Option Agreement
                      (Non-Plan).
  
            4.6       Non-Qualified Stock Option Agreement dated January 16,
                      2001 by and between the Registrant and Bruce Diamond.
  
            5.1       Opinion of Testa, Hurwitz & Thibeault, LLP.
  
            23.1      Consent of Testa, Hurwitz & Thibeault, LLP (contained
                      in its opinion as Exhibit 5.1).
  
            23.2      Consent of  KPMG, LLP.
  
            23.3      Consent of Sallmann, Yang & Alameda.
  
            24.1      Power of Attorney (included as part of the signature
                      page of this Registration Statement).
  </TABLE>
  
  *Incorporated by reference to Exhibits to the Registrant's Registration
  Statement on Form S-1, No. 333-1328
metadata_documents: [{"type": "S-8", "sequence": "1", "filename": "b39547scs-8.txt", "description": "SIPEX CORPORATION", "secsgml_size_bytes": 24731}]
metadata_filer: {"company-data": {"conformed-name": "SIPEX CORP", "cik": "0001007800", "assigned-sic": "3674", "irs-number": "046135748", "state-of-incorporation": "MA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-61560", "film-number": "1647372"}, "business-address": {"street1": "22 LINNELL CIRCLE", "city": "BILLERICA", "state": "MA", "zip": "01821", "phone": "9786678700"}, "mail-address": {"street1": "22 LINNELL CIRCLE", "city": "BILLERICA", "state": "MA", "zip": "01821"}}
text: 1
  As filed with the Securities and Exchange Commission on May 24, 2001.
  
                                                     Registration No. 333-________
  
                         SECURITIES AND EXCHANGE COMMISSION
                                WASHINGTON, DC. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                                  SIPEX Corporation
               (Exact name of registrant as specified in its charter)
  
                  Massachusetts                            04-6135748
         (State or other jurisdiction of                (I.R.S. Employer
         incorporation or organization)               Identification No.)
  
                                  22 Linnell Circle
                                 Billerica, MA 01821
                                   (978) 667-8700
                 (Address of Principal Executive Offices) (Zip Code)
                            -----------------------------
  
                        2000 Non-Qualified Stock Option Plan
                              (Full title of the plan)
  
                            -----------------------------
  
                                  James E. Donegan
                               Chief Executive Officer
                                  SIPEX Corporation
                                  22 Linnell Circle
                                 Billerica, MA 01821
                                   (978) 667-8700
             (Name and address including zip code and telephone number,
                     including area code, of agent for service)
  
                            -----------------------------
  
                                     Copies to:
  
                               Kenneth J. Gordon, Esq.
                           TESTA, HURWITZ & THIBEAULT, LLP
                                   125 High Street
                             Boston, Massachusetts 02110
                                   (617) 248-7000
  2
                                        -2-
  
                           CALCULATION OF REGISTRATION FEE
  Proposed
                                                                        maximum         Proposed maximum
             Title of securities                Amount to be           offering            aggregate                Amount of
               to be registered                 registered(1)       price per share      offering price         registration fee
  2000 NON-QUALIFIED STOCK OPTION PLAN
  Common Stock, par value $.01 per share           494,770             $12.688(2)      $ 6,277,641.76(2)          $1,569.41(2)
                                                    55,000             $ 6.870(2)      $   377,850.00(2)          $   94.46
                                                   450,230             $12.99 (3)        5,848,487.70(3)          $1,462.12(3)
  
  NON-PLAN OPTIONS
  Common Stock, par value                          710,000             $12.688(2)      $ 9,008,480.00(2)          $2,252.12(2)
  $.01 per share                                    55,000             $ 6.870(2)      $   377,850.00(2)          $   94.46
                                                 ---------                             --------------             ---------
  TOTAL                                          1,765,000                             $21,890,309.46             $5,472.57
  (1)        Plus such additional shares as may be required pursuant to the plan
             in the event of a stock dividend, split-up of shares,
             recapitalization or other similar change in the Common Stock.
  
  (2)        Such shares are issuable upon exercise of outstanding options with
             fixed exercise prices. Pursuant to Rule 457(h)(1) of Regulation C,
             the aggregate offering price and the fee have been computed upon the
             basis of the price at which the options may be exercised. The
             offering price per share set forth for such shares is the exercise
             price per share at which such options are exercisable.
  
  (3)        Pursuant to Rule 457(c) and (h)(1) of Regulation C of the Securities
             Act, the price of $12.99 per share, is the average of the high and
             low prices of the Common Stock as reported on The Nasdaq National
             Market on May 22, 2001 and is set forth solely for purposes of
             calculating the filing fee for those shares without a fixed exercise
             price.
  3
                                        -3-
  
             This Registration Statement registers additional securities of the
  same class as other securities for which (i) Registration Statement No.
  333-06123 on Form S-8 as filed with the Securities and Exchange Commission on
  June 17, 1996 (relating to the Registrant's 1988 Non-Statutory Stock Option
  Plan, 1991 Non-Statutory Stock Option Plan, 1993 Stock Option and Incentive
  Plan, 1994 Stock Option and Incentive Plan, 1996 Incentive Stock Option Plan,
  1996 Non-Employee Director Stock Option Plan and 1996 Employee Stock Purchase
  Plan) is effective, (ii) Registration Statement No. 333-32329 on Form S-8 as
  filed with the Securities and Exchange Commission on July 29, 1997 relating to
  the Registrant's 1997 Stock Option Plan is effective, and (iii) Registration
  Statement No. 333-31410 on Form S-8 as filed with the Securities and Exchange
  Commission on March 1, 2000 relating to the Registrant's 1999 Stock Option Plan
  is effective. Pursuant to General Instruction E to Form S-8, the contents of the
  above-listed Registration Statements are hereby incorporated by reference.
  
                                       PART I
  
                INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
  ITEM 1.    PLAN INFORMATION.
  
             The documents containing the information specified in this Item 1
  will be sent or given to employees, directors or others as specified by Rule
  428(b)(1). In accordance with the rules and regulations of the Securities and
  Exchange Commission (the "Commission") and the instructions to Form S-8, such
  documents are not being filed with the Commission either as part of this
  Registration Statement or as prospectuses or prospectus supplements pursuant to
  Rule 424.
  
  ITEM 2.    REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION.
  
             The documents containing the information specified in this Item 2
  will be sent or given to employees as specified by Rule 428(b)(1). In accordance
  with the rules and regulations of the Commission and the instructions to Form
  S-8, such documents are not being filed with the Commission either as part of
  the Registration Statement or as prospectuses or prospectus supplements pursuant
  to Rule 424.
  
                                       PART II
  
                 INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
  
  ITEM 3.    INCORPORATION OF DOCUMENTS BY REFERENCE.
  
             The following documents filed by SIPEX Corporation (the "Registrant")
  with the Commission pursuant to the Securities Exchange Act of 1934, as amended
  (the "Exchange Act"), are incorporated in this Registration Statement by
  reference as of their respective dates:
  
             (a)        The Registrant's Annual Report on Form 10-K for the fiscal
                        year ended December 31, 2000, filed with the Commission on
                        March 23, 2001;
  
             (b)        The Registrant's Quarterly Report on From 10-Q for the
                        quarter ended March 31, 2001;
  
             (c)        The section entitled "Description of Registrant's
                        Securities to be Registered" contained in the Registrant's
                        registration statement on Form 8-A filed with the
                        Commission on March 1, 1996 pursuant to Section 12(g) of
                        the Exchange Act and incorporating by reference the
                        information contained in the Registrant's Registration
                        Statement on Form S-1 (SEC File No. 333-14639) initially
                        filed with the Commission on March 1, 1996.
  
             All documents subsequently filed with the Commission by the
  Registrant pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act,
  prior to the filing of a post-effective amendment which indicates that all
  securities offered herein have been sold or which deregisters all securities
  then remaining unsold, shall be deemed to be incorporated by reference in this
  Registration Statement and to be a part hereof from the date of filing of such
  documents.
  4
                                        -4-
  
  ITEM 4. DESCRIPTION OF SECURITIES.
  
  Not applicable.
  
  ITEM 5. INTEREST OF NAMED EXPERTS AND COUNSEL
  
  Not applicable.
  
  ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
  
             Massachusetts General Laws Chapter 156B, Section 67 provides that a
  corporation may indemnify its directors and officers to the extent specified in
  or authorized by (i) the articles of organization, (ii) a by-law adopted by the
  shareholders, or (iii) a vote adopted by the holders of a majority of the shares
  of stock entitled to vote on the election of directors. In all instances, the
  extent to which a corporation provides indemnification to its directors and
  officers under Section 67 is optional. Massachusetts General Laws Chapter 156B,
  Section 67 forbids the indemnification of any person with respect to any matter
  to which he shall have been adjudicated in any proceeding not to have acted in
  good faith in the reasonable belief that his action was in the best interest of
  the corporation.
  
             The Company's Restated By-Laws indemnifies the directors and officers
  against liabilities arising out of legal proceedings brought against them by
  reason of their status as directors and officers or by reason of their agreeing
  to serve, at the request of the Company, as a director or officer of another
  organization. Under the Restated By-Laws, each director and officer shall be
  indemnified by the Company for all costs and expenses (including attorneys'
  fees), judgments, liabilities and amounts paid in settlement of such
  proceedings, even if he is not successful on the merits, if he acted in good
  faith in the reasonable belief that his action was in the best interest of the
  Company. The Board of Directors may authorize advancing litigation expenses to a
  director or officer at his request upon receipt of an undertaking by such
  director or officer to repay such expenses if it is ultimately determined that
  he is not entitled to indemnification for such expense. The Restated By-Laws
  provide that the directors and officers of the Company shall be indemnified by
  the Company to the fullest extent authorized by Massachusetts Law, as it now
  exists or may in the future be amended. In addition, the Restated Articles
  provide that the directors of the Company will not be personally liable for
  monetary damages to the Company for breaches of their fiduciary duty as
  directors, unless they violated their duty of loyalty to the Company or its
  shareholders, acted in bad faith, knowingly or intentionally violated the law,
  authorized illegal dividends or redemptions or derived an improper personal
  benefit from their action as directors.
  
             The Company has entered into separate indemnification agreements with
  each of its directors and executive officers, whereby the Company agreed, among
  other things, (i) to indemnify them to the fullest extent permitted by the
  Business Corporation Law of the Commonwealth of Massachusetts, subject to
  specified limitations, against certain liabilities actually and reasonably
  incurred by them in any proceedings in which they are a party that may arise by
  reason of their status as directors, officers, employees or agents or may arise
  by reason of their serving as such at the request of the Company for another
  entity and (ii) to advance their expenses incurred as a result of any proceeding
  against them as to which they could be indemnified. The Company intends to enter
  into similar separate indemnification agreements with any directors or officers
  who may join the Company in the future.
  
  ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.
  
  Not applicable.
  5
                                        -5-
  
  ITEM 8.  EXHIBITS.
  Exhibit No.                      Description of Exhibit
  4.1*    Restated Articles of Organization of the Registrant (filed as
                 Exhibit 3.2 to the Registrant's Registration Statement on Form
                 S-1, File No. 333-1328, and incorporated herein by reference).
  
         4.2*    Restated By-Laws of the Registrant (filed as Exhibit 3.3 to the
                 Registrant's Registration Statement on Form S-1, File No.
                 333-1328, and incorporated herein by reference).
  
         4.3     SIPEX Corporation 2000 Non-Qualified Stock Option Plan.
  
         4.4     Form of Non-Qualified Stock Option Agreement (Plan).
  
         4.5     Form of Non-Qualified Stock Option Agreement (Non-Plan).
  
         4.6     Non-Qualified Stock Option Agreement dated January 16, 2001 by
                 and between the Registrant and Bruce Diamond.
  
         5.1     Opinion of Testa, Hurwitz & Thibeault, LLP.
  
        23.1     Consent of Testa, Hurwitz & Thibeault, LLP (contained in its
                 opinion as Exhibit 5.1).
  
        23.2     Consent of KPMG, LLP.
  
        23.3     Consent of Sallmann, Yang & Alameda.
  
        24.1     Power of Attorney (included as part of the signature page of this
                 Registration Statement).
  *Incorporated by reference to Exhibits to the Registrant's Registration
  Statement on Form S-1, No. 333-1328
  
  ITEM 9.    UNDERTAKINGS.
  
             (a)        The undersigned Registrant hereby undertakes:
  
                        (1)        To file, during any period in which offers or
                                   sales are being made, a post-effective
                                   amendment to this Registration Statement:
  
                                   (i)        To include any prospectus required
                                              by Section 10(a)(3) of the
                                              Securities Act of 1933;
  
                                   (ii)       To reflect in the prospectus any
                                              facts or events arising after the
                                              effective date of the Registration
                                              Statement (or the most recent
                                              post-effective amendment thereof)
                                              which, individually or in the
                                              aggregate, represent a fundamental
                                              change in the information set forth
                                              in the Registration Statement; and
  6
                                        -6-
  
                                   (iii)      To include any material information
                                              with respect to the plan of
                                              distribution not previously
                                              disclosed in the Registration
                                              Statement or any material change to
                                              such information in the Registration
                                              Statement;
  
                                   provided, however, that paragraphs (a)(1)(i)
                                   and (a)(1)(ii) do not apply if the information
                                   required to be included in a post-effective
                                   amendment by those paragraphs is contained in
                                   periodic reports filed with or furnished to the
                                   Commission by the Registrant pursuant to
                                   Section 13 or Section 15(d) of the Securities
                                   Exchange Act of 1934 that are incorporated by
                                   reference in the Registration Statement.
  
                        (2)        That, for the purpose of determining any
                                   liability under the Securities Act of 1933,
                                   each such post-effective amendment shall be
                                   deemed to be a new registration statement
                                   relating to the securities offered therein, and
                                   the offering of such securities at that time
                                   shall be deemed to be the initial bona fide
                                   offering thereof.
  
                        (3)        To remove from registration by means of a
                                   post-effective amendment any of the securities
                                   being registered which remain unsold at the
                                   termination of the offering.
  
             (b)        The undersigned Registrant hereby undertakes that, for
                        purposes of determining any liability under the Securities
                        Act of 1933, each filing of the Registrant's annual report
                        pursuant to Section 13(a) or Section 15(d) of the
                        Securities Exchange Act of 1934 (and, where applicable,
                        each filing of any employee benefit plan's annual report
                        pursuant to Section 15(d) of the Securities Exchange Act
                        of 1934) that is incorporated by reference in the
                        Registration Statement shall be deemed to be a new
                        registration statement relating to the securities offered
                        therein, and the offering of such securities at that time
                        shall be deemed to be the initial bona fide offering
                        thereof.
  
             (c)        Insofar as indemnification for liabilities arising under
                        the Securities Act of 1933 may be permitted to directors,
                        officers and controlling persons of the Registrant
                        pursuant to the foregoing provisions, or otherwise, the
                        Registrant has been advised that in the opinion of the
                        Securities and Exchange Commission such indemnification is
                        against public policy as expressed in the Act and is,
                        therefore, unenforceable. In the event that a claim for
                        indemnification against such liabilities (other than the
                        payment by the Registrant of expenses incurred or paid by
                        a director, officer or controlling person of the
                        Registrant in the successful defense of any action, suit
                        or proceeding) is asserted by such director, officer or
                        controlling person in connection with the securities being
                        registered, the Registrant will, unless in the opinion of
                        its counsel the matter has been settled by controlling
                        precedent, submit to a court of appropriate jurisdiction
                        the question whether such indemnification by it is against
                        public policy as expressed in the Act and will be governed
                        by the final adjudication of such issue.
  7
                                        -7-
  
                                     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 Billerica, the Commonwealth of Massachusetts, on this
  24th day of May, 2001.
  
                                        SIPEX CORPORATION
  
                                        By:   /s/  James E. Donegan
                                             ------------------------------------
                                             James E. Donegan
                                             Chairman of the Board of Directors
                                             and Chief Executive Officer
  
                                  POWER OF ATTORNEY
  
             EACH SUCH PERSON WHOSE SIGNATURE appears below constitutes and
  appoints, jointly and severally, James E. Donegan and Frank R. DiPietro and each
  of them, with full power to act without the other, his true and lawful
  attorney-in-fact and agent, with the power of substitution and resubstitution,
  for him and in his name, place and stead, in any and all capacities, to sign any
  amendments to this Registration Statement on Form S-8 (including post-effective
  amendments) and to file the same, with all exhibits thereto, and other documents
  in connection therewith, with the Securities and Exchange Commission, hereby
  ratifying and confirming all that said attorney-in-fact, or his or her
  substitute or substitutes, 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 by the following persons in the
  capacities and on the date indicated.
  SIGNATURE                                        TITLE                                         DATE
  /s/  James E. Donegan                         Chairman of the Board of Directors, Chief                    May 24, 2001
    --------------------------------------        Executive Officer and Director
    James E. Donegan
  
    /s/  Frank R. DiPietro                        Executive Vice President, Finance, Chief                     May 24, 2001
    --------------------------------------        Financial Officer, Treasurer (principal
    Frank R. DiPietro                             financial officer and accounting officer)
                                                  and Clerk
  
    /s/  Manfred Loeb                             Director                                                     May 24, 2001
    --------------------------------------
    Manfred Loeb
  
    /s/  Lionel H. Olmer                          Director                                                     May 24, 2001
    --------------------------------------
    Lionel H. Olmer
  
    /s/  John L. Sprague                          Director                                                     May 24, 2001
    --------------------------------------
    John L. Sprague
  
    /s/  Doug McBunnie                            Director                                                     May 24, 2001
    --------------------------------------
    Doug McBurnie
  
    /s/  Willy Sansen                             Director                                                     May 24, 2001
    --------------------------------------
    Willy Sansen
  8
                                        -8-
  Exhibit                     Description of Exhibit
  4.1*      Restated Articles of Organization of the Registrant.
  
            4.2*      Restated By-Laws of the Registrant.
  
            4.3       SIPEX Corporation 2000 Non-Qualified Stock Option
                      Plan.
  
            4.4       Form of Non-Qualified Stock Option Agreement (Plan).
  
            4.5       Form of Non-Qualified Stock Option Agreement
                      (Non-Plan).
  
            4.6       Non-Qualified Stock Option Agreement dated January 16,
                      2001 by and between the Registrant and Bruce Diamond.
  
            5.1       Opinion of Testa, Hurwitz & Thibeault, LLP.
  
            23.1      Consent of Testa, Hurwitz & Thibeault, LLP (contained
                      in its opinion as Exhibit 5.1).
  
            23.2      Consent of  KPMG, LLP.
  
            23.3      Consent of Sallmann, Yang & Alameda.
  
            24.1      Power of Attorney (included as part of the signature
                      page of this Registration Statement).
  *Incorporated by reference to Exhibits to the Registrant's Registration
  Statement on Form S-1, No. 333-1328