<PAGE>

As filed with the Securities and Exchange Commission on April 25, 2003

                                                    Registration No. 333-_______
--------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                                ----------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                               -------------------
                                IDEX CORPORATION
             (Exact name of registrant as specified in its charter)

DELAWARE                                                   36-3555336
(State or other jurisdiction of     ----------------       (I.R.S. Employer
incorporation or organization)                             Identification No.)

                           630 DUNDEE ROAD, SUITE 400
                            NORTHROOK, ILLINOIS 60062
                    (Address of principal executive offices)

                                 ---------------

              THIRD AMENDED AND RESTATED 1996 STOCK OPTION PLAN FOR
                  NON-OFFICER KEY EMPLOYEES OF IDEX CORPORATION

                            (full title of the plan)

                                 ---------------
                                                     Copy to:
   WAYNE P. SAYATOVIC                                CHRISTOPHER LUEKING
   Senior Vice President - Finance,                  Latham & Watkins
   Chief Financial Officer and Secretary             Sears Tower, Suite 5800
   IDEX Corporation                                  Chicago, Illinois 60606
   630 Dundee Road, Suite 400                        (312) 876-7700
   Northbrook, Illinois  60062                       Counsel to Registrant
   (847) 498-7070

                               -------------------
                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
=====================================================================================================================
Title of Each Class of                   Amount to be      Proposed Maximum    Proposed Maximum    Amount of
Securities to be Registered              Registered (1)    Offering Price      Aggregate           Registration
                                                           Per Share (2)       Offering Price(2)   Fee
---------------------------------------------------------------------------------------------------------------------
<S>                                      <C>               <C>                 <C>                 <C>
Common Stock, par value $.01 per share   1,000,000 shares  $31.94              $31,940,000         $2,584
---------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)     The Third Amended and Restated 1996 Stock Option Plan for Non-Officer
        Key Employees of IDEX Corporation (the "Plan") authorizes the issuance
        of a maximum of 3,200,000 shares of common stock of IDEX Corporation
        (the "Company") plus substitutions or adjustments to shares to account
        for any change in corporate capitalization, such as a stock split, any
        merger, consolidation, recapitalization or other distribution of stock
        or property of which 2,200,000 shares have already been registered on
        December 23, 1996 pursuant to Form S-8 Registration No. 333-18643 after
        giving affect to certain stock splits and on September 28, 2001 pursuant
        to Form S-8 Registration No. 333-70452 and on January 31, 2003 pursuant
        to Form S-8 Registration No. 333-102882. Only the 1,000,000 newly
        authorized shares under the Plan are being registered hereunder.

(2)     Estimated solely for purposes of computing the registration fee for the
        1,000,000 additional shares being registered hereunder. Pursuant to Rule
        457(c), the proposed Maximum Offering Price Per Share is based on the
        average of the high and low trading prices of the Company's common stock
        on the New York Stock Exchange on April 24, 2003, which was $31.94 per
        share.

<PAGE>

                           ---------------------------

        Pursuant to Rule 429, the prospectus that is part of this Registration
Statement also relates to Registration Statement Nos. 333-102882, 333-70452 and
333-18643.


<PAGE>

                                EXPLANATORY NOTE

        This Registration Statement covers 1,000,000 additional shares of our
common stock reserved for issuance under the Third Amended and Restated 1996
Stock Option Plan for Non-Officer Key Employees of IDEX Corporation (the
"Plan"). Our Board of Directors approved on January 29, 2003 and our
stockholders approved on March 25, 2003 the Plan which increased the number of
shares reserved for issuance thereunder to 3,200,000 shares. On December 23,
1996 we filed with the Securities and Exchange Commission (the "Commission")
Form S-8 Registration Statement No. 333-18643 (the "1996 Prior Registration
Statement"), covering an aggregate of 800,000 shares issuable under the Plan,
which had increased to an aggregate of 1,200,000 shares after giving effect to
stock splits. On September 28, 2001 we filed with the Commission Form S-8
Registration Statement No. 333-70452 (the "2001 Prior Registration Statement"),
covering an additional 450,000 shares. On January 31, 2003 we filed with the
Commission Form S-8 Registration Statement No. 333-102882 (the "2002 Prior
Registration Statement" and together with the 1996 Prior Registration Statement
and the 2001 Prior Registration Statement, the "Prior Registration Statements"),
covering an additional 550,000 shares. The contents of the Prior Registration
Statements are incorporated by reference herein to the extent not modified or
superseded thereby or by any subsequently filed document which is incorporated
by reference herein or therein. The Items below contain information required in
this registration that was not included in the Prior Registration Statements.


                                     PART I

ITEM 1.         PLAN INFORMATION

        Not required to be filed with this Registration Statement.

ITEM 2.         REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION

        Not required to be filed with this Registration Statement.

                                     PART II

ITEM 3.         INCORPORATION OF DOCUMENTS BY REFERENCE

        The documents listed below have been filed by the Company with the
Commission and are incorporated in this Registration Statement by reference:

                a.      The Company's Annual Report on Form 10-K for the fiscal
        year ended December 31, 2002, filed on February 28, 2003;

                b.      The Company's Proxy Statement, filed on March 5, 2003;

                c.      All other reports filed by us pursuant to Sections 13(a)
        or 15(d) of the Securities Exchange Act of 1934 since the end of our
        fiscal year ended December 31, 2002; and

<PAGE>

                d.      The description of the Company's Common Stock contained
        in our Registration Statement on Form 8-A filed on April 19, 1996 (File
        No. 1-10235) pursuant to Section 12 of the Securities Exchange Act of
        1934.

        All documents filed by the Company pursuant to Section 13(a), 13(c), 14
and 15(d) of the Securities Exchange Act of 1934 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 part
hereof from the date of filing 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 that also is or is
deemed to be incorporated by reference herein, modifies or supersedes such
statement. Any statement so modified or superseded shall not be deemed, except
as so modified or superseded, to constitute a part of this Registration
Statement.

ITEM 5.         INTERESTS OF NAMED EXPERTS AND COUNSEL

        Not applicable.

ITEM 8.         EXHIBITS

        See EXHIBIT INDEX.




<PAGE>

                                   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 Northbrook, state of Illinois, on this 25th day of
April, 2003.




                                           IDEX CORPORATION


                                           By: /s/ Wayne P. Sayatovic
                                              ---------------------------------
                                           Wayne P. Sayatovic
                                           Senior Vice President - Finance and
                                           Chief Financial Officer





                                POWER OF ATTORNEY

        KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Dennis K. Williams and Wayne P. Sayatovic or
either of them, his true and lawful attorney-in-fact and agent, with full power
of substitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all amendments or supplements to this Registration
Statement and to file the same with all exhibits thereto, and other documents in
connection therewith, with the Securities and Exchange Commission, granting unto
said attorney-in-fact and agent full power and authority to do and perform each
and every act and thing requisite and ratifying and confirming all that said
attorney-in-fact and agent or his substitute or substitutes may lawfully do or
cause to be done by virtue hereof.



<PAGE>

Pursuant to the requirements of the Securities Act of 1933, as amended, this
registration statement has been signed by the following persons in the
capacities and on the date indicated.

<TABLE>
<CAPTION>

SIGNATURES                              TITLES                          DATE
----------                              ------                          ----
<S>                                     <C>                             <C>

   /s/ Dennis K. Williams               Chairman of the Board of        April 25, 2003
----------------------------            Directors, President and
   Dennis K. Williams                   Chief Executive Officer
                                        (Principal Executive
                                        Officer) and Director


   /s/ Wayne P. Sayatovic               Senior Vice President -         April 25, 2003
----------------------------            Finance and Chief
   Wayne P. Sayatovic                   Financial Officer
                                        (Principal Financial and
                                        Accounting Officer)


   /s/ Bradley J. Bell                  Director                        April 25, 2003
----------------------------
   Bradley J. Bell

   /s/ Gregory B. Kenny                 Director                        April 25, 2003
----------------------------
   Gregory B. Kenny

   /s/ Paul E. Raether                  Director                        April 25, 2003
----------------------------
   Paul E. Raether

   /s/ Neil A. Springer                 Director                        April 25, 2003
----------------------------
   Neil A. Springer

   /s/ Michael T. Tokarz                Director                        April 25, 2003
----------------------------
   Michael T. Tokarz
</TABLE>




<PAGE>

IDEX CORPORATION
EXHIBIT INDEX

<TABLE>
<CAPTION>
EXHIBIT
NUMBER         DESCRIPTION OF EXHIBIT
------         ----------------------
<S>            <C>
4.1            Third Amended And Restated 1996 Stock Option Plan For
               Non-Officer Key Employees Of IDEX Corporation

5.1            Opinion and Consent of Latham & Watkins

23.1           Consent of Independent Auditors

23.2           Consent of Latham & Watkins (included in their opinion
               filed as Exhibit 5.1)

24.1           Power of Attorney (included in the signature page to the
               Registration Statement)
</TABLE>
[{"type": "S-8", "sequence": "1", "filename": "c76515sv8.txt", "description": "REGISTRATION STATEMENT", "secsgml_size_bytes": 12822}]
{"company-data": {"conformed-name": "IDEX CORP /DE/", "cik": "0000832101", "assigned-sic": "3561", "irs-number": "363555336", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-104768", "film-number": "03665257"}, "business-address": {"street1": "630 DUNDEE RD STE 400", "city": "NORTHBROOK", "state": "IL", "zip": "60062", "phone": "8474987070"}}
As filed with the Securities and Exchange Commission on April 25, 2003

                                                    Registration No. 333-_______
--------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                                ----------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                               -------------------
                                IDEX CORPORATION
             (Exact name of registrant as specified in its charter)

DELAWARE                                                   36-3555336
(State or other jurisdiction of     ----------------       (I.R.S. Employer
incorporation or organization)                             Identification No.)

                           630 DUNDEE ROAD, SUITE 400
                            NORTHROOK, ILLINOIS 60062
                    (Address of principal executive offices)

                                 ---------------

              THIRD AMENDED AND RESTATED 1996 STOCK OPTION PLAN FOR
                  NON-OFFICER KEY EMPLOYEES OF IDEX CORPORATION

                            (full title of the plan)

                                 ---------------
                                                     Copy to:
   WAYNE P. SAYATOVIC                                CHRISTOPHER LUEKING
   Senior Vice President - Finance,                  Latham & Watkins
   Chief Financial Officer and Secretary             Sears Tower, Suite 5800
   IDEX Corporation                                  Chicago, Illinois 60606
   630 Dundee Road, Suite 400                        (312) 876-7700
   Northbrook, Illinois  60062                       Counsel to Registrant
   (847) 498-7070

                               -------------------
                         CALCULATION OF REGISTRATION FEE
=====================================================================================================================
Title of Each Class of                   Amount to be      Proposed Maximum    Proposed Maximum    Amount of
Securities to be Registered              Registered (1)    Offering Price      Aggregate           Registration
                                                           Per Share (2)       Offering Price(2)   Fee
---------------------------------------------------------------------------------------------------------------------
Common Stock, par value $.01 per share   1,000,000 shares  $31.94              $31,940,000         $2,584
---------------------------------------------------------------------------------------------------------------------
(1)     The Third Amended and Restated 1996 Stock Option Plan for Non-Officer
        Key Employees of IDEX Corporation (the "Plan") authorizes the issuance
        of a maximum of 3,200,000 shares of common stock of IDEX Corporation
        (the "Company") plus substitutions or adjustments to shares to account
        for any change in corporate capitalization, such as a stock split, any
        merger, consolidation, recapitalization or other distribution of stock
        or property of which 2,200,000 shares have already been registered on
        December 23, 1996 pursuant to Form S-8 Registration No. 333-18643 after
        giving affect to certain stock splits and on September 28, 2001 pursuant
        to Form S-8 Registration No. 333-70452 and on January 31, 2003 pursuant
        to Form S-8 Registration No. 333-102882. Only the 1,000,000 newly
        authorized shares under the Plan are being registered hereunder.

(2)     Estimated solely for purposes of computing the registration fee for the
        1,000,000 additional shares being registered hereunder. Pursuant to Rule
        457(c), the proposed Maximum Offering Price Per Share is based on the
        average of the high and low trading prices of the Company's common stock
        on the New York Stock Exchange on April 24, 2003, which was $31.94 per
        share.
---------------------------

        Pursuant to Rule 429, the prospectus that is part of this Registration
Statement also relates to Registration Statement Nos. 333-102882, 333-70452 and
333-18643.
EXPLANATORY NOTE

        This Registration Statement covers 1,000,000 additional shares of our
common stock reserved for issuance under the Third Amended and Restated 1996
Stock Option Plan for Non-Officer Key Employees of IDEX Corporation (the
"Plan"). Our Board of Directors approved on January 29, 2003 and our
stockholders approved on March 25, 2003 the Plan which increased the number of
shares reserved for issuance thereunder to 3,200,000 shares. On December 23,
1996 we filed with the Securities and Exchange Commission (the "Commission")
Form S-8 Registration Statement No. 333-18643 (the "1996 Prior Registration
Statement"), covering an aggregate of 800,000 shares issuable under the Plan,
which had increased to an aggregate of 1,200,000 shares after giving effect to
stock splits. On September 28, 2001 we filed with the Commission Form S-8
Registration Statement No. 333-70452 (the "2001 Prior Registration Statement"),
covering an additional 450,000 shares. On January 31, 2003 we filed with the
Commission Form S-8 Registration Statement No. 333-102882 (the "2002 Prior
Registration Statement" and together with the 1996 Prior Registration Statement
and the 2001 Prior Registration Statement, the "Prior Registration Statements"),
covering an additional 550,000 shares. The contents of the Prior Registration
Statements are incorporated by reference herein to the extent not modified or
superseded thereby or by any subsequently filed document which is incorporated
by reference herein or therein. The Items below contain information required in
this registration that was not included in the Prior Registration Statements.

                                     PART I

ITEM 1.         PLAN INFORMATION

        Not required to be filed with this Registration Statement.

ITEM 2.         REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION

        Not required to be filed with this Registration Statement.

                                     PART II

ITEM 3.         INCORPORATION OF DOCUMENTS BY REFERENCE

        The documents listed below have been filed by the Company with the
Commission and are incorporated in this Registration Statement by reference:

                a.      The Company's Annual Report on Form 10-K for the fiscal
        year ended December 31, 2002, filed on February 28, 2003;

                b.      The Company's Proxy Statement, filed on March 5, 2003;

                c.      All other reports filed by us pursuant to Sections 13(a)
        or 15(d) of the Securities Exchange Act of 1934 since the end of our
        fiscal year ended December 31, 2002; and
d.      The description of the Company's Common Stock contained
        in our Registration Statement on Form 8-A filed on April 19, 1996 (File
        No. 1-10235) pursuant to Section 12 of the Securities Exchange Act of
        1934.

        All documents filed by the Company pursuant to Section 13(a), 13(c), 14
and 15(d) of the Securities Exchange Act of 1934 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 part
hereof from the date of filing 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 that also is or is
deemed to be incorporated by reference herein, modifies or supersedes such
statement. Any statement so modified or superseded shall not be deemed, except
as so modified or superseded, to constitute a part of this Registration
Statement.

ITEM 5.         INTERESTS OF NAMED EXPERTS AND COUNSEL

        Not applicable.

ITEM 8.         EXHIBITS

        See EXHIBIT INDEX.
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 Northbrook, state of Illinois, on this 25th day of
April, 2003.

                                           IDEX CORPORATION

                                           By: /s/ Wayne P. Sayatovic
                                              ---------------------------------
                                           Wayne P. Sayatovic
                                           Senior Vice President - Finance and
                                           Chief Financial Officer

                                POWER OF ATTORNEY

        KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Dennis K. Williams and Wayne P. Sayatovic or
either of them, his true and lawful attorney-in-fact and agent, with full power
of substitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all amendments or supplements to this Registration
Statement and to file the same with all exhibits thereto, and other documents in
connection therewith, with the Securities and Exchange Commission, granting unto
said attorney-in-fact and agent full power and authority to do and perform each
and every act and thing requisite and ratifying and confirming all that said
attorney-in-fact and agent or his substitute or substitutes may lawfully do or
cause to be done by virtue hereof.
Pursuant to the requirements of the Securities Act of 1933, as amended, this
registration statement has been signed by the following persons in the
capacities and on the date indicated.
SIGNATURES                              TITLES                          DATE
----------                              ------                          ----
/s/ Dennis K. Williams               Chairman of the Board of        April 25, 2003
----------------------------            Directors, President and
   Dennis K. Williams                   Chief Executive Officer
                                        (Principal Executive
                                        Officer) and Director

   /s/ Wayne P. Sayatovic               Senior Vice President -         April 25, 2003
----------------------------            Finance and Chief
   Wayne P. Sayatovic                   Financial Officer
                                        (Principal Financial and
                                        Accounting Officer)

   /s/ Bradley J. Bell                  Director                        April 25, 2003
----------------------------
   Bradley J. Bell

   /s/ Gregory B. Kenny                 Director                        April 25, 2003
----------------------------
   Gregory B. Kenny

   /s/ Paul E. Raether                  Director                        April 25, 2003
----------------------------
   Paul E. Raether

   /s/ Neil A. Springer                 Director                        April 25, 2003
----------------------------
   Neil A. Springer

   /s/ Michael T. Tokarz                Director                        April 25, 2003
----------------------------
   Michael T. Tokarz
IDEX CORPORATION
EXHIBIT INDEX
EXHIBIT
NUMBER         DESCRIPTION OF EXHIBIT
------         ----------------------
4.1            Third Amended And Restated 1996 Stock Option Plan For
               Non-Officer Key Employees Of IDEX Corporation

5.1            Opinion and Consent of Latham & Watkins

23.1           Consent of Independent Auditors

23.2           Consent of Latham & Watkins (included in their opinion
               filed as Exhibit 5.1)

24.1           Power of Attorney (included in the signature page to the
               Registration Statement)