EXHIBIT 5.1


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        IDEX Corporation
        630 Dundee Road, Suite 400
        Northbrook, Illinois 60062

                     Re:    Registration Statement on Form S-8 with respect to
                            1,000,000 shares of Common Stock, par value $.01 per
                            share

        Ladies and Gentlemen:

                In connection with the preparation and filing by IDEX
        Corporation, a Delaware corporation (the "Company"), with the Securities
        and Exchange Commission (the "Commission") under the Securities Act of
        1933, as amended (the "Act"), of a Registration Statement on Form S-8
        (the "Registration Statement") relating to the issuance by the Company
        of 1,000,000 shares of the Company's Common Stock, par value $.01 per
        share (the "Shares"), pursuant to the exercise of options granted or to
        be granted under the Third Amended and Restated 1996 Stock Option Plan
        for Non-Officer Key Employees of IDEX Corporation (the "Key Employees
        Plan"), you have requested our opinion with respect to the matters set
        forth below.

                In our capacity as your counsel in connection with such
        registration, we are familiar with the proceedings taken by the Company
        in connection with the authorization, issuance and sale of the Shares.
        In addition, we have made such legal and factual examinations and
        inquiries, including an examination of originals or copies certified or
        otherwise identified to our satisfaction of such documents, corporate
        records and instruments, as we have deemed necessary or appropriate for
        purposes of this opinion.

                In our examination, we have assumed the genuineness of all
        signatures, the authenticity of all documents submitted to us as
        originals and the conformity to authentic original documents of all
        documents submitted to us as copies.

                We are opining herein as to the effect on the subject
        transaction only of the General Corporation Law of the State of
        Delaware, and we express no opinion with respect to the applicability
        thereto, or the




EXHIBIT 5.1
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        effect thereon, of the laws of any other jurisdiction or any other
        Delaware laws, or as to any matters of municipal law or the laws of any
        local agency within any state.

                Subject to the foregoing, it is our opinion that the Shares have
        been duly authorized and, when issued and sold upon exercise of options
        for such Shares and payment of the exercise price therefore as
        contemplated by the Key Employees Plan, will be validly issued, fully
        paid and non-assessable.

                We consent to your filing this opinion as an exhibit to the
        Registration Statement.



                                                   Very truly yours,

                                                   /s/ Latham & Watkins LLP

                                                   Latham & Watkins LLP
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