<PAGE>   1

   As filed with the Securities and Exchange Commission on September 1, 2000
                                                     Registration No. 333-______

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   ----------

                                    FORM S-8
             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                              Hycor Biomedical Inc.

             (Exact Name of Registrant as Specified in Its Charter)

                DELAWARE                                 58-1437178
     (State or Other Jurisdiction of        (I.R.S. Employer Identification No.)
     Incorporation or Organization)

           7272 CHAPMAN AVENUE                             92841
        GARDEN GROVE, CALIFORNIA                         (Zip Code)
(Address of Principal Executive Offices)


                              HYCOR BIOMEDICAL INC.
                       NONQUALIFIED STOCK OPTION PLAN FOR
                       NON-EMPLOYEE DIRECTORS, AS AMENDED
                            (Full Title of the Plan)

                                Reginald P. Jones
                Senior Vice President and Chief Financial Officer
                              Hycor Biomedical Inc.
                               7272 Chapman Avenue
                         Garden Grove, California 92841
                     (Name and Address of Agent For Service)

                                 (714) 933-3000
          (Telephone Number, Including Area Code, of Agent for Service)

                Please address a copy of all communications to:
                             Stephen D. Cooke, Esq.
                      Paul, Hastings, Janofsky & Walker LLP
                        695 Town Center Drive, 17th Floor
                        Costa Mesa, California 92626-1924
                            Telephone: (714) 668-6200

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
==============================================================================================================
                                                        Proposed              Proposed
 Title of                                               Maximum               Maximum
Securities                        Amount                Offering              Aggregate              Amount of
  to be                           to be                  Price                Offering             Registration
Registered                      Registered            Per Share(1)             Price                    Fee
--------------------------------------------------------------------------------------------------------------
<S>                             <C>                      <C>                 <C>                       <C>

Common Stock,
Par Value $0.01
Per Share                       175,000(2)               $7.00               $1,225,000                $324

==============================================================================================================
</TABLE>

(1)       Calculated pursuant to Rules 457(c) and 457(h)(1), based on the
          average of the high and low sale prices ($7.00 per share) of the
          Common Stock of the Registrant on the Nasdaq Stock Market on August
          29, 2000.

(2)       As presently constituted, plus such indeterminate number of shares as
          may be subject to Hycor Biomedical Inc.'s Non Qualified Stock Option
          Plan for Non-Employee Directors as a result of adjustment provisions
          set forth in such Plan and agreements entered into pursuant thereto.


<PAGE>   2

                     STATEMENT UNDER GENERAL INSTRUCTION E.
                      REGISTRATION OF ADDITIONAL SECURITIES

      The shares covered by this Registration Statement represent additional
shares of the Registrant's Common Stock that have become available for issuance
under the Hycor Biomedical Inc. Nonqualified Stock Option Plan for Non-Employee
Directors (the "Plan") as a result of an amendment increasing the number of
shares authorized for issuance thereunder from 150,000 to 325,000, which
amendment is reflected in the Amendment to Hycor Biomedical Inc. Nonqualified
Stock Option Plan for Non-Employee Directors (the "Amendment"), which is
included as Exhibit 4.2 hereto. The Amendment amends the Plan. Unless otherwise
noted herein, the contents of the Registrant's Form S-8 Registration Statement
(File No. 33-63798) relating to the Plan are incorporated by reference into this
Registration Statement.


                                     PART II


ITEM 8.        EXHIBITS


      Exhibit
      Number                                Description
      -------                               -----------

        4.1          Hycor Biomedical Inc. Nonqualified Stock Option Plan for
                     Non-Employee Directors (previously filed as Exhibit 10(17)
                     to the 10-Q Quarterly Report for Hycor Biomedical Inc. for
                     the period ended June 30, 1992, and which is incorporated
                     herein by reference)

        4.2          Amendment to Hycor Biomedical Inc. Nonqualified Stock
                     Option Plan for Non-Employee Directors

        5            Opinion of Paul, Hastings, Janofsky & Walker LLP as to the
                     legality of the securities being registered

       23.1          Consent of Deloitte & Touche LLP

       23.2          Consent of Paul, Hastings, Janofsky & Walker LLP (included
                     in the opinion filed as Exhibit 5)

       24            Power of Attorney authorizing J. David Tholen and Reginald
                     P. Jones to sign amendments to this Registration Statement
                     on behalf of officers and directors of the Registrant
                     (contained on Signature Page of Registration Statement)


                                       -2-

<PAGE>   3

                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Garden Grove, State of California, on this 29th day
of August, 2000


                                        HYCOR BIOMEDICAL INC.

                                        By: /s/ J. David Tholen
                                            ------------------------------------
                                            J. DAVID THOLEN, PRESIDENT AND
                                            CHIEF EXECUTIVE OFFICER


                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints J. David Tholen and Reginald P. Jones,
jointly and severally, his or her attorneys-in-fact, each with power of
substitution for him or her in any and all capacities, to sign any amendments to
this Registration Statement, and to file the same, with the exhibits thereto,
and other documents in connection therewith, with the Securities and Exchange
Commission hereby ratifying and confirming all that each of said
attorneys-in-fact, or his 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 below by the following persons in the
capacities and on the date indicated.



/s/ J. David Tholen                                      August 29, 2000
-----------------------------------------                ---------------
J. DAVID THOLEN, PRESIDENT, CHIEF                        Date
EXECUTIVE OFFICER AND DIRECTOR
(PRINCIPAL EXECUTIVE OFFICER)



/s/ Reginald P. Jones                                    August 29, 2000
-----------------------------------------                ---------------
REGINALD P. JONES, SENIOR VICE PRESIDENT,                Date
CHIEF FINANCIAL OFFICER AND DIRECTOR
(PRINCIPAL FINANCIAL OFFICER)



/s/ Armando Correa                                       August 29, 2000
-----------------------------------------                ---------------
ARMANDO CORREA,                                          Date
DIRECTOR, FINANCE
(PRINCIPAL ACCOUNTING OFFICER)



/s/ Samuel D. Anderson                                   August 29, 2000
-----------------------------------------                ---------------
SAMUEL D. ANDERSON, CHAIRMAN                             Date



/s/ David S. Gordon                                      August 29, 2000
-----------------------------------------                ---------------
DAVID S. GORDON, DIRECTOR                                Date


                                       -3-

<PAGE>   4

                                  EXHIBIT INDEX


      Exhibit
      Number                             Description
      -------                            -----------

        4.1          Hycor Biomedical Inc. Nonqualified Stock Option Plan for
                     Non-Employee Directors (previously filed as Exhibit 10(17)
                     to the 10-Q Quarterly Report for Hycor Biomedical Inc. for
                     the period ended June 30, 1992, and which is incorporated
                     herein by reference)

        4.2          Amendment to Hycor Biomedical Inc. Nonqualified Stock
                     Option Plan for Non-Employee Directors

        5            Opinion of Paul, Hastings, Janofsky & Walker LLP as to the
                     legality of the securities being registered

       23.1          Consent of Deloitte & Touche LLP

       23.2          Consent of Paul, Hastings, Janofsky & Walker LLP (included
                     in the opinion filed as Exhibit 5)

       24            Power of Attorney authorizing J. David Tholen and Reginald
                     P. Jones to sign amendments to this Registration Statement
                     on behalf of officers and directors of the Registrant
                     (contained on Signature Page of Registration Statement)


                                       -4-
[{"type": "S-8", "sequence": "1", "filename": "a65389s-8.txt", "description": "FORM S-8", "secsgml_size_bytes": 10434}]
{"company-data": {"conformed-name": "HYCOR BIOMEDICAL INC /DE/", "cik": "0000719447", "assigned-sic": "2835", "irs-number": "581437178", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-45102", "film-number": "715931"}, "business-address": {"street1": "7272 CHAPMAN AVE", "city": "GARDEN GROVE", "state": "CA", "zip": "92641", "phone": "7148959558"}, "mail-address": {"street2": "18800 VON KARMAN AVE", "city": "IRVINE", "state": "CA", "zip": "92715-1517"}, "former-company": {"former-conformed-name": "HYBRIDOMA SCIENCES INC", "date-changed": "19860813"}}
1

   As filed with the Securities and Exchange Commission on September 1, 2000
                                                     Registration No. 333-______

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   ----------

                                    FORM S-8
             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                              Hycor Biomedical Inc.

             (Exact Name of Registrant as Specified in Its Charter)

                DELAWARE                                 58-1437178
     (State or Other Jurisdiction of        (I.R.S. Employer Identification No.)
     Incorporation or Organization)

           7272 CHAPMAN AVENUE                             92841
        GARDEN GROVE, CALIFORNIA                         (Zip Code)
(Address of Principal Executive Offices)

                              HYCOR BIOMEDICAL INC.
                       NONQUALIFIED STOCK OPTION PLAN FOR
                       NON-EMPLOYEE DIRECTORS, AS AMENDED
                            (Full Title of the Plan)

                                Reginald P. Jones
                Senior Vice President and Chief Financial Officer
                              Hycor Biomedical Inc.
                               7272 Chapman Avenue
                         Garden Grove, California 92841
                     (Name and Address of Agent For Service)

                                 (714) 933-3000
          (Telephone Number, Including Area Code, of Agent for Service)

                Please address a copy of all communications to:
                             Stephen D. Cooke, Esq.
                      Paul, Hastings, Janofsky & Walker LLP
                        695 Town Center Drive, 17th Floor
                        Costa Mesa, California 92626-1924
                            Telephone: (714) 668-6200

                         CALCULATION OF REGISTRATION FEE
==============================================================================================================
                                                        Proposed              Proposed
 Title of                                               Maximum               Maximum
Securities                        Amount                Offering              Aggregate              Amount of
  to be                           to be                  Price                Offering             Registration
Registered                      Registered            Per Share(1)             Price                    Fee
--------------------------------------------------------------------------------------------------------------
Common Stock,
Par Value $0.01
Per Share                       175,000(2)               $7.00               $1,225,000                $324

==============================================================================================================
(1)       Calculated pursuant to Rules 457(c) and 457(h)(1), based on the
          average of the high and low sale prices ($7.00 per share) of the
          Common Stock of the Registrant on the Nasdaq Stock Market on August
          29, 2000.

(2)       As presently constituted, plus such indeterminate number of shares as
          may be subject to Hycor Biomedical Inc.'s Non Qualified Stock Option
          Plan for Non-Employee Directors as a result of adjustment provisions
          set forth in such Plan and agreements entered into pursuant thereto.
2

                     STATEMENT UNDER GENERAL INSTRUCTION E.
                      REGISTRATION OF ADDITIONAL SECURITIES

      The shares covered by this Registration Statement represent additional
shares of the Registrant's Common Stock that have become available for issuance
under the Hycor Biomedical Inc. Nonqualified Stock Option Plan for Non-Employee
Directors (the "Plan") as a result of an amendment increasing the number of
shares authorized for issuance thereunder from 150,000 to 325,000, which
amendment is reflected in the Amendment to Hycor Biomedical Inc. Nonqualified
Stock Option Plan for Non-Employee Directors (the "Amendment"), which is
included as Exhibit 4.2 hereto. The Amendment amends the Plan. Unless otherwise
noted herein, the contents of the Registrant's Form S-8 Registration Statement
(File No. 33-63798) relating to the Plan are incorporated by reference into this
Registration Statement.

                                     PART II

ITEM 8.        EXHIBITS

      Exhibit
      Number                                Description
      -------                               -----------

        4.1          Hycor Biomedical Inc. Nonqualified Stock Option Plan for
                     Non-Employee Directors (previously filed as Exhibit 10(17)
                     to the 10-Q Quarterly Report for Hycor Biomedical Inc. for
                     the period ended June 30, 1992, and which is incorporated
                     herein by reference)

        4.2          Amendment to Hycor Biomedical Inc. Nonqualified Stock
                     Option Plan for Non-Employee Directors

        5            Opinion of Paul, Hastings, Janofsky & Walker LLP as to the
                     legality of the securities being registered

       23.1          Consent of Deloitte & Touche LLP

       23.2          Consent of Paul, Hastings, Janofsky & Walker LLP (included
                     in the opinion filed as Exhibit 5)

       24            Power of Attorney authorizing J. David Tholen and Reginald
                     P. Jones to sign amendments to this Registration Statement
                     on behalf of officers and directors of the Registrant
                     (contained on Signature Page of Registration Statement)

                                       -2-
3

                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Garden Grove, State of California, on this 29th day
of August, 2000

                                        HYCOR BIOMEDICAL INC.

                                        By: /s/ J. David Tholen
                                            ------------------------------------
                                            J. DAVID THOLEN, PRESIDENT AND
                                            CHIEF EXECUTIVE OFFICER

                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints J. David Tholen and Reginald P. Jones,
jointly and severally, his or her attorneys-in-fact, each with power of
substitution for him or her in any and all capacities, to sign any amendments to
this Registration Statement, and to file the same, with the exhibits thereto,
and other documents in connection therewith, with the Securities and Exchange
Commission hereby ratifying and confirming all that each of said
attorneys-in-fact, or his 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 below by the following persons in the
capacities and on the date indicated.

/s/ J. David Tholen                                      August 29, 2000
-----------------------------------------                ---------------
J. DAVID THOLEN, PRESIDENT, CHIEF                        Date
EXECUTIVE OFFICER AND DIRECTOR
(PRINCIPAL EXECUTIVE OFFICER)

/s/ Reginald P. Jones                                    August 29, 2000
-----------------------------------------                ---------------
REGINALD P. JONES, SENIOR VICE PRESIDENT,                Date
CHIEF FINANCIAL OFFICER AND DIRECTOR
(PRINCIPAL FINANCIAL OFFICER)

/s/ Armando Correa                                       August 29, 2000
-----------------------------------------                ---------------
ARMANDO CORREA,                                          Date
DIRECTOR, FINANCE
(PRINCIPAL ACCOUNTING OFFICER)

/s/ Samuel D. Anderson                                   August 29, 2000
-----------------------------------------                ---------------
SAMUEL D. ANDERSON, CHAIRMAN                             Date

/s/ David S. Gordon                                      August 29, 2000
-----------------------------------------                ---------------
DAVID S. GORDON, DIRECTOR                                Date

                                       -3-
4

                                  EXHIBIT INDEX

      Exhibit
      Number                             Description
      -------                            -----------

        4.1          Hycor Biomedical Inc. Nonqualified Stock Option Plan for
                     Non-Employee Directors (previously filed as Exhibit 10(17)
                     to the 10-Q Quarterly Report for Hycor Biomedical Inc. for
                     the period ended June 30, 1992, and which is incorporated
                     herein by reference)

        4.2          Amendment to Hycor Biomedical Inc. Nonqualified Stock
                     Option Plan for Non-Employee Directors

        5            Opinion of Paul, Hastings, Janofsky & Walker LLP as to the
                     legality of the securities being registered

       23.1          Consent of Deloitte & Touche LLP

       23.2          Consent of Paul, Hastings, Janofsky & Walker LLP (included
                     in the opinion filed as Exhibit 5)

       24            Power of Attorney authorizing J. David Tholen and Reginald
                     P. Jones to sign amendments to this Registration Statement
                     on behalf of officers and directors of the Registrant
                     (contained on Signature Page of Registration Statement)

                                       -4-