<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.
                        2000 EMPLOYEE STOCK PURCHASE PLAN
                            (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                     300,000 shares            $7.00                $2,100,000               $555

==============================================================================================================
</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.


<PAGE>   2

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

ITEM 1.  PLAN INFORMATION*

ITEM 2.  REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION*

         *Information required by Part I to be contained in the Section 10(a)
         prospectus is omitted from the Registration Statement in accordance
         with Rule 428(a)(1) under the Securities Act and the Note to Part I of
         Form S-8.


                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE

         The following documents are hereby incorporated into this Registration
Statement and made a part hereof by this reference:

         (a)      The Annual Report on Form 10-K of Hycor Biomedical Inc. (the
                  "Company") for the fiscal year ended December 31, 1999, filed
                  with the Securities and Exchange Commission ("Commission")
                  pursuant to the Securities Exchange Act of 1934, as amended
                  (the "Exchange Act");

         (b)      The Quarterly Report on Form 10-Q for the Company for the
                  quarter ended March 31, 2000, filed with the Commission
                  pursuant to the Exchange Act;

         (c)      The Quarterly Report on Form 10-Q for the Company for the
                  quarter ended June 30, 2000, filed with the Commission
                  pursuant to the Exchange Act;

         (d)      All other reports filed pursuant to Section 13(a) or 15(d) of
                  the Exchange Act since the end of the fiscal year covered by
                  the Registrant document referred to in (a) above; and

         (e)      The description of the common stock contained in the Company's
                  registration statement filed under Section 12 of the Exchange
                  Act, including any amendment or report filed for the purpose
                  of updating such description.

         In addition, all documents filed by the Company with the Commission
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 have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated by reference into this Registration
Statement and to be a part hereof from the date of filing of such documents with
the Commission.

ITEM 4.  DESCRIPTION OF SECURITIES

         Not applicable

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         Not applicable

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Section 145 of the Delaware General Corporation Law authorizes a court
to award, or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances against reasonable expenses incurred
in defending against a claim. Article Twelfth of the Company's Certificate of
Incorporation, as amended, provides for indemnification of its directors,
officers, employees and other agents to the maximum extent permitted by the
Delaware General Corporation law.


ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED


                                       -2-

<PAGE>   3

         Not applicable


ITEM 8.  EXHIBITS

         The exhibits filed as part of this Registration Statement are as
follows:

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

      4             Hycor Biomedical Inc. 2000 Employee Stock Purchase Plan

      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)

ITEM 9.     UNDERTAKINGS

(1)      The Company 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;

                  (ii)     To reflect in the prospectus any facts or events
                           arising after the effective date of this 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 this Registration Statement;

                  (iii)    To include any material information with respect to
                           the plan of distribution not previously disclosed in
                           this Registration Statement or any material change to
                           such information in this Registration Statement;

                  provided, however, that the undertakings set forth in
                  paragraphs (a)(i) and (a)(ii) above 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 Company
                  pursuant to Section 13 or Section 15(d) of the Exchange Act
                  that are incorporated by reference in this Registration
                  Statement.

         (b)      That, for the purpose of determining any liability under the
                  Securities Act, each post-effective amendment to this
                  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)      To remove from registration by means of a post-effective
                  amendment any of the securities being registered that remain
                  unsold at the termination of the offering.

(2)      The Company hereby undertakes that, for purposes of determining any
liability under the Securities Act, each filing of the Company's annual report
pursuant to Section 13(a) or Section 15(d) of the Exchange Act that is
incorporated by reference in this 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
Company pursuant to the foregoing provisions, or otherwise, the Company has been
advised


                                       -3-

<PAGE>   4

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 Company of expenses incurred or paid by a director, officer
or controlling person of the Company 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 Company 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.


                                       -4-

<PAGE>   5

                                   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.

<TABLE>
<S>                                                <C>

/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
</TABLE>


                                       -5-

<PAGE>   6

                                  EXHIBIT INDEX




  Exhibits
  --------

      4             Hycor Biomedical Inc. 2000 Employee Stock Purchase Plan

      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)


                                       -6-
[{"type": "S-8", "sequence": "1", "filename": "a65388s-8.txt", "description": "FORM S-8", "secsgml_size_bytes": 15602}]
{"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": "333-45110", "film-number": "715985"}, "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.
                        2000 EMPLOYEE STOCK PURCHASE PLAN
                            (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                     300,000 shares            $7.00                $2,100,000               $555

==============================================================================================================
(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

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

ITEM 1.  PLAN INFORMATION*

ITEM 2.  REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION*

         *Information required by Part I to be contained in the Section 10(a)
         prospectus is omitted from the Registration Statement in accordance
         with Rule 428(a)(1) under the Securities Act and the Note to Part I of
         Form S-8.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE

         The following documents are hereby incorporated into this Registration
Statement and made a part hereof by this reference:

         (a)      The Annual Report on Form 10-K of Hycor Biomedical Inc. (the
                  "Company") for the fiscal year ended December 31, 1999, filed
                  with the Securities and Exchange Commission ("Commission")
                  pursuant to the Securities Exchange Act of 1934, as amended
                  (the "Exchange Act");

         (b)      The Quarterly Report on Form 10-Q for the Company for the
                  quarter ended March 31, 2000, filed with the Commission
                  pursuant to the Exchange Act;

         (c)      The Quarterly Report on Form 10-Q for the Company for the
                  quarter ended June 30, 2000, filed with the Commission
                  pursuant to the Exchange Act;

         (d)      All other reports filed pursuant to Section 13(a) or 15(d) of
                  the Exchange Act since the end of the fiscal year covered by
                  the Registrant document referred to in (a) above; and

         (e)      The description of the common stock contained in the Company's
                  registration statement filed under Section 12 of the Exchange
                  Act, including any amendment or report filed for the purpose
                  of updating such description.

         In addition, all documents filed by the Company with the Commission
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 have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated by reference into this Registration
Statement and to be a part hereof from the date of filing of such documents with
the Commission.

ITEM 4.  DESCRIPTION OF SECURITIES

         Not applicable

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         Not applicable

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Section 145 of the Delaware General Corporation Law authorizes a court
to award, or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances against reasonable expenses incurred
in defending against a claim. Article Twelfth of the Company's Certificate of
Incorporation, as amended, provides for indemnification of its directors,
officers, employees and other agents to the maximum extent permitted by the
Delaware General Corporation law.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

                                       -2-
3

         Not applicable

ITEM 8.  EXHIBITS

         The exhibits filed as part of this Registration Statement are as
follows:

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

      4             Hycor Biomedical Inc. 2000 Employee Stock Purchase Plan

      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)

ITEM 9.     UNDERTAKINGS

(1)      The Company 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;

                  (ii)     To reflect in the prospectus any facts or events
                           arising after the effective date of this 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 this Registration Statement;

                  (iii)    To include any material information with respect to
                           the plan of distribution not previously disclosed in
                           this Registration Statement or any material change to
                           such information in this Registration Statement;

                  provided, however, that the undertakings set forth in
                  paragraphs (a)(i) and (a)(ii) above 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 Company
                  pursuant to Section 13 or Section 15(d) of the Exchange Act
                  that are incorporated by reference in this Registration
                  Statement.

         (b)      That, for the purpose of determining any liability under the
                  Securities Act, each post-effective amendment to this
                  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)      To remove from registration by means of a post-effective
                  amendment any of the securities being registered that remain
                  unsold at the termination of the offering.

(2)      The Company hereby undertakes that, for purposes of determining any
liability under the Securities Act, each filing of the Company's annual report
pursuant to Section 13(a) or Section 15(d) of the Exchange Act that is
incorporated by reference in this 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
Company pursuant to the foregoing provisions, or otherwise, the Company has been
advised

                                       -3-
4

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 Company of expenses incurred or paid by a director, officer
or controlling person of the Company 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 Company 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.

                                       -4-
5

                                   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
-5-
6

                                  EXHIBIT INDEX

  Exhibits
  --------

      4             Hycor Biomedical Inc. 2000 Employee Stock Purchase Plan

      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)

                                       -6-