content: <PAGE>   1
                As filed with the Securities and Exchange Commission
                                   on May 29, 2001
  
                                                        Registration No. 333-_____
  
  
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D. C. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                                    ALTAREX CORP.
               (Exact name of registrant as specified in its charter)
  
           PROVINCE OF ALBERTA, CANADA                         04-3416812
         (State or other jurisdiction of                    (I.R.S. Employer
          incorporation or organization)                 Identification Number)
    610 LINCOLN STREET, WALTHAM, MASSACHUSETTS                   02451
     (Address of Principal Executive Offices)                  (Zip Code)
  
                           ALTAREX CORP. STOCK OPTION PLAN
                              (Full title of the Plan)
  
                                  RICHARD E. BAGLEY
                               CHIEF EXECUTIVE OFFICER
                                    ALTAREX CORP.
                                 610 LINCOLN STREET
                            WALTHAM, MASSACHUSETTS 02451
  
                                   WITH A COPY TO:
  
                               Stuart M. Falber, Esq.
                                  Hale and Dorr LLP
                                   60 State Street
                             Boston, Massachusetts 02109
                                   (617) 526-6000
  
              (Name, address, including zip code, and telephone number,
                     including area code, of agents for service)
  
                           CALCULATION OF REGISTRATION FEE
  
  <TABLE>
  <CAPTION>
  ------------------------------------------------------------------------------------------------
  Title of                                 Proposed Maximum     Proposed Maximum      Amount of
  Securities           Amount to be        Offering Price       Aggregate             Registration
  to be Registered     Registered          Per Share            Offering Price        Fee
  ------------------------------------------------------------------------------------------------
  <S>                  <C>                 <C>                  <C>                   <C>
  Common Shares,
  no par value         5,455,312 shares       $2.0305 (1)       $11,077,011.02 (1)      $2,769.25
  ------------------------------------------------------------------------------------------------
  </TABLE>
  
  (1)  Estimated solely for the purpose of calculating the registration fee, based
       upon the average of the high and low prices of the Common Shares on the
       Toronto Stock Exchange on May 22, 2001 and the noon rate of exchange, as
       reported by the Federal Reserve Bank of New York, for the conversion of
       Canadian dollars into United States dollars on May 22, 2001, in accordance
       with Rules 457(c) and 457(h) of the Securities Act of 1933.
  <PAGE>   2
                                  EXPLANATORY NOTE
  
  This Registration Statement on Form S-8 is being filed to register the Common
  Shares of AltaRex Corp. (the "Company" or "Registrant") issuable pursuant to the
  AltaRex Corp. Stock Option Plan (the "Plan").
  
  
  
  
  
                                        -2-
  <PAGE>   3
  PART I.       INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
                The information required by Part I is included in documents sent
  or given to participants in the Plan pursuant to Rule 428(b)(1) of the
  Securities Act of 1933, as amended (the "Securities Act").
  
  PART II.      INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
  
           Item 3.   Incorporation of Certain Documents by Reference
  
                The following documents, which are filed with the Securities and
  Exchange Commission (the "Commission"), are incorporated in this Registration
  Statement by reference:
  
                (1) The Registrant's latest annual report filed pursuant to
           Sections 13(a) or 15(d) of the Securities Exchange Act of 1934, as
           amended (the "Exchange Act").
  
                (2) All other reports filed pursuant to Sections 13(a) or 15(d) of
           the Exchange Act since the end of the fiscal year covered by the annual
           report referred to in (1) above.
  
                (3) The Registrant's Registration Statement on Form 20-F, as
           amended, filed with the Commission pursuant to Section 12(g) of the
           Exchange Act.
  
                All documents subsequently filed 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 Common Shares offered hereby
  have been sold or which deregisters all Common Shares then remaining unsold,
  shall be deemed to be incorporated by reference herein and to be part hereof
  from the date of the filing of such documents. Any statement contained in a
  document incorporated or deemed to be incorporated by reference herein shall be
  deemed to be modified or superseded for purposes of this Registration Statement
  to the extent that a statement contained herein or in any other subsequently
  filed document which also is or is deemed to be incorporated by reference herein
  modifies or supersedes such statement. Any statement so modified or superseded
  shall be deemed, except as so modified or superseded, to constitute a part of
  this Registration Statement.
  
           Item 4.   Description of Securities
  
                Not applicable.
  
           Item 5.   Interests of Named Experts and Counsel
  
                Not Applicable.
  
           Item 6.   Indemnification of Directors and Officers
  
  
                                        -3-
  <PAGE>   4
                Section Seven of the Company's Bylaws provides that directors and
  officers of the Company are not liable for (a) the acts, receipts, neglects or
  defaults of any other director or officer or employee, (b) joining in any
  receipt or other act for conformity, or for any loss, damage or expense
  happening to the Company through the insufficiency or deficiency of title to any
  property acquired for or on behalf of the Company, (c) the insufficiency or
  deficiency of any security in or upon which any of the moneys of the Company
  shall be invested, (d) any loss or damage arising from the bankruptcy,
  insolvency or tortious acts of any person with whom any of the moneys,
  securities or effects of the Company shall be deposited, (e) any loss occasioned
  by any error of judgment or oversight on the part of the director or officer, or
  (f) any other loss, damage or misfortune whatsoever which shall happen in the
  execution of the duties of the director or officer's office or in relation
  thereto, unless occasioned by the director or officer's own willful neglect or
  default. This limitation on liability is subject to the director or officer
  acting honestly and in good faith, with a view to the best interests of the
  Company, and in the case of a criminal or administrative action or proceeding
  that is enforced by a monetary penalty, subject to the director or officer
  having reasonable grounds for believing that his conduct was lawful.
  
                Section Seven of the Company's Bylaws further provides that,
  subject to the approval of the Court of Queen's Bench of Alberta, the Company
  shall indemnify directors and officers against all costs, charges and expenses,
  including an amount paid to settle an action or satisfy a judgment, reasonably
  incurred by the director or officer in respect of any civil, criminal or
  administrative action or proceeding to which the director or officer is made a
  party by reason of being or having been a director or officer. The Company's
  indemnification obligation is limited to situations in which (a) the director or
  officer acted honestly and in good faith with a view to the best interests of
  the Company; and (b) in the case of a criminal or administrative action or
  proceeding that is enforced by a monetary penalty, the director or officer had
  reasonable grounds for believing that his or her conduct was lawful.
  
                Notwithstanding the Company's Bylaws, a director or officer or
  former director or officer or a person who acts or acted at the Company's
  request as a director or officer of a body corporate of which the Company is or
  was a shareholder or creditor is entitled to indemnity from the Company in
  respect of all costs, charges and expenses reasonably incurred by him in
  connection with the defense of any civil, criminal or administrative action or
  proceeding to which he is made a party by reason of being or having been a
  director or officer of the Company or body corporate, provided such individual
  was substantially successful on the merits in his defense of such action or
  proceeding, he fulfills the conditions set forth in the paragraph above and is
  fairly and reasonably entitled to indemnity.
  
                Section Seven of the Company's Bylaws further provides that the
  Company may purchase and maintain insurance for the benefit of its directors and
  officers against any liability incurred by the director or officer by virtue of
  his or her office except when the liability relates to the director or officer's
  failure to act honestly and in good faith with a view to the best interests of
  the Company.
  
                The limitations on liability and the indemnification provisions
  contained in Section Seven of the Registrant's Bylaws are subject to the
  limitations set forth in the Business Corporation Act, as amended, of Alberta
  Canada.
  
           Item 7.   Exemption from Registration Claimed
  
  
                                        -4-
  <PAGE>   5
                Not applicable.
  
           Item 8.   Exhibits
  
  <TABLE>
  <CAPTION>
           Exhibit
           Number         Description
  <S>                     <C>
  
           4.1 (1)        Articles of Incorporation of the Registrant, as amended
           4.2 (1)        Articles of Amalgamation of the Registrant, as amended
           4.3 (1)        By-Laws of the Registrant
           4.4            Specimen certificate for shares of Common Stock
           4.5 (2)        AltaRex Corp. Stock Option Plan, as amended
           5.1            Opinion of McCarthy Tetrault
           23.1           Consent of McCarthy Tetrault (included in Exhibit 5.1)
           23.2           Consent of Arthur Andersen LLP
           23.3           Consent of Ernst & Young LLP
           24             Power of Attorney (included on signature page to this Registration Statement)
  </TABLE>
  
  ---------
  (1)      Incorporated herein by reference from the Registrant's Registration
           Statement on Form 20-F, as amended.
  (2)      Incorporated herein by reference from the Registrant's Amended Annual
           Report on Form 20-F/A filed with the Commission on September 21, 2000.
  
           Item 9.   Undertakings
  
           1.       The Registrant hereby undertakes:
  
                    (a)   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.
                          Notwithstanding the foregoing, any increase or
                          decrease in volume of securities offered (if the
                          total dollar value of securities offered would not
                          exceed that which was registered) and any deviation
                          from the low or high end of the estimated maximum
                          offering range may be reflected in the form of
                          prospectus filed with the Commission pursuant to Rule
                          424(b) if, in the aggregate, the changes in volume
                          and price represent no more than 20 percent change in
                          the maximum aggregate offering
  
  
                                        -5-
  <PAGE>   6
                          price set forth in the "Calculation of Registration
                          Fee" table in the effective Registration Statement.
  
                          (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 1(a)(i) and 1(a)(ii) do not
                apply if the Registration Statement is on Form S-3, Form S-8 or
                Form F-3, and 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 15(d) of the Securities
                Exchange Act of 1934 that are incorporated by reference in the
                Registration Statement.
  
                    (b) That, for the purpose of determining any liability under
                the Securities Act, 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.
  
                    (c) 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.
  
           2.   The Registrant hereby undertakes that, for purposes of determining
  any liability under the Securities Act, each filing of the Registrant's annual
  report pursuant to Section 13(a) or Section 15(d) of the Exchange Act 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.
  
           3.   Insofar as indemnification for liabilities arising under the
  Securities Act 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 Commission such
  indemnification is against public policy as expressed in the Securities 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 Securities Act and will be governed by the final
  adjudication of such issue.
  
  
                                        -6-
  <PAGE>   7
                                     SIGNATURES
  
           Pursuant to the requirements of the Securities Act, 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 Waltham, Commonwealth of Massachusetts, on this 25th
  day of May, 2001.
  
                                         ALTAREX CORP.
  
  
  
                                         By:  /s/ Edward M. Fitzgerald
                                             -------------------------------------
                                         Name:  Edward M. Fitzgerald
                                         Title: Senior Vice President &
                                                Chief Financial Officer
  
  
  
                                        -7-
  <PAGE>   8
                          SIGNATURES AND POWER OF ATTORNEY
  
           We, the undersigned officers and directors of AltaRex Corp., hereby
  severally constitute and appoint Richard E. Bagley and Edward M. Fitzgerald, and
  each of them singly, our true and lawful attorneys with full power to any of
  them, and to each of them singly, to sign for us and in our names in the
  capacities indicated below the Registration Statement on Form S-8 filed herewith
  and any and all pre-effective and post-effective amendments to said Registration
  Statement and generally to do all such things in our name and behalf in our
  capacities as officers and directors to enable AltaRex Corp. to comply with the
  provisions of the Securities Act of 1933 and all requirements of the Securities
  and Exchange Commission, hereby ratifying and confirming our signatures as they
  may be signed by our said attorneys, or any of them, to said Registration
  Statement and any and all amendments thereto.
  
           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/ Richard E. Bagley              President, Chief Executive Officer and           May 25, 2001
  -----------------------------        Director (Principal Executive Officer)
     Richard E. Bagley
  
  
    /s/ Edward M. Fitzgerald           Senior Vice President and Chief Financial        May 25, 2001
  -----------------------------        Officer (Principal Financial
     Edward M. Fitzgerald              and Accounting Officer)
  
  
    /s/ Antoine A. Noujaim             Director and Chairman of the Board               May 25, 2001
  -----------------------------
     Antoine A. Noujaim
  
  
    /s/ William R. McMahan             Director                                         May 25, 2001
  -----------------------------
     William R. McMahan
  
  
    /s/ Monique Begin                  Director                                         May 25, 2001
  -----------------------------
      Monique Begin
  
  
    /s/ Jim A. Wright                  Director                                         May 25, 2001
  -----------------------------
     Jim A. Wright
  
  
    /s/ Normand Balthazard             Director                                         May 25, 2001
  -----------------------------
   Normand Balthazard
  
  
    /s/ William R. Darrow              Director                                         May 25, 2001
  -----------------------------
     William R. Darrow
  
  
    /s/ Robert H. Uhl                  Director                                         May 25, 2001
  -----------------------------
      Robert H. Uhl
  
  
    /s/ Bruce D. Brydon                Director                                         May 25, 2001
  -----------------------------
     Bruce D. Brydon
  </TABLE>
  
  
                                        -8-
  <PAGE>   9
                                    EXHIBIT INDEX
  
  
  <TABLE>
  <CAPTION>
           Exhibit
           Number          Description
  <S>                      <C>
  
           4.1 (1)         Articles of Incorporation of the Registrant, as amended
           4.2 (1)         Articles of Amalgamation of the Registrant, as amended
           4.3 (1)         By-Laws of the Registrant
           4.4             Specimen certificate for shares of Common Stock
           4.5 (2)         AltaRex Corp. Stock Option Plan, as amended
           5.1             Opinion of McCarthy Tetrault
           23.1            Consent of McCarthy Tetrault (included in Exhibit 5.1)
           23.2            Consent of Arthur Andersen LLP
           23.3            Consent of Ernst & Young LLP
           24              Power of Attorney (included on signature page to this Registration Statement)
  </TABLE>
  
  
  ---------
  (1)      Incorporated herein by reference from the Registrant's Registration
           Statement on Form 20-F, as amended.
  (2)      Incorporated herein by reference from the Registrant's Amended Annual
           Report on Form 20-F/A filed with the Commission on September 21, 2000.
  
  
                                        -9-
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text: 1
                As filed with the Securities and Exchange Commission
                                   on May 29, 2001
  
                                                        Registration No. 333-_____
  
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D. C. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                                    ALTAREX CORP.
               (Exact name of registrant as specified in its charter)
  
           PROVINCE OF ALBERTA, CANADA                         04-3416812
         (State or other jurisdiction of                    (I.R.S. Employer
          incorporation or organization)                 Identification Number)
    610 LINCOLN STREET, WALTHAM, MASSACHUSETTS                   02451
     (Address of Principal Executive Offices)                  (Zip Code)
  
                           ALTAREX CORP. STOCK OPTION PLAN
                              (Full title of the Plan)
  
                                  RICHARD E. BAGLEY
                               CHIEF EXECUTIVE OFFICER
                                    ALTAREX CORP.
                                 610 LINCOLN STREET
                            WALTHAM, MASSACHUSETTS 02451
  
                                   WITH A COPY TO:
  
                               Stuart M. Falber, Esq.
                                  Hale and Dorr LLP
                                   60 State Street
                             Boston, Massachusetts 02109
                                   (617) 526-6000
  
              (Name, address, including zip code, and telephone number,
                     including area code, of agents for service)
  
                           CALCULATION OF REGISTRATION FEE
  ------------------------------------------------------------------------------------------------
  Title of                                 Proposed Maximum     Proposed Maximum      Amount of
  Securities           Amount to be        Offering Price       Aggregate             Registration
  to be Registered     Registered          Per Share            Offering Price        Fee
  ------------------------------------------------------------------------------------------------
  Common Shares,
  no par value         5,455,312 shares       $2.0305 (1)       $11,077,011.02 (1)      $2,769.25
  ------------------------------------------------------------------------------------------------
  (1)  Estimated solely for the purpose of calculating the registration fee, based
       upon the average of the high and low prices of the Common Shares on the
       Toronto Stock Exchange on May 22, 2001 and the noon rate of exchange, as
       reported by the Federal Reserve Bank of New York, for the conversion of
       Canadian dollars into United States dollars on May 22, 2001, in accordance
       with Rules 457(c) and 457(h) of the Securities Act of 1933.
  2
                                  EXPLANATORY NOTE
  
  This Registration Statement on Form S-8 is being filed to register the Common
  Shares of AltaRex Corp. (the "Company" or "Registrant") issuable pursuant to the
  AltaRex Corp. Stock Option Plan (the "Plan").
  
                                        -2-
  3
  PART I.       INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
                The information required by Part I is included in documents sent
  or given to participants in the Plan pursuant to Rule 428(b)(1) of the
  Securities Act of 1933, as amended (the "Securities Act").
  
  PART II.      INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
  
           Item 3.   Incorporation of Certain Documents by Reference
  
                The following documents, which are filed with the Securities and
  Exchange Commission (the "Commission"), are incorporated in this Registration
  Statement by reference:
  
                (1) The Registrant's latest annual report filed pursuant to
           Sections 13(a) or 15(d) of the Securities Exchange Act of 1934, as
           amended (the "Exchange Act").
  
                (2) All other reports filed pursuant to Sections 13(a) or 15(d) of
           the Exchange Act since the end of the fiscal year covered by the annual
           report referred to in (1) above.
  
                (3) The Registrant's Registration Statement on Form 20-F, as
           amended, filed with the Commission pursuant to Section 12(g) of the
           Exchange Act.
  
                All documents subsequently filed 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 Common Shares offered hereby
  have been sold or which deregisters all Common Shares then remaining unsold,
  shall be deemed to be incorporated by reference herein and to be part hereof
  from the date of the filing of such documents. Any statement contained in a
  document incorporated or deemed to be incorporated by reference herein shall be
  deemed to be modified or superseded for purposes of this Registration Statement
  to the extent that a statement contained herein or in any other subsequently
  filed document which also is or is deemed to be incorporated by reference herein
  modifies or supersedes such statement. Any statement so modified or superseded
  shall be deemed, except as so modified or superseded, to constitute a part of
  this Registration Statement.
  
           Item 4.   Description of Securities
  
                Not applicable.
  
           Item 5.   Interests of Named Experts and Counsel
  
                Not Applicable.
  
           Item 6.   Indemnification of Directors and Officers
  
                                        -3-
  4
                Section Seven of the Company's Bylaws provides that directors and
  officers of the Company are not liable for (a) the acts, receipts, neglects or
  defaults of any other director or officer or employee, (b) joining in any
  receipt or other act for conformity, or for any loss, damage or expense
  happening to the Company through the insufficiency or deficiency of title to any
  property acquired for or on behalf of the Company, (c) the insufficiency or
  deficiency of any security in or upon which any of the moneys of the Company
  shall be invested, (d) any loss or damage arising from the bankruptcy,
  insolvency or tortious acts of any person with whom any of the moneys,
  securities or effects of the Company shall be deposited, (e) any loss occasioned
  by any error of judgment or oversight on the part of the director or officer, or
  (f) any other loss, damage or misfortune whatsoever which shall happen in the
  execution of the duties of the director or officer's office or in relation
  thereto, unless occasioned by the director or officer's own willful neglect or
  default. This limitation on liability is subject to the director or officer
  acting honestly and in good faith, with a view to the best interests of the
  Company, and in the case of a criminal or administrative action or proceeding
  that is enforced by a monetary penalty, subject to the director or officer
  having reasonable grounds for believing that his conduct was lawful.
  
                Section Seven of the Company's Bylaws further provides that,
  subject to the approval of the Court of Queen's Bench of Alberta, the Company
  shall indemnify directors and officers against all costs, charges and expenses,
  including an amount paid to settle an action or satisfy a judgment, reasonably
  incurred by the director or officer in respect of any civil, criminal or
  administrative action or proceeding to which the director or officer is made a
  party by reason of being or having been a director or officer. The Company's
  indemnification obligation is limited to situations in which (a) the director or
  officer acted honestly and in good faith with a view to the best interests of
  the Company; and (b) in the case of a criminal or administrative action or
  proceeding that is enforced by a monetary penalty, the director or officer had
  reasonable grounds for believing that his or her conduct was lawful.
  
                Notwithstanding the Company's Bylaws, a director or officer or
  former director or officer or a person who acts or acted at the Company's
  request as a director or officer of a body corporate of which the Company is or
  was a shareholder or creditor is entitled to indemnity from the Company in
  respect of all costs, charges and expenses reasonably incurred by him in
  connection with the defense of any civil, criminal or administrative action or
  proceeding to which he is made a party by reason of being or having been a
  director or officer of the Company or body corporate, provided such individual
  was substantially successful on the merits in his defense of such action or
  proceeding, he fulfills the conditions set forth in the paragraph above and is
  fairly and reasonably entitled to indemnity.
  
                Section Seven of the Company's Bylaws further provides that the
  Company may purchase and maintain insurance for the benefit of its directors and
  officers against any liability incurred by the director or officer by virtue of
  his or her office except when the liability relates to the director or officer's
  failure to act honestly and in good faith with a view to the best interests of
  the Company.
  
                The limitations on liability and the indemnification provisions
  contained in Section Seven of the Registrant's Bylaws are subject to the
  limitations set forth in the Business Corporation Act, as amended, of Alberta
  Canada.
  
           Item 7.   Exemption from Registration Claimed
  
                                        -4-
  5
                Not applicable.
  
           Item 8.   Exhibits
  Exhibit
           Number         Description
  4.1 (1)        Articles of Incorporation of the Registrant, as amended
           4.2 (1)        Articles of Amalgamation of the Registrant, as amended
           4.3 (1)        By-Laws of the Registrant
           4.4            Specimen certificate for shares of Common Stock
           4.5 (2)        AltaRex Corp. Stock Option Plan, as amended
           5.1            Opinion of McCarthy Tetrault
           23.1           Consent of McCarthy Tetrault (included in Exhibit 5.1)
           23.2           Consent of Arthur Andersen LLP
           23.3           Consent of Ernst & Young LLP
           24             Power of Attorney (included on signature page to this Registration Statement)
  ---------
  (1)      Incorporated herein by reference from the Registrant's Registration
           Statement on Form 20-F, as amended.
  (2)      Incorporated herein by reference from the Registrant's Amended Annual
           Report on Form 20-F/A filed with the Commission on September 21, 2000.
  
           Item 9.   Undertakings
  
           1.       The Registrant hereby undertakes:
  
                    (a)   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.
                          Notwithstanding the foregoing, any increase or
                          decrease in volume of securities offered (if the
                          total dollar value of securities offered would not
                          exceed that which was registered) and any deviation
                          from the low or high end of the estimated maximum
                          offering range may be reflected in the form of
                          prospectus filed with the Commission pursuant to Rule
                          424(b) if, in the aggregate, the changes in volume
                          and price represent no more than 20 percent change in
                          the maximum aggregate offering
  
                                        -5-
  6
                          price set forth in the "Calculation of Registration
                          Fee" table in the effective Registration Statement.
  
                          (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 1(a)(i) and 1(a)(ii) do not
                apply if the Registration Statement is on Form S-3, Form S-8 or
                Form F-3, and 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 15(d) of the Securities
                Exchange Act of 1934 that are incorporated by reference in the
                Registration Statement.
  
                    (b) That, for the purpose of determining any liability under
                the Securities Act, 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.
  
                    (c) 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.
  
           2.   The Registrant hereby undertakes that, for purposes of determining
  any liability under the Securities Act, each filing of the Registrant's annual
  report pursuant to Section 13(a) or Section 15(d) of the Exchange Act 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.
  
           3.   Insofar as indemnification for liabilities arising under the
  Securities Act 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 Commission such
  indemnification is against public policy as expressed in the Securities 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 Securities Act and will be governed by the final
  adjudication of such issue.
  
                                        -6-
  7
                                     SIGNATURES
  
           Pursuant to the requirements of the Securities Act, 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 Waltham, Commonwealth of Massachusetts, on this 25th
  day of May, 2001.
  
                                         ALTAREX CORP.
  
                                         By:  /s/ Edward M. Fitzgerald
                                             -------------------------------------
                                         Name:  Edward M. Fitzgerald
                                         Title: Senior Vice President &
                                                Chief Financial Officer
  
                                        -7-
  8
                          SIGNATURES AND POWER OF ATTORNEY
  
           We, the undersigned officers and directors of AltaRex Corp., hereby
  severally constitute and appoint Richard E. Bagley and Edward M. Fitzgerald, and
  each of them singly, our true and lawful attorneys with full power to any of
  them, and to each of them singly, to sign for us and in our names in the
  capacities indicated below the Registration Statement on Form S-8 filed herewith
  and any and all pre-effective and post-effective amendments to said Registration
  Statement and generally to do all such things in our name and behalf in our
  capacities as officers and directors to enable AltaRex Corp. to comply with the
  provisions of the Securities Act of 1933 and all requirements of the Securities
  and Exchange Commission, hereby ratifying and confirming our signatures as they
  may be signed by our said attorneys, or any of them, to said Registration
  Statement and any and all amendments thereto.
  
           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/ Richard E. Bagley              President, Chief Executive Officer and           May 25, 2001
  -----------------------------        Director (Principal Executive Officer)
     Richard E. Bagley
  
    /s/ Edward M. Fitzgerald           Senior Vice President and Chief Financial        May 25, 2001
  -----------------------------        Officer (Principal Financial
     Edward M. Fitzgerald              and Accounting Officer)
  
    /s/ Antoine A. Noujaim             Director and Chairman of the Board               May 25, 2001
  -----------------------------
     Antoine A. Noujaim
  
    /s/ William R. McMahan             Director                                         May 25, 2001
  -----------------------------
     William R. McMahan
  
    /s/ Monique Begin                  Director                                         May 25, 2001
  -----------------------------
      Monique Begin
  
    /s/ Jim A. Wright                  Director                                         May 25, 2001
  -----------------------------
     Jim A. Wright
  
    /s/ Normand Balthazard             Director                                         May 25, 2001
  -----------------------------
   Normand Balthazard
  
    /s/ William R. Darrow              Director                                         May 25, 2001
  -----------------------------
     William R. Darrow
  
    /s/ Robert H. Uhl                  Director                                         May 25, 2001
  -----------------------------
      Robert H. Uhl
  
    /s/ Bruce D. Brydon                Director                                         May 25, 2001
  -----------------------------
     Bruce D. Brydon
  -8-
  9
                                    EXHIBIT INDEX
  Exhibit
           Number          Description
  4.1 (1)         Articles of Incorporation of the Registrant, as amended
           4.2 (1)         Articles of Amalgamation of the Registrant, as amended
           4.3 (1)         By-Laws of the Registrant
           4.4             Specimen certificate for shares of Common Stock
           4.5 (2)         AltaRex Corp. Stock Option Plan, as amended
           5.1             Opinion of McCarthy Tetrault
           23.1            Consent of McCarthy Tetrault (included in Exhibit 5.1)
           23.2            Consent of Arthur Andersen LLP
           23.3            Consent of Ernst & Young LLP
           24              Power of Attorney (included on signature page to this Registration Statement)
  ---------
  (1)      Incorporated herein by reference from the Registrant's Registration
           Statement on Form 20-F, as amended.
  (2)      Incorporated herein by reference from the Registrant's Amended Annual
           Report on Form 20-F/A filed with the Commission on September 21, 2000.
  
                                        -9-