<PAGE>
 
     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 18, 1998
 
                                                     REGISTRATION NO.
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
 
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549
 
                               ----------------
 
                                   FORM S-8
                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933
 
                               ----------------
 
                           ARTHUR J. GALLAGHER & CO.
            (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
 
                               ----------------
 
               DELAWARE                              36-2151613
       (STATE OF INCORPORATION)         (I.R.S. EMPLOYER IDENTIFICATION NO.)
 
                               TWO PIERCE PLACE
                          ITASCA, ILLINOIS 60143-3141
                   (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
 
                               ----------------
 
                           ARTHUR J. GALLAGHER & CO.
                       1988 INCENTIVE STOCK OPTION PLAN
                           ARTHUR J. GALLAGHER & CO.
                      1988 NONQUALIFIED STOCK OPTION PLAN
                           (FULL TITLE OF THE PLAN)
 
                               ----------------
 
                                 CARL E. FASIG
                        CORPORATE COUNSEL AND SECRETARY
                           ARTHUR J. GALLAGHER & CO.
                               TWO PIERCE PLACE
                          ITASCA, ILLINOIS 60143-3141
                                (630) 285-3449
           (NAME, ADDRESS AND TELEPHONE NUMBER OF AGENT FOR SERVICE)
 
                        CALCULATION OF REGISTRATION FEE
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
<TABLE>
<CAPTION>
                                                    PROPOSED       PROPOSED
                                      AMOUNT        MAXIMUM        MAXIMUM       AMOUNT OF
    TITLE OF SECURITIES TO BE         TO BE      OFFERING PRICE   AGGREGATE     REGISTRATION
           REGISTERED               REGISTERED     PER SHARE    OFFERING PRICE      FEE
--------------------------------------------------------------------------------------------
<S>                               <C>            <C>            <C>            <C>
Common Stock, par value
 $1.00 per share.................   500,000(a)     $42.75(b)     $21,375,000     $6,306.00
--------------------------------------------------------------------------------------------
</TABLE>
-------------------------------------------------------------------------------
(a) Includes such indeterminant number of shares as may be issuable by reason
    of the operation of the anti-dilution provisions of the Plans.
(b) Estimated in accordance with Rule 457(c) solely for the purpose of
    computing the registration fee on the basis of the average of the high and
    low prices quoted for the Registrant's Common Stock, as reported on the
    consolidated transaction reporting system for securities listed on the New
    York Stock Exchange on June 16, 1998.
 
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
<PAGE>
 
                                    PART II
 
              INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
 
ITEM 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.
 
  The following documents are incorporated by reference in the registration
statement:
 
  The Post-Effective Amendment No. 1 to the Company's Registration Statement
on Form S-1 (Registration No. 333-23897) declared effective by the Commission
on March 27, 1998, the Company's annual report on Form 10-K for the year ended
December 31, 1997, and the Company's quarterly report on Form 10-Q for the
quarter ended March 31, 1998, are incorporated herein by reference. Also
incorporated herein by reference is the description of the Common Stock
registered hereunder contained in Form 8-A (Registration No. 0-13480), which
incorporates by reference the Company's Registration Statement on Form S-1
(Registration No. 2-89195) and the description of common share purchase rights
currently attached to the Common Stock contained in Form 8-A (Registration No.
0-13480) filed with the Commission on May 12, 1987, and in the Company's
Current Report on Form 8-K (Registration No. 0-13480) filed with the
Commission on May 18, 1987.
 
  All documents subsequently filed by the registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, prior to
the filing of a post-effective amendment to the registration statement which
indicates that all of the shares of common stock offered have been sold or
which deregisters all of such shares then remaining unsold, shall be deemed to
be incorporated by reference in the registration statement and to be a part
hereof from the date of filing of 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 which also is or is deemed to be incorporated by
reference herein modifies or supersedes such statement. Any such statement so
modified or superseded shall not be deemed, except as so modified or
superseded, to constitute a part of this registration statement.
 
ITEM 4. DESCRIPTION OF SECURITIES.
 
  Not applicable.
 
ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.
 
  The legality of the shares of Common Stock offered under these Plans will be
passed upon by Carl E. Fasig, Corporate Counsel and Secretary for the Company.
Mr. Fasig holds options with respect to 4,100 shares of Common Stock that are
exercisable more than 60 days from the date of this Registration Statement.
 
ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
  Article Seventh of the Registrant's By-laws (filed as Exhibit 3.2) and
Article Thirteenth of the Company's Restated Certificate of Incorporation
(filed as Exhibit 3.1) provide in effect for the indemnification by the
Registrant of each director, officer, employee or agent of the Registrant to
the full extent permitted by the Delaware General Corporation Law.
 
  Article Seventh of the Registrant's By-laws provides that the Registrant
shall indemnify any person in connection with any action, suit, or proceeding
brought or threatened by reason of the fact that he is or was a director,
officer, employee or agent of the Registrant, or is or was serving at the
request of the Registrant as a director, officer, employee or agent of another
enterprise against all costs actually and reasonably incurred by him in
connection with such action, suit or proceeding 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 Registrant, and, with respect to any criminal action or
proceeding, had no reasonable cause to believe his conduct was unlawful.
Similar indemnity is permitted to be provided to such persons in connection
with an action or suit by or in the right of the Registrant, and
 
                                       1
<PAGE>
 
provided further that such person shall not have been adjudged liable for
negligence or misconduct in the performance of his duty to the Registrant,
unless, in view of all the circumstances of the case, the court in which the
action or suit was brought determines that such person despite the
adjudication of liability is fairly and reasonably entitled to indemnity for
such expenses.
 
  Article Thirteenth of the Company's Restated Certificate of Incorporation
eliminates the liability of the Company's directors for monetary damages for
breach of fiduciary duty as a director except where a director breaches his
duty of loyalty to the Company and its stockholders, fails to act in good
faith or engages in intentional misconduct or a knowing violation of law,
authorizes the payment of a dividend or stock repurchase which is illegal
under Section 174 of the Delaware General Corporation Laws or obtains an
improper personal benefit.
 
  The Registrant also maintains and pays premiums on a directors' and
officers' liability insurance policy and entered into an Indemnity Agreement
with each of the directors and officers of the Company. The provisions of the
Indemnity Agreement alter or clarify the statutory indemnity in the following
respects: (1) indemnity will be explicitly provided for settlements in
derivative actions; (2) prompt payment of litigation expenses will be provided
in advance of indemnification; (3) prompt indemnification of advances of
expenses will be provided unless a determination is made that the director or
officer has not met the required standard; (4) the director or officer will be
permitted to petition a court to determine whether his actions meet the
standards required; and (5) partial indemnification will be permitted in the
event that the director or officer is not entitled to full indemnification. In
addition, the Indemnity Agreement specifically includes indemnification with
respect to actions, suits or proceedings brought under and/or predicated upon
the Securities Act of 1933, as amended, and/or the Securities Exchange Act of
1934, as amended.
 
  The preceding summary is qualified in its entirety by the Company's Restated
Certificate of Incorporation, By-laws and Indemnity Agreement which are filed
as exhibits to this Registration Statement and for further information,
reference is made thereto.
 
ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.
 
  Not applicable.
 
ITEM 8. EXHIBITS.
 
  The exhibits to the registration statement are listed in the Exhibit Index
elsewhere herein.
 
ITEM 9. UNDERTAKINGS.
 
  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;
 
      (ii) To reflect in the prospectus any facts or events arising after
    the effective date of the Registration Statement (or the most recent
    post-effective amendment thereof) which, individually or in the
    aggregate, represent a fundamental change in the information set forth
    in the Registration Statement; and
 
      (iii) To include any material information with respect to the plan of
    distribution not previously disclosed in the Registration Statement or
    any material change to such information in the Registration Statement,
    including (but not limited to) any addition or deletion of a managing
    underwriter.
 
                                       2
<PAGE>
 
    (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.
 
    (3) 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 (and,
  where applicable, each filing of an employee benefit plan's annual report
  pursuant to section 15(d) of the Securities Exchange Act of 1934) that is
  incorporated by reference in the 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.
 
    (4) 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.
 
    (5) 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 any provision of the
  Registrant's By-laws, Directors' and Officers' Liability Insurance Policy,
  or otherwise, the Registrant has been advised that in the opinion of the
  Securities and Exchange Commission such 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.
 
SAFE HARBOR STATEMENT UNDER THE PRIVATE SECURITIES LITIGATION REFORM ACT OF
1995
 
  This Registration Statement contains forward-looking statements. Forward-
looking statements made by or on behalf of the Company are subject to risks
and uncertainties, including but not limited to the following: the Company's
commission revenues are highly dependent on premiums charged by insurers,
which are subject to fluctuation; the property/casualty insurance industry
continues to experience a prolonged soft market, despite high losses which
reduces premiums thereby reducing commissions; continued low interest rates
will reduce the Company's income earned on invested funds; the insurance
brokerage and service businesses are extremely competitive with a number of
competitors being substantially larger than the Company; the alternative
insurance market continues to grow which could unfavorably impact commission
and favorably impact fee revenue; the Company's revenues vary significantly
from quarter to quarter as a result of the timing of policy renewals and the
net effect of new and lost business production; the general level of economic
activity can have a substantial impact on the Company's renewal business. The
Company's ability to grow has been enhanced through acquisitions, which may or
may not be available on acceptable terms in the future, and which, if
consummated, may or may not be advantageous to the Company. Accordingly,
actual results may differ materially from those set forth in the forward
looking statements. Attention is also directed to other risk factors set forth
in documents filed by the Company with the Securities and Exchange Commission.
 
                                       3
<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 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 ITASCA AND STATE OF ILLINOIS, ON THE 18TH DAY OF
JUNE, 1998.
 
                                          Arthur J. Gallagher & Co.
 
                                               /s/ J. Patrick Gallagher, Jr.
                                          By: _________________________________
                                                 J. Patrick Gallagher, Jr.
                                               President and Chief Executive
                                                          Officer
 
  PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THIS
REGISTRATION STATEMENT ON FORM S-8 HAS BEEN SIGNED BY THE FOLLOWING PERSONS IN
THE CAPACITIES INDICATED ON JUNE 18, 1998.
 
<TABLE>
<CAPTION>
                 SIGNATURE                                     TITLE
                 ---------                                     -----
<S>                                         <C>
           Robert E. Gallagher*
-------------------------------------------
            Robert E. Gallagher             Chairman and Director
       /s/ J. Patrick Gallagher, Jr.
-------------------------------------------
         J. Patrick Gallagher, Jr.          President and Director (Chief Executive
                                             Officer)
          /s/ Michael J. Cloherty
-------------------------------------------
            Michael J. Cloherty             Executive Vice President and Director
                                             (Chief Financial Officer)
            /s/ Jack H. Lazzaro
-------------------------------------------
              Jack H. Lazzaro               Vice President--Finance (Chief Accounting
                                             Officer)
            T. Kimball Brooker*
-------------------------------------------
            T. Kimball Brooker              Director
             Jack M. Greenberg*
-------------------------------------------
             Jack M. Greenberg              Director
          Frank M. Heffernan, Jr.*
-------------------------------------------
          Frank M. Heffernan, Jr.           Director
            Philip A. Marineau*
-------------------------------------------
            Philip A. Marineau              Director
             Walter F. McClure*
-------------------------------------------
             Walter F. McClure              Director
              James R. Wimmer*
-------------------------------------------
              James R. Wimmer               Director
</TABLE>
 
          /s/ Carl E. Fasig
*By: ________________________________
            Carl E. Fasig,
           Attorney-in-Fact
 
                                       4
<PAGE>
 
                               INDEX TO EXHIBITS
 
<TABLE>
<CAPTION>
  EXHIBIT
  NUMBER                                EXHIBIT
  -------                               -------
 <C>       <S>
   *5.0    Consent of Carl E. Fasig, Corporate Counsel and Secretary to the
           Company.
  *23.1    Consent of Ernst & Young LLP, as independent auditors.
  *23.2    Consent of Carl E. Fasig, Corporate Counsel and Secretary to the
           Company, included in Exhibit 5.0.
  *24.0    Powers of Attorney.
</TABLE>
 
  All other exhibits and schedules are omitted because they are not applicable
or not required or because the required information is included in the
Consolidated Financial Statements or Notes thereto.
 
--------
 *Filed herewith.
 
                                       5
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 19209}]
{"company-data": {"conformed-name": "GALLAGHER ARTHUR J & CO", "cik": "0000354190", "assigned-sic": "6411", "irs-number": "362151613", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-57155", "film-number": "98650348"}, "business-address": {"street1": "TWO PIERCE PL", "city": "ITASCA", "state": "IL", "zip": "60143", "phone": "7087733800"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 18, 1998
 
                                                     REGISTRATION NO.
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
 
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549
 
                               ----------------
 
                                   FORM S-8
                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933
 
                               ----------------
 
                           ARTHUR J. GALLAGHER & CO.
            (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
 
                               ----------------
 
               DELAWARE                              36-2151613
       (STATE OF INCORPORATION)         (I.R.S. EMPLOYER IDENTIFICATION NO.)
 
                               TWO PIERCE PLACE
                          ITASCA, ILLINOIS 60143-3141
                   (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
 
                               ----------------
 
                           ARTHUR J. GALLAGHER & CO.
                       1988 INCENTIVE STOCK OPTION PLAN
                           ARTHUR J. GALLAGHER & CO.
                      1988 NONQUALIFIED STOCK OPTION PLAN
                           (FULL TITLE OF THE PLAN)
 
                               ----------------
 
                                 CARL E. FASIG
                        CORPORATE COUNSEL AND SECRETARY
                           ARTHUR J. GALLAGHER & CO.
                               TWO PIERCE PLACE
                          ITASCA, ILLINOIS 60143-3141
                                (630) 285-3449
           (NAME, ADDRESS AND TELEPHONE NUMBER OF AGENT FOR SERVICE)
 
                        CALCULATION OF REGISTRATION FEE
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
PROPOSED       PROPOSED
                                      AMOUNT        MAXIMUM        MAXIMUM       AMOUNT OF
    TITLE OF SECURITIES TO BE         TO BE      OFFERING PRICE   AGGREGATE     REGISTRATION
           REGISTERED               REGISTERED     PER SHARE    OFFERING PRICE      FEE
--------------------------------------------------------------------------------------------
Common Stock, par value
 $1.00 per share.................   500,000(a)     $42.75(b)     $21,375,000     $6,306.00
--------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------
(a) Includes such indeterminant number of shares as may be issuable by reason
    of the operation of the anti-dilution provisions of the Plans.
(b) Estimated in accordance with Rule 457(c) solely for the purpose of
    computing the registration fee on the basis of the average of the high and
    low prices quoted for the Registrant's Common Stock, as reported on the
    consolidated transaction reporting system for securities listed on the New
    York Stock Exchange on June 16, 1998.
 
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
PART II
 
              INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
 
ITEM 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.
 
  The following documents are incorporated by reference in the registration
statement:
 
  The Post-Effective Amendment No. 1 to the Company's Registration Statement
on Form S-1 (Registration No. 333-23897) declared effective by the Commission
on March 27, 1998, the Company's annual report on Form 10-K for the year ended
December 31, 1997, and the Company's quarterly report on Form 10-Q for the
quarter ended March 31, 1998, are incorporated herein by reference. Also
incorporated herein by reference is the description of the Common Stock
registered hereunder contained in Form 8-A (Registration No. 0-13480), which
incorporates by reference the Company's Registration Statement on Form S-1
(Registration No. 2-89195) and the description of common share purchase rights
currently attached to the Common Stock contained in Form 8-A (Registration No.
0-13480) filed with the Commission on May 12, 1987, and in the Company's
Current Report on Form 8-K (Registration No. 0-13480) filed with the
Commission on May 18, 1987.
 
  All documents subsequently filed by the registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, prior to
the filing of a post-effective amendment to the registration statement which
indicates that all of the shares of common stock offered have been sold or
which deregisters all of such shares then remaining unsold, shall be deemed to
be incorporated by reference in the registration statement and to be a part
hereof from the date of filing of 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 which also is or is deemed to be incorporated by
reference herein modifies or supersedes such statement. Any such statement so
modified or superseded shall not be deemed, except as so modified or
superseded, to constitute a part of this registration statement.
 
ITEM 4. DESCRIPTION OF SECURITIES.
 
  Not applicable.
 
ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.
 
  The legality of the shares of Common Stock offered under these Plans will be
passed upon by Carl E. Fasig, Corporate Counsel and Secretary for the Company.
Mr. Fasig holds options with respect to 4,100 shares of Common Stock that are
exercisable more than 60 days from the date of this Registration Statement.
 
ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
  Article Seventh of the Registrant's By-laws (filed as Exhibit 3.2) and
Article Thirteenth of the Company's Restated Certificate of Incorporation
(filed as Exhibit 3.1) provide in effect for the indemnification by the
Registrant of each director, officer, employee or agent of the Registrant to
the full extent permitted by the Delaware General Corporation Law.
 
  Article Seventh of the Registrant's By-laws provides that the Registrant
shall indemnify any person in connection with any action, suit, or proceeding
brought or threatened by reason of the fact that he is or was a director,
officer, employee or agent of the Registrant, or is or was serving at the
request of the Registrant as a director, officer, employee or agent of another
enterprise against all costs actually and reasonably incurred by him in
connection with such action, suit or proceeding 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 Registrant, and, with respect to any criminal action or
proceeding, had no reasonable cause to believe his conduct was unlawful.
Similar indemnity is permitted to be provided to such persons in connection
with an action or suit by or in the right of the Registrant, and
 
                                       1
provided further that such person shall not have been adjudged liable for
negligence or misconduct in the performance of his duty to the Registrant,
unless, in view of all the circumstances of the case, the court in which the
action or suit was brought determines that such person despite the
adjudication of liability is fairly and reasonably entitled to indemnity for
such expenses.
 
  Article Thirteenth of the Company's Restated Certificate of Incorporation
eliminates the liability of the Company's directors for monetary damages for
breach of fiduciary duty as a director except where a director breaches his
duty of loyalty to the Company and its stockholders, fails to act in good
faith or engages in intentional misconduct or a knowing violation of law,
authorizes the payment of a dividend or stock repurchase which is illegal
under Section 174 of the Delaware General Corporation Laws or obtains an
improper personal benefit.
 
  The Registrant also maintains and pays premiums on a directors' and
officers' liability insurance policy and entered into an Indemnity Agreement
with each of the directors and officers of the Company. The provisions of the
Indemnity Agreement alter or clarify the statutory indemnity in the following
respects: (1) indemnity will be explicitly provided for settlements in
derivative actions; (2) prompt payment of litigation expenses will be provided
in advance of indemnification; (3) prompt indemnification of advances of
expenses will be provided unless a determination is made that the director or
officer has not met the required standard; (4) the director or officer will be
permitted to petition a court to determine whether his actions meet the
standards required; and (5) partial indemnification will be permitted in the
event that the director or officer is not entitled to full indemnification. In
addition, the Indemnity Agreement specifically includes indemnification with
respect to actions, suits or proceedings brought under and/or predicated upon
the Securities Act of 1933, as amended, and/or the Securities Exchange Act of
1934, as amended.
 
  The preceding summary is qualified in its entirety by the Company's Restated
Certificate of Incorporation, By-laws and Indemnity Agreement which are filed
as exhibits to this Registration Statement and for further information,
reference is made thereto.
 
ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.
 
  Not applicable.
 
ITEM 8. EXHIBITS.
 
  The exhibits to the registration statement are listed in the Exhibit Index
elsewhere herein.
 
ITEM 9. UNDERTAKINGS.
 
  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;
 
      (ii) To reflect in the prospectus any facts or events arising after
    the effective date of the Registration Statement (or the most recent
    post-effective amendment thereof) which, individually or in the
    aggregate, represent a fundamental change in the information set forth
    in the Registration Statement; and
 
      (iii) To include any material information with respect to the plan of
    distribution not previously disclosed in the Registration Statement or
    any material change to such information in the Registration Statement,
    including (but not limited to) any addition or deletion of a managing
    underwriter.
 
                                       2
(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.
 
    (3) 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 (and,
  where applicable, each filing of an employee benefit plan's annual report
  pursuant to section 15(d) of the Securities Exchange Act of 1934) that is
  incorporated by reference in the 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.
 
    (4) 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.
 
    (5) 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 any provision of the
  Registrant's By-laws, Directors' and Officers' Liability Insurance Policy,
  or otherwise, the Registrant has been advised that in the opinion of the
  Securities and Exchange Commission such 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.
 
SAFE HARBOR STATEMENT UNDER THE PRIVATE SECURITIES LITIGATION REFORM ACT OF
1995
 
  This Registration Statement contains forward-looking statements. Forward-
looking statements made by or on behalf of the Company are subject to risks
and uncertainties, including but not limited to the following: the Company's
commission revenues are highly dependent on premiums charged by insurers,
which are subject to fluctuation; the property/casualty insurance industry
continues to experience a prolonged soft market, despite high losses which
reduces premiums thereby reducing commissions; continued low interest rates
will reduce the Company's income earned on invested funds; the insurance
brokerage and service businesses are extremely competitive with a number of
competitors being substantially larger than the Company; the alternative
insurance market continues to grow which could unfavorably impact commission
and favorably impact fee revenue; the Company's revenues vary significantly
from quarter to quarter as a result of the timing of policy renewals and the
net effect of new and lost business production; the general level of economic
activity can have a substantial impact on the Company's renewal business. The
Company's ability to grow has been enhanced through acquisitions, which may or
may not be available on acceptable terms in the future, and which, if
consummated, may or may not be advantageous to the Company. Accordingly,
actual results may differ materially from those set forth in the forward
looking statements. Attention is also directed to other risk factors set forth
in documents filed by the Company with the Securities and Exchange Commission.
 
                                       3
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 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 ITASCA AND STATE OF ILLINOIS, ON THE 18TH DAY OF
JUNE, 1998.
 
                                          Arthur J. Gallagher & Co.
 
                                               /s/ J. Patrick Gallagher, Jr.
                                          By: _________________________________
                                                 J. Patrick Gallagher, Jr.
                                               President and Chief Executive
                                                          Officer
 
  PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THIS
REGISTRATION STATEMENT ON FORM S-8 HAS BEEN SIGNED BY THE FOLLOWING PERSONS IN
THE CAPACITIES INDICATED ON JUNE 18, 1998.
SIGNATURE                                     TITLE
                 ---------                                     -----
Robert E. Gallagher*
-------------------------------------------
            Robert E. Gallagher             Chairman and Director
       /s/ J. Patrick Gallagher, Jr.
-------------------------------------------
         J. Patrick Gallagher, Jr.          President and Director (Chief Executive
                                             Officer)
          /s/ Michael J. Cloherty
-------------------------------------------
            Michael J. Cloherty             Executive Vice President and Director
                                             (Chief Financial Officer)
            /s/ Jack H. Lazzaro
-------------------------------------------
              Jack H. Lazzaro               Vice President--Finance (Chief Accounting
                                             Officer)
            T. Kimball Brooker*
-------------------------------------------
            T. Kimball Brooker              Director
             Jack M. Greenberg*
-------------------------------------------
             Jack M. Greenberg              Director
          Frank M. Heffernan, Jr.*
-------------------------------------------
          Frank M. Heffernan, Jr.           Director
            Philip A. Marineau*
-------------------------------------------
            Philip A. Marineau              Director
             Walter F. McClure*
-------------------------------------------
             Walter F. McClure              Director
              James R. Wimmer*
-------------------------------------------
              James R. Wimmer               Director
/s/ Carl E. Fasig
*By: ________________________________
            Carl E. Fasig,
           Attorney-in-Fact
 
                                       4
INDEX TO EXHIBITS
EXHIBIT
  NUMBER                                EXHIBIT
  -------                               -------
*5.0    Consent of Carl E. Fasig, Corporate Counsel and Secretary to the
           Company.
  *23.1    Consent of Ernst & Young LLP, as independent auditors.
  *23.2    Consent of Carl E. Fasig, Corporate Counsel and Secretary to the
           Company, included in Exhibit 5.0.
  *24.0    Powers of Attorney.
All other exhibits and schedules are omitted because they are not applicable
or not required or because the required information is included in the
Consolidated Financial Statements or Notes thereto.
 
--------
 *Filed herewith.
 
                                       5