<PAGE>

                                                    REGISTRATION  NO. 333-

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

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

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

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

                               INPUT/OUTPUT, INC.
             (Exact name of registrant as specified in its charter)

            DELAWARE                                    22-2286646
  (State or other jurisdiction           (I.R.S. Employer Identification Number)
of incorporation or organization)

                              12300 PARC CREST DR.
                              STAFFORD, TEXAS 77477
                                 (281) 933-3339
    (Address, including zip code, and telephone number, including area code,
                  of registrant's principal executive offices)

  INPUT/OUTPUT, INC.- CONCEPT SYSTEMS EMPLOYMENT INDUCEMENT STOCK OPTION PROGRAM
                              (Full title of plan)

                              DAVID L. ROLAND, ESQ.
                         VICE PRESIDENT-GENERAL COUNSEL
                             AND CORPORATE SECRETARY
                               INPUT/OUTPUT, INC.
                              12300 PARC CREST DR.
                              STAFFORD, TEXAS 77477
                                 (281) 933-3339
            (Name, address and telephone number of agent for service)

                                 WITH COPIES TO:
                           FULBRIGHT & JAWORSKI L.L.P.
                            1301 MCKINNEY, SUITE 5100
                              HOUSTON, TEXAS 77010
                          ATTENTION: MARC H. FOLLADORI
                                 (713) 651-5151

<Table>
<CAPTION>
                                           CALCULATION OF REGISTRATION FEE
======================================================================================================================
                                                      PROPOSED           PROPOSED MAXIMUM
   TITLE OF SECURITIES        AMOUNT TO           MAXIMUM OFFERING      AGGREGATE OFFERING          AMOUNT OF
    TO BE REGISTERED       BE REGISTERED(2)      PRICE PER SHARE(2)          PRICE(2)            REGISTRATION FEE
----------------------------------------------------------------------------------------------------------------------
<S>                        <C>                   <C>                    <C>                      <C>
   Common Stock
   $.01 par value(1)       365,000 shares              $8.32                $3,036,800                $384.76
======================================================================================================================
</TABLE>

   (1)  This Registration Statement also covers the associated rights to
        purchase Series A Preferred Stock, par value $0.01 per share, issued
        pursuant to that certain Rights Agreement dated as of January 17, 1997,
        by and between the registrant and Harris Trust and Savings Bank, as
        Rights Agent, as amended by the First Amendment
        to Rights Agreement, dated effective as of April 21, 1999.

   (2)  The 365,000 shares registered hereby represent shares issuable pursuant
        to the Input/Output, Inc.- Concept Systems Employment Inducement Stock
        Option Program, evidenced by stock option award agreements entered into
        between the registrant and the individual participants in such program.
        Pursuant to Rule 416(a), also registered hereunder is an indeterminate
        number of shares of common stock issuable as a result of certain
        anti-dilution provisions contained in those agreements. With respect to
        the shares registered hereby, the offering price per share, the
        aggregate offering price and the registration fee have been calculated
        in accordance with paragraphs (c) and (h)(1) of Rule 457 on the basis
        of the average high and low sale prices for the registrant's common
        stock on July 27, 2004 as reported on the New York Stock Exchange
        composite transactions ($8.32 per share).


<PAGE>


                             INTRODUCTORY STATEMENT

         On February 23, 2004, Input/Output, Inc., a Delaware corporation ("I/O"
or the "Registrant") entered into a Share Acquisition Agreement with certain
security holders of Concept Systems Holding Limited, a private limited company
under the laws of Scotland ("Concept"), to acquire all of the share capital of
Concept.

         As contemplated by the terms of such acquisition agreement, the
Registrant granted certain employees of Concept (and its subsidiaries)
employment inducement stock option awards as a material inducement to their
joining the Registrant, under a program known as the Input/Output, Inc. -
Concept Systems Employment Inducement Stock Option Program.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE

         The contents of the following documents, filed by the Registrant with
the U.S. Securities and Exchange Commission (the "Commission"), are incorporated
into this registration statement (the "Registration Statement") by reference:

         o    The Registrant's Annual Report on Form 10-K for the fiscal year
              ended December 31, 2003, filed with the Commission on March 12,
              2004 pursuant to Section 13(a) of the Securities Exchange Act of
              1934, as amended (the "Exchange Act"), as amended by Form
              10-K/A-1 filed with the Commission on April 23, 2004 and as
              further amended by Form 10-K/A-2 filed with the Commission on May
              10, 2004;

         o    The Registrant's Quarterly Report on Form 10-Q for the fiscal
              quarter ended March 31, 2004, filed with the Commission on May 10,
              2004 pursuant to Section 13(a) of the Exchange Act;

         o    The Registrant's Current Reports on Form 8-K filed with the
              Commission on March 5, May 3 and May 11, 2004 (as amended by Form
              8-K/A-1 and Form 8-K/A-2 filed with the Commission on May 28,
              2004 and June 15, 2004, respectively), pursuant to Section 13(a)
              of the Exchange Act;

         o    The description of the Registrant's common stock contained in the
              Registration Statement on Form 8-A filed with the Commission on
              October 17, 1994, filed under Section 12(b) of the Exchange Act,
              as amended by the Registrant's Current Report on Form 8-K filed on
              March 8, 2002; and

         o    The Registrant's Registration Statement on Form 8-A12B filed with
              the Commission on January 27, 1997, as amended by Form 8-A12B/A
              filed on May 7, 1999.

         All documents filed by the Registrant with the Commission pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act subsequent to the filing
date of this Registration Statement and prior to the filing of a post-effective
amendment to this Registration Statement which indicates that all securities
offered have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated into this Registration Statement by
reference and to be a part hereof from the date of filing of each such document.


                                      II-2
<PAGE>

ITEM 4.  DESCRIPTION OF SECURITIES

         Not applicable.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         Not applicable.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         The General Corporation Law of the State of Delaware ("DGCL") permits
the Registrant and its stockholders to limit directors' exposure to liability
for certain breaches of the directors' fiduciary duty. The Restated Certificate
of Incorporation of the Registrant, as amended (the "Charter"), provides that a
director of the Registrant shall not be personally liable to the Registrant or
its stockholders for monetary damages for breach of fiduciary duty as a
director, except for liability (i) for any breach of the director's duty of
loyalty to the Registrant or its stockholders, (ii) for acts or omissions not in
good faith or which involve intentional misconduct or a knowing violation of
law, (iii) under Section 174 of the DGCL or (iv) for any transaction from which
the director derived an improper personal benefit.

         The Amended and Restated Bylaws of the Registrant (the "Bylaws")
provide that the Registrant shall, to the full extent permitted by applicable
laws (including the DGCL), indemnify its directors, officers, employees and
agents with respect to expenses (including counsel fees), judgments, fines,
penalties and other liabilities and amounts incurred by any such person in
connection with any threatened, pending or completed action, suit or proceeding
to which such person is or was a party, or is or was threatened to be made a
party, by reason of the fact that such person is or was serving as a director,
officer, employee or agent of the Registrant or any of its direct or indirect
wholly owned subsidiaries, or is or was serving at the request of the Registrant
or any of its direct or indirect wholly owned subsidiaries as a director,
officer, employee, agent or trustee of another corporation, partnership, joint
venture, trust, employee benefit plan or other enterprise. The Bylaws provide
that the indemnification provided pursuant to the Bylaws is not exclusive of any
other rights to which those seeking indemnification may be entitled under any
provision of law, certificate of incorporation, bylaws, governing documents,
agreement, vote of stockholders or disinterested directors of the Registrant or
any of its direct or indirect wholly owned subsidiaries, or otherwise.

         The Registrant maintains a standard form of officers' and directors'
liability insurance policy which provides coverage to the officers and directors
of the Registrant for certain liabilities, including certain liabilities which
may arise out of this Registration Statement.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Not applicable.

ITEM 8.  EXHIBITS

         4.1      Form of Input/Output, Inc. Employment Inducement Stock Option
                  Agreement, pursuant to which certain employees of Concept
                  Systems Holdings Limited (and its subsidiaries) were granted
                  inducement stock options to purchase shares of the
                  Registrant's common stock, which grants were made under the
                  Input/Output, Inc.- Concept Systems Employment Inducement
                  Stock Option Program.


                                      II-3
<PAGE>

         5.1      Opinion of Fulbright & Jaworski L.L.P.

         23.1     Consent of PricewaterhouseCoopers LLP.

         23.2     Consent of Deloitte & Touche LLP.

         23.3     Consent of Fulbright & Jaworski L.L.P. (included in the
                  opinion of Fulbright & Jaworski L.L.P. filed as Exhibit 5.1
                  hereto).

         24.1     Power of Attorney (included on the signature page hereto).

ITEM 9.   UNDERTAKINGS

         A. Undertaking to Update

         The undersigned Registrant hereby undertakes:

         (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, as amended (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 hereof) which, individually or in the aggregate,
represent a fundamental change in the information set forth in this Registration
Statement. Notwithstanding the foregoing, any increase or decrease in volume of
securities offered (if the total dollar value of securities offered would not
exceed that which was registered) and any deviation from the low or high end of
the estimated maximum offering range may be reflected in the form of prospectus
filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the
changes in volume and price represent no more than a 20 percent change in the
maximum aggregate offering price set forth in the "Calculation of Registration
Fee" table in this Registration Statement; and

                  (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 (i) and (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 Registrant pursuant to Section 13 or 15(d) of the Exchange Act
that are incorporated by reference in this Registration Statement.

         (2) That, for the purpose of determining any liability under the
Securities Act, 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.

         (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.


                                      II-4
<PAGE>

         B. Undertaking With Respect to Documents Incorporated by Reference

         The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or 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
herein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

         C. Undertaking With Respect to Indemnification

         Insofar as indemnification for liabilities arising under the Securities
Act 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 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 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 Securities Act and will be governed by the final
adjudication of such issue.


                                      II-5

<PAGE>


                                   SIGNATURES

         Pursuant to the requirements of the Securities Act, 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 Stafford, State of Texas, on July 23, 2004.


                                             INPUT/OUTPUT, INC.


                                             By:    /s/ Robert P. Peebler
                                                --------------------------------
                                                        Robert P. Peebler
                                                   President, Chief Executive
                                                      Officer and Director

                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each individual whose signature
appears below constitutes and appoints Robert P. Peebler and David L. Roland,
and each of them, his true and lawful attorneys-in-fact and agents, with full
power of substitution and resubstitution for him and in his name, place and
stead, in any and all capacities, to sign, execute and file this registration
statement under the Securities Act and any and all amendments (including,
without limitation, post-effective amendments and any amendment or amendments or
additional registration statement filed pursuant to Rule 462 under the
Securities Act increasing the amount of securities for which registration is
being sought) to this Registration Statement, and to file the same, with all
exhibits thereto, and any and all other documents in connection therewith, with
the Commission, to sign any and all applications, registration statements,
notices or other documents necessary or advisable to comply with the applicable
state securities laws, and to file the same, together with other documents in
connection therewith, with the appropriate state securities authorities,
granting unto said attorneys-in-fact and agents full power and authority to do
and perform each and every act and thing requisite and necessary to be done, as
fully to all intents and purposes as he might or could do in person, hereby
ratifying and confirming all that said attorneys-in-fact and agents or any of
them, or their or his substitute or substitutes, may lawfully do or cause to be
done by virtue hereof.

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

<Table>
<Caption>
                SIGNATURE                                       TITLE                                 DATE
                ---------                                       -----                                 ----
<S>                                            <C>                                               <C>
           /s/ Robert P. Peebler               President, Chief Executive Officer and            July 28, 2004
------------------------------------------                    Director
             Robert P. Peebler                      (principal executive officer)

          /s/ J. Michael Kirksey                      Executive Vice President                   July 28, 2004
------------------------------------------           and Chief Financial Officer
            J. Michael Kirksey                      (principal financial officer)

          /s/ Michael L. Morrison               Controller and Director of Accounting            July 28, 2004
------------------------------------------          (principal accounting officer)
            Michael L. Morrison
</TABLE>


                                      II-6
<PAGE>

<Table>
<Caption>
                SIGNATURE                                       TITLE                                 DATE
                ---------                                       -----                                 ----
<S>                                            <C>                                               <C>
         /s/ James M. Lapeyre, Jr.                    Chairman of the Board of                   July 28, 2004
------------------------------------------             Directors and Director
           James M. Lapeyre, Jr.

          /s/ Bruce S. Applebaum                              Director                           July 28, 2004
------------------------------------------
         Bruce S. Appelbaum, Ph.D

       /s/ Theodore H. Elliott, Jr.                           Director                           July 28, 2004
------------------------------------------
         Theodore H. Elliott, Jr.

            /s/ Franklin Myers                                Director                           July 28, 2004
------------------------------------------
              Franklin Myers

                                                              Director
------------------------------------------
               John N. Seitz

                                                              Director
------------------------------------------
               Sam K. Smith
</Table>


                                      II-7

<PAGE>


                                INDEX TO EXHIBITS


         4.1      Form of Input/Output, Inc. Employment Inducement Stock Option
                  Agreement, pursuant to which certain employees of Concept
                  Systems Holdings Limited (and its subsidiaries) were granted
                  inducement stock options to purchase shares of the
                  Registrant's common stock, which grants were made under the
                  Input/Output, Inc.- Concept Systems Employment Inducement
                  Stock Option Program.

         5.1      Opinion of Fulbright & Jaworski L.L.P.

         23.1     Consent of PricewaterhouseCoopers LLP.

         23.2     Consent of Deloitte & Touche LLP.

         23.3     Consent of Fulbright & Jaworski L.L.P. (included in the
                  opinion of Fulbright & Jaworski L.L.P. filed as Exhibit 5.1
                  hereto).

         24.1     Power of Attorney (included on the signature page hereto).
[{"type": "S-8", "sequence": "1", "filename": "h16813sv8.txt", "description": "INPUT/OUTPUT, INC.", "secsgml_size_bytes": 22048}]
{"company-data": {"conformed-name": "INPUT OUTPUT INC", "cik": "0000866609", "assigned-sic": "3829", "irs-number": "222286646", "state-of-incorporation": "DE", "fiscal-year-end": "0531"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-117716", "film-number": "04936224"}, "business-address": {"street1": "11104 W AIRPORT BLVD", "street2": "SUITE 200", "city": "STAFFORD", "state": "TX", "zip": "77477", "phone": "2819333339"}, "mail-address": {"street1": "11104 W AIRPORT BLVD", "street2": "SUITE 200", "city": "STAFFORD", "state": "TX", "zip": "77477"}}
REGISTRATION  NO. 333-

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

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

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

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

                               INPUT/OUTPUT, INC.
             (Exact name of registrant as specified in its charter)

            DELAWARE                                    22-2286646
  (State or other jurisdiction           (I.R.S. Employer Identification Number)
of incorporation or organization)

                              12300 PARC CREST DR.
                              STAFFORD, TEXAS 77477
                                 (281) 933-3339
    (Address, including zip code, and telephone number, including area code,
                  of registrant's principal executive offices)

  INPUT/OUTPUT, INC.- CONCEPT SYSTEMS EMPLOYMENT INDUCEMENT STOCK OPTION PROGRAM
                              (Full title of plan)

                              DAVID L. ROLAND, ESQ.
                         VICE PRESIDENT-GENERAL COUNSEL
                             AND CORPORATE SECRETARY
                               INPUT/OUTPUT, INC.
                              12300 PARC CREST DR.
                              STAFFORD, TEXAS 77477
                                 (281) 933-3339
            (Name, address and telephone number of agent for service)

                                 WITH COPIES TO:
                           FULBRIGHT & JAWORSKI L.L.P.
                            1301 MCKINNEY, SUITE 5100
                              HOUSTON, TEXAS 77010
                          ATTENTION: MARC H. FOLLADORI
                                 (713) 651-5151
CALCULATION OF REGISTRATION FEE
======================================================================================================================
                                                      PROPOSED           PROPOSED MAXIMUM
   TITLE OF SECURITIES        AMOUNT TO           MAXIMUM OFFERING      AGGREGATE OFFERING          AMOUNT OF
    TO BE REGISTERED       BE REGISTERED(2)      PRICE PER SHARE(2)          PRICE(2)            REGISTRATION FEE
----------------------------------------------------------------------------------------------------------------------
Common Stock
   $.01 par value(1)       365,000 shares              $8.32                $3,036,800                $384.76
======================================================================================================================
(1)  This Registration Statement also covers the associated rights to
        purchase Series A Preferred Stock, par value $0.01 per share, issued
        pursuant to that certain Rights Agreement dated as of January 17, 1997,
        by and between the registrant and Harris Trust and Savings Bank, as
        Rights Agent, as amended by the First Amendment
        to Rights Agreement, dated effective as of April 21, 1999.

   (2)  The 365,000 shares registered hereby represent shares issuable pursuant
        to the Input/Output, Inc.- Concept Systems Employment Inducement Stock
        Option Program, evidenced by stock option award agreements entered into
        between the registrant and the individual participants in such program.
        Pursuant to Rule 416(a), also registered hereunder is an indeterminate
        number of shares of common stock issuable as a result of certain
        anti-dilution provisions contained in those agreements. With respect to
        the shares registered hereby, the offering price per share, the
        aggregate offering price and the registration fee have been calculated
        in accordance with paragraphs (c) and (h)(1) of Rule 457 on the basis
        of the average high and low sale prices for the registrant's common
        stock on July 27, 2004 as reported on the New York Stock Exchange
        composite transactions ($8.32 per share).
INTRODUCTORY STATEMENT

         On February 23, 2004, Input/Output, Inc., a Delaware corporation ("I/O"
or the "Registrant") entered into a Share Acquisition Agreement with certain
security holders of Concept Systems Holding Limited, a private limited company
under the laws of Scotland ("Concept"), to acquire all of the share capital of
Concept.

         As contemplated by the terms of such acquisition agreement, the
Registrant granted certain employees of Concept (and its subsidiaries)
employment inducement stock option awards as a material inducement to their
joining the Registrant, under a program known as the Input/Output, Inc. -
Concept Systems Employment Inducement Stock Option Program.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE

         The contents of the following documents, filed by the Registrant with
the U.S. Securities and Exchange Commission (the "Commission"), are incorporated
into this registration statement (the "Registration Statement") by reference:

         o    The Registrant's Annual Report on Form 10-K for the fiscal year
              ended December 31, 2003, filed with the Commission on March 12,
              2004 pursuant to Section 13(a) of the Securities Exchange Act of
              1934, as amended (the "Exchange Act"), as amended by Form
              10-K/A-1 filed with the Commission on April 23, 2004 and as
              further amended by Form 10-K/A-2 filed with the Commission on May
              10, 2004;

         o    The Registrant's Quarterly Report on Form 10-Q for the fiscal
              quarter ended March 31, 2004, filed with the Commission on May 10,
              2004 pursuant to Section 13(a) of the Exchange Act;

         o    The Registrant's Current Reports on Form 8-K filed with the
              Commission on March 5, May 3 and May 11, 2004 (as amended by Form
              8-K/A-1 and Form 8-K/A-2 filed with the Commission on May 28,
              2004 and June 15, 2004, respectively), pursuant to Section 13(a)
              of the Exchange Act;

         o    The description of the Registrant's common stock contained in the
              Registration Statement on Form 8-A filed with the Commission on
              October 17, 1994, filed under Section 12(b) of the Exchange Act,
              as amended by the Registrant's Current Report on Form 8-K filed on
              March 8, 2002; and

         o    The Registrant's Registration Statement on Form 8-A12B filed with
              the Commission on January 27, 1997, as amended by Form 8-A12B/A
              filed on May 7, 1999.

         All documents filed by the Registrant with the Commission pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act subsequent to the filing
date of this Registration Statement and prior to the filing of a post-effective
amendment to this Registration Statement which indicates that all securities
offered have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated into this Registration Statement by
reference and to be a part hereof from the date of filing of each such document.

                                      II-2
ITEM 4.  DESCRIPTION OF SECURITIES

         Not applicable.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL

         Not applicable.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         The General Corporation Law of the State of Delaware ("DGCL") permits
the Registrant and its stockholders to limit directors' exposure to liability
for certain breaches of the directors' fiduciary duty. The Restated Certificate
of Incorporation of the Registrant, as amended (the "Charter"), provides that a
director of the Registrant shall not be personally liable to the Registrant or
its stockholders for monetary damages for breach of fiduciary duty as a
director, except for liability (i) for any breach of the director's duty of
loyalty to the Registrant or its stockholders, (ii) for acts or omissions not in
good faith or which involve intentional misconduct or a knowing violation of
law, (iii) under Section 174 of the DGCL or (iv) for any transaction from which
the director derived an improper personal benefit.

         The Amended and Restated Bylaws of the Registrant (the "Bylaws")
provide that the Registrant shall, to the full extent permitted by applicable
laws (including the DGCL), indemnify its directors, officers, employees and
agents with respect to expenses (including counsel fees), judgments, fines,
penalties and other liabilities and amounts incurred by any such person in
connection with any threatened, pending or completed action, suit or proceeding
to which such person is or was a party, or is or was threatened to be made a
party, by reason of the fact that such person is or was serving as a director,
officer, employee or agent of the Registrant or any of its direct or indirect
wholly owned subsidiaries, or is or was serving at the request of the Registrant
or any of its direct or indirect wholly owned subsidiaries as a director,
officer, employee, agent or trustee of another corporation, partnership, joint
venture, trust, employee benefit plan or other enterprise. The Bylaws provide
that the indemnification provided pursuant to the Bylaws is not exclusive of any
other rights to which those seeking indemnification may be entitled under any
provision of law, certificate of incorporation, bylaws, governing documents,
agreement, vote of stockholders or disinterested directors of the Registrant or
any of its direct or indirect wholly owned subsidiaries, or otherwise.

         The Registrant maintains a standard form of officers' and directors'
liability insurance policy which provides coverage to the officers and directors
of the Registrant for certain liabilities, including certain liabilities which
may arise out of this Registration Statement.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Not applicable.

ITEM 8.  EXHIBITS

         4.1      Form of Input/Output, Inc. Employment Inducement Stock Option
                  Agreement, pursuant to which certain employees of Concept
                  Systems Holdings Limited (and its subsidiaries) were granted
                  inducement stock options to purchase shares of the
                  Registrant's common stock, which grants were made under the
                  Input/Output, Inc.- Concept Systems Employment Inducement
                  Stock Option Program.

                                      II-3
5.1      Opinion of Fulbright & Jaworski L.L.P.

         23.1     Consent of PricewaterhouseCoopers LLP.

         23.2     Consent of Deloitte & Touche LLP.

         23.3     Consent of Fulbright & Jaworski L.L.P. (included in the
                  opinion of Fulbright & Jaworski L.L.P. filed as Exhibit 5.1
                  hereto).

         24.1     Power of Attorney (included on the signature page hereto).

ITEM 9.   UNDERTAKINGS

         A. Undertaking to Update

         The undersigned Registrant hereby undertakes:

         (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, as amended (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 hereof) which, individually or in the aggregate,
represent a fundamental change in the information set forth in this Registration
Statement. Notwithstanding the foregoing, any increase or decrease in volume of
securities offered (if the total dollar value of securities offered would not
exceed that which was registered) and any deviation from the low or high end of
the estimated maximum offering range may be reflected in the form of prospectus
filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the
changes in volume and price represent no more than a 20 percent change in the
maximum aggregate offering price set forth in the "Calculation of Registration
Fee" table in this Registration Statement; and

                  (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 (i) and (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 Registrant pursuant to Section 13 or 15(d) of the Exchange Act
that are incorporated by reference in this Registration Statement.

         (2) That, for the purpose of determining any liability under the
Securities Act, 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.

         (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.

                                      II-4
B. Undertaking With Respect to Documents Incorporated by Reference

         The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or 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
herein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

         C. Undertaking With Respect to Indemnification

         Insofar as indemnification for liabilities arising under the Securities
Act 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 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 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 Securities Act and will be governed by the final
adjudication of such issue.

                                      II-5
SIGNATURES

         Pursuant to the requirements of the Securities Act, 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 Stafford, State of Texas, on July 23, 2004.

                                             INPUT/OUTPUT, INC.

                                             By:    /s/ Robert P. Peebler
                                                --------------------------------
                                                        Robert P. Peebler
                                                   President, Chief Executive
                                                      Officer and Director

                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each individual whose signature
appears below constitutes and appoints Robert P. Peebler and David L. Roland,
and each of them, his true and lawful attorneys-in-fact and agents, with full
power of substitution and resubstitution for him and in his name, place and
stead, in any and all capacities, to sign, execute and file this registration
statement under the Securities Act and any and all amendments (including,
without limitation, post-effective amendments and any amendment or amendments or
additional registration statement filed pursuant to Rule 462 under the
Securities Act increasing the amount of securities for which registration is
being sought) to this Registration Statement, and to file the same, with all
exhibits thereto, and any and all other documents in connection therewith, with
the Commission, to sign any and all applications, registration statements,
notices or other documents necessary or advisable to comply with the applicable
state securities laws, and to file the same, together with other documents in
connection therewith, with the appropriate state securities authorities,
granting unto said attorneys-in-fact and agents full power and authority to do
and perform each and every act and thing requisite and necessary to be done, as
fully to all intents and purposes as he might or could do in person, hereby
ratifying and confirming all that said attorneys-in-fact and agents or any of
them, or their or his substitute or substitutes, may lawfully do or cause to be
done by virtue hereof.

         Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed by the following persons in the capacities and on the
dates indicated.
SIGNATURE                                       TITLE                                 DATE
                ---------                                       -----                                 ----
/s/ Robert P. Peebler               President, Chief Executive Officer and            July 28, 2004
------------------------------------------                    Director
             Robert P. Peebler                      (principal executive officer)

          /s/ J. Michael Kirksey                      Executive Vice President                   July 28, 2004
------------------------------------------           and Chief Financial Officer
            J. Michael Kirksey                      (principal financial officer)

          /s/ Michael L. Morrison               Controller and Director of Accounting            July 28, 2004
------------------------------------------          (principal accounting officer)
            Michael L. Morrison
II-6
SIGNATURE                                       TITLE                                 DATE
                ---------                                       -----                                 ----
/s/ James M. Lapeyre, Jr.                    Chairman of the Board of                   July 28, 2004
------------------------------------------             Directors and Director
           James M. Lapeyre, Jr.

          /s/ Bruce S. Applebaum                              Director                           July 28, 2004
------------------------------------------
         Bruce S. Appelbaum, Ph.D

       /s/ Theodore H. Elliott, Jr.                           Director                           July 28, 2004
------------------------------------------
         Theodore H. Elliott, Jr.

            /s/ Franklin Myers                                Director                           July 28, 2004
------------------------------------------
              Franklin Myers

                                                              Director
------------------------------------------
               John N. Seitz

                                                              Director
------------------------------------------
               Sam K. Smith
II-7
INDEX TO EXHIBITS

         4.1      Form of Input/Output, Inc. Employment Inducement Stock Option
                  Agreement, pursuant to which certain employees of Concept
                  Systems Holdings Limited (and its subsidiaries) were granted
                  inducement stock options to purchase shares of the
                  Registrant's common stock, which grants were made under the
                  Input/Output, Inc.- Concept Systems Employment Inducement
                  Stock Option Program.

         5.1      Opinion of Fulbright & Jaworski L.L.P.

         23.1     Consent of PricewaterhouseCoopers LLP.

         23.2     Consent of Deloitte & Touche LLP.

         23.3     Consent of Fulbright & Jaworski L.L.P. (included in the
                  opinion of Fulbright & Jaworski L.L.P. filed as Exhibit 5.1
                  hereto).

         24.1     Power of Attorney (included on the signature page hereto).