<PAGE>   1
As filed with the Securities and Exchange Commission on August 12, 1996. Subject
                                 to amendment.

                                                       Registration No. 33-
================================================================================


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                  ISOMEDIX INC.
               (Exact name of issuer as specified in its charter)

         DELAWARE                                                22-1986189
(State or other jurisdic-                                     (I.R.S. Employer
  tion of incorporation                                      Identification No.)
     or organization)


                                 11 Apollo Drive
                           Whippany, New Jersey 07981
                    (Address of principal executive offices)


                                  ISOMEDIX INC.
                          1996 LONG TERM INCENTIVE PLAN

                                   PETER MAYER
                             Chief Executive Officer
                                 11 Apollo Drive
                           Whippany, New Jersey 07981
                                 (201) 887-4700
                      (Name, address and telephone number,
                   including area code, of agent for service)


                                    Copy to:

                             THOMAS M. HAYTHE, Esq.
                                 Haythe & Curley
                                 237 Park Avenue
                            New York, New York 10017


        Approximate date of commencement of proposed sale to the public:
                        As soon as practicable after the
                    Registration Statement becomes effective.


                         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*         price*          fee
 ----------        ----------      ----------         ------          ---
                                                                    
<S>                  <C>            <C>            <C>             <C>      
Common Stock         350,000        $14.0625       $4,921,875      $1,697.20
($.01 par            shares                                    
value)                                                         
</TABLE>                                                         
================================================================================

*Estimated solely for purposes of calculating the registration fee on the basis
of the average of the high and low sales prices of the Common Stock on August 8,
1996, as reported on the New York Stock Exchange.
================================================================================


<PAGE>   2
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


Item 3.  Incorporation of Documents by Reference.

                  The Company hereby states that (i) the documents listed in (a)
through (c) below are incorporated by reference in this Registration Statement
and (ii) all documents subsequently filed by the Company pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as amended,
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 in this
Registration Statement and to be a part hereof from the date of filing of such
documents.

                  (a) The Company's Annual Report on Form 10-K for the year
ended December 31, 1995.

                  (b) The Company's Quarterly Report on Form 10-Q for the
quarter ended March 31, 1996.

                  (c) The description of the Company's Common Stock contained in
the Company's Registration Statement on Form 8- A (number 113622), filed on
February 7, 1995.

Item 4.           Description of Securities.

                  Not applicable.

Item 5.           Interests of Named Experts and Counsel.

                  Thomas M. Haythe, a partner in the law firm of Haythe &
Curley, the Company's counsel in connection with the offering, is a director,
officer and stockholder of this Company.

Item 6.           Indemnification of Directors and Officers.

                  Under the provisions of Article SEVENTH of the Certificate of
Incorporation of the Company, as permitted by Section 145 of the General
Corporation Law of the State of Delaware, the Company is required to indemnify a
director or officer of the Company for expenses arising out of legal proceedings
in which the director or officer becomes involved by reason of his position as a
director or officer of the Company, if he acted in good faith and in a manner he





                                      II-1

<PAGE>   3







reasonable believed to be in or not opposed to the best interests of the Company
and, with respect to any criminal proceedings, if he had no reasonable cause to
believe his conduct was unlawful. Expenses against which a director or officer
of the Company may be indemnified include amounts paid in satisfaction of
settlements, judgments, fines and other expenses (including attorneys' fees)
incurred in connection with such proceedings. In a proceeding to procure a
judgment in the Company's favor, a director or officer may be indemnified for
expenses incurred by him in connection with the defense or settlement of the
suit if he acted in good faith and in a manner he reasonably believed to be in
or not opposed to the best interests of the Company, except that no
indemnification shall be permitted without a court order in respect of any
claim, issue, or matter as to which such director or officer shall have been
adjudged to be liable for negligence or misconduct in the performance of his
duty to the Company. Indemnification of a director or officer as provided above,
unless court-ordered, shall be made by the Company only upon a determination
that indemnification is proper in a specific case. Such determination shall be
made (i) by a vote of the majority of directors who were not parties to the
proceeding involved, (ii) by independent legal counsel in a written opinion or
(iii) by the stockholders of the Company.

Item 7.           Exemption from Registration Claimed.

                  Not applicable.

Item 8.           Exhibits.

                  The Exhibits required to be filed as part of this Registration
Statement are listed in the attached Index to Exhibits.

Item 9.           Undertakings.

                  The undersigned Registrant hereby undertakes, except as
otherwise specifically provided in the rules of the Securities and Exchange
Commission promulgated under the Securities Act of 1933:

                  (1) To file, during any period in which offers or sales are
being made, a post-effective amendment to this Registration Statement:

                  (i) To include any prospectus required by section 10(a)(3) of
the Securities Act of 1933;






                                      II-2

<PAGE>   4







             (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 hereof) 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 paragraphs (1)(i) and (1)(ii) do not apply if this
Registration Statement is on Form S-3 or Form S-8 and the information required
to be included in a post-effective amendment by those paragraphs is contained in
periodic reports filed by the Registrant pursuant to section 13 or section 15(d)
of the Securities Exchange Act of 1934 that are incorporated by reference in
this Registration Statement;

                  (2) That, for the purpose of determining any liability under
the Securities Act of 1933, each such post-effective amendment shall be deemed
to be a new registration statement relating to the securities offered therein,
and the offering of such securities at that time shall be deemed to be the
initial bona fide offering thereof; and

                  (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

                  The undersigned Registrant hereby undertakes that, for
purposes of determining any liability under the Securities Act of 1933, each
filing of the Registrant's annual report pursuant to section 13(a) or section
15(d) of the Securities Exchange Act of 1934 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.

                  Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such





                                      II-3

<PAGE>   5







indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Act and will be governed by the final adjudication of
such issue.







                                      II-4

<PAGE>   6







                                POWER OF ATTORNEY

                  The Registrant and each person whose signature appears below
hereby appoints Peter Mayer and Thomas J. DeAngelo as attorneys-in-fact with
full power of substitution, severally, to execute in the name and on behalf of
the Registrant and each such person, individually and in each capacity stated
below, one or more amendments (including post-effective amendments) to this
Registration Statement as the attorney-in-fact acting in the premises deems
appropriate and to file any such amendment to this Registration Statement with
the Securities and Exchange Commission.

                                   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 Whippany and State of New Jersey on the 8th day
of August, 1996.

                                                     ISOMEDIX INC.              
                                                     
                                                     
                                                     By: /s/ Peter Mayer
                                                         -----------------------
                                                         Peter Mayer
                                                         Chief Executive Officer
                               

                  Pursuant to the requirements of the Securities Act of 1933,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.



<TABLE>
<CAPTION>
           Signature                            Title                                       Date
           ---------                            -----                                       ----



<S>                                           <C>                                      <C>
/s/ Peter Mayer                               President, Chief                         August 8, 1996
- ----------------------                        Executive Officer
Peter Mayer                                   and Director     


/s/ John Masefield                            Chairman of the                          August 8, 1996
- ----------------------                        Board and Director
John Masefield                                                   
</TABLE>






                                      II-5

<PAGE>   7
<TABLE>
<CAPTION>
           Signature                            Title                                       Date
           ---------                            -----                                       ----



<S>                                           <C>                                      <C>
/s/ Thomas J. DeAngelo                        Vice President                           August 8, 1996
- ----------------------                        Finance and
Thomas J. DeAngelo                            Administration,
                                              Secretary, Treasurer,
                                              Principal Financial
                                              Officer and Principal
                                              Accounting Officer,
                                              and Director

/s/ H. Stuart Campbell                        Director                                 August 8, 1996
- ----------------------
H. Stuart Campbell


/s/ Thomas M. Haythe                          Director                                 August 8, 1996
- ----------------------
Thomas M. Haythe


/s/ David M. Lank                             Director                                 August 8, 1996
- ----------------------
David M. Lank


                                              Director                                 August __, 1996
- ----------------------
Elmer A. Sticco
</TABLE>








                                      II-6

<PAGE>   8







                               CONSENT OF COUNSEL


                  The consent of Haythe & Curley is contained in their opinion
filed as Exhibit 5 to this Registration Statement.






                                      II-7

<PAGE>   9

                       CONSENT OF INDEPENDENT ACCOUNTANTS


We consent to the incorporation by reference in the Registration Statement of
Isomedix Inc. on Form S-8 of our report dated February 16, 1996, on our audits
of the consolidated financial statements and financial statement schedules of
Isomedix Inc. and Subsidiaries as of December 31, 1995 and 1994, and for the
years ended December 31, 1995, 1994, and 1993, which report is included in the
Annual Report on Form 10-K.
                               


                                            COOPERS & LYBRAND L.L.P.

Parsippany, New Jersey
August 12, 1996






<PAGE>   10







                                INDEX TO EXHIBITS


<TABLE>
<CAPTION>
      Number                  Description of Exhibit                                              Page
      ------                  ----------------------                                              ----

<S>                           <C>                                                              <C>
 4(i)                -        Isomedix Inc. 1996 Long Term
                              Incentive Plan

 5                   -        Opinion of Haythe & Curley

 23(i)               -        Consent of Coopers & Lybrand                                         --
                              L.L.P., Independent Accountants
                              (See "Consent of Independent
                              Accountants" in the Registration
                              Statement)

 23(ii)              -        Consent of Haythe & Curley                                           --
                              (contained in Exhibit 5)

 24                  -        Power of Attorney (See "Power of                                     --
                              Attorney" in the Registration
                              Statement)
</TABLE>
[{"type": "S-8", "sequence": "1", "description": "FORM S-8 -- ISOMEDIX INC.", "secsgml_size_bytes": 17592}]
{"company-data": {"conformed-name": "ISOMEDIX INC", "cik": "0000719522", "assigned-sic": "7389", "irs-number": "221986189", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-10033", "film-number": "96609442"}, "business-address": {"street1": "11 APOLLO DR", "city": "WHIPPANY", "state": "NJ", "zip": "07981", "phone": "2018874700"}, "mail-address": {"street1": "11 APOLLO DR", "city": "WHIPPANY", "state": "NJ", "zip": "07981"}}
1
As filed with the Securities and Exchange Commission on August 12, 1996. Subject
                                 to amendment.

                                                       Registration No. 33-
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                  ISOMEDIX INC.
               (Exact name of issuer as specified in its charter)

         DELAWARE                                                22-1986189
(State or other jurisdic-                                     (I.R.S. Employer
  tion of incorporation                                      Identification No.)
     or organization)

                                 11 Apollo Drive
                           Whippany, New Jersey 07981
                    (Address of principal executive offices)

                                  ISOMEDIX INC.
                          1996 LONG TERM INCENTIVE PLAN

                                   PETER MAYER
                             Chief Executive Officer
                                 11 Apollo Drive
                           Whippany, New Jersey 07981
                                 (201) 887-4700
                      (Name, address and telephone number,
                   including area code, of agent for service)

                                    Copy to:

                             THOMAS M. HAYTHE, Esq.
                                 Haythe & Curley
                                 237 Park Avenue
                            New York, New York 10017

        Approximate date of commencement of proposed sale to the public:
                        As soon as practicable after the
                    Registration Statement becomes effective.

                         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*         price*          fee
 ----------        ----------      ----------         ------          ---
Common Stock         350,000        $14.0625       $4,921,875      $1,697.20
($.01 par            shares                                    
value)
================================================================================

*Estimated solely for purposes of calculating the registration fee on the basis
of the average of the high and low sales prices of the Common Stock on August 8,
1996, as reported on the New York Stock Exchange.
================================================================================
2
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Documents by Reference.

                  The Company hereby states that (i) the documents listed in (a)
through (c) below are incorporated by reference in this Registration Statement
and (ii) all documents subsequently filed by the Company pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as amended,
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 in this
Registration Statement and to be a part hereof from the date of filing of such
documents.

                  (a) The Company's Annual Report on Form 10-K for the year
ended December 31, 1995.

                  (b) The Company's Quarterly Report on Form 10-Q for the
quarter ended March 31, 1996.

                  (c) The description of the Company's Common Stock contained in
the Company's Registration Statement on Form 8- A (number 113622), filed on
February 7, 1995.

Item 4.           Description of Securities.

                  Not applicable.

Item 5.           Interests of Named Experts and Counsel.

                  Thomas M. Haythe, a partner in the law firm of Haythe &
Curley, the Company's counsel in connection with the offering, is a director,
officer and stockholder of this Company.

Item 6.           Indemnification of Directors and Officers.

                  Under the provisions of Article SEVENTH of the Certificate of
Incorporation of the Company, as permitted by Section 145 of the General
Corporation Law of the State of Delaware, the Company is required to indemnify a
director or officer of the Company for expenses arising out of legal proceedings
in which the director or officer becomes involved by reason of his position as a
director or officer of the Company, if he acted in good faith and in a manner he

                                      II-1
3

reasonable believed to be in or not opposed to the best interests of the Company
and, with respect to any criminal proceedings, if he had no reasonable cause to
believe his conduct was unlawful. Expenses against which a director or officer
of the Company may be indemnified include amounts paid in satisfaction of
settlements, judgments, fines and other expenses (including attorneys' fees)
incurred in connection with such proceedings. In a proceeding to procure a
judgment in the Company's favor, a director or officer may be indemnified for
expenses incurred by him in connection with the defense or settlement of the
suit if he acted in good faith and in a manner he reasonably believed to be in
or not opposed to the best interests of the Company, except that no
indemnification shall be permitted without a court order in respect of any
claim, issue, or matter as to which such director or officer shall have been
adjudged to be liable for negligence or misconduct in the performance of his
duty to the Company. Indemnification of a director or officer as provided above,
unless court-ordered, shall be made by the Company only upon a determination
that indemnification is proper in a specific case. Such determination shall be
made (i) by a vote of the majority of directors who were not parties to the
proceeding involved, (ii) by independent legal counsel in a written opinion or
(iii) by the stockholders of the Company.

Item 7.           Exemption from Registration Claimed.

                  Not applicable.

Item 8.           Exhibits.

                  The Exhibits required to be filed as part of this Registration
Statement are listed in the attached Index to Exhibits.

Item 9.           Undertakings.

                  The undersigned Registrant hereby undertakes, except as
otherwise specifically provided in the rules of the Securities and Exchange
Commission promulgated under the Securities Act of 1933:

                  (1) To file, during any period in which offers or sales are
being made, a post-effective amendment to this Registration Statement:

                  (i) To include any prospectus required by section 10(a)(3) of
the Securities Act of 1933;

                                      II-2
4

             (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 hereof) 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 paragraphs (1)(i) and (1)(ii) do not apply if this
Registration Statement is on Form S-3 or Form S-8 and the information required
to be included in a post-effective amendment by those paragraphs is contained in
periodic reports filed by the Registrant pursuant to section 13 or section 15(d)
of the Securities Exchange Act of 1934 that are incorporated by reference in
this Registration Statement;

                  (2) That, for the purpose of determining any liability under
the Securities Act of 1933, each such post-effective amendment shall be deemed
to be a new registration statement relating to the securities offered therein,
and the offering of such securities at that time shall be deemed to be the
initial bona fide offering thereof; and

                  (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

                  The undersigned Registrant hereby undertakes that, for
purposes of determining any liability under the Securities Act of 1933, each
filing of the Registrant's annual report pursuant to section 13(a) or section
15(d) of the Securities Exchange Act of 1934 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.

                  Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such

                                      II-3
5

indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Act and will be governed by the final adjudication of
such issue.

                                      II-4
6

                                POWER OF ATTORNEY

                  The Registrant and each person whose signature appears below
hereby appoints Peter Mayer and Thomas J. DeAngelo as attorneys-in-fact with
full power of substitution, severally, to execute in the name and on behalf of
the Registrant and each such person, individually and in each capacity stated
below, one or more amendments (including post-effective amendments) to this
Registration Statement as the attorney-in-fact acting in the premises deems
appropriate and to file any such amendment to this Registration Statement with
the Securities and Exchange Commission.

                                   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 Whippany and State of New Jersey on the 8th day
of August, 1996.

                                                     ISOMEDIX INC.              
                                                     
                                                     
                                                     By: /s/ Peter Mayer
                                                         -----------------------
                                                         Peter Mayer
                                                         Chief Executive Officer
                               

                  Pursuant to the requirements of the Securities Act of 1933,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.
Signature                            Title                                       Date
           ---------                            -----                                       ----
/s/ Peter Mayer                               President, Chief                         August 8, 1996
- ----------------------                        Executive Officer
Peter Mayer                                   and Director     

/s/ John Masefield                            Chairman of the                          August 8, 1996
- ----------------------                        Board and Director
John Masefield
II-5
7
Signature                            Title                                       Date
           ---------                            -----                                       ----
/s/ Thomas J. DeAngelo                        Vice President                           August 8, 1996
- ----------------------                        Finance and
Thomas J. DeAngelo                            Administration,
                                              Secretary, Treasurer,
                                              Principal Financial
                                              Officer and Principal
                                              Accounting Officer,
                                              and Director

/s/ H. Stuart Campbell                        Director                                 August 8, 1996
- ----------------------
H. Stuart Campbell

/s/ Thomas M. Haythe                          Director                                 August 8, 1996
- ----------------------
Thomas M. Haythe

/s/ David M. Lank                             Director                                 August 8, 1996
- ----------------------
David M. Lank

                                              Director                                 August __, 1996
- ----------------------
Elmer A. Sticco
II-6
8

                               CONSENT OF COUNSEL

                  The consent of Haythe & Curley is contained in their opinion
filed as Exhibit 5 to this Registration Statement.

                                      II-7
9

                       CONSENT OF INDEPENDENT ACCOUNTANTS

We consent to the incorporation by reference in the Registration Statement of
Isomedix Inc. on Form S-8 of our report dated February 16, 1996, on our audits
of the consolidated financial statements and financial statement schedules of
Isomedix Inc. and Subsidiaries as of December 31, 1995 and 1994, and for the
years ended December 31, 1995, 1994, and 1993, which report is included in the
Annual Report on Form 10-K.
                               

                                            COOPERS & LYBRAND L.L.P.

Parsippany, New Jersey
August 12, 1996
10

                                INDEX TO EXHIBITS
Number                  Description of Exhibit                                              Page
      ------                  ----------------------                                              ----
4(i)                -        Isomedix Inc. 1996 Long Term
                              Incentive Plan

 5                   -        Opinion of Haythe & Curley

 23(i)               -        Consent of Coopers & Lybrand                                         --
                              L.L.P., Independent Accountants
                              (See "Consent of Independent
                              Accountants" in the Registration
                              Statement)

 23(ii)              -        Consent of Haythe & Curley                                           --
                              (contained in Exhibit 5)

 24                  -        Power of Attorney (See "Power of                                     --
                              Attorney" in the Registration
                              Statement)