EXHIBIT 5.0


                           ARTHUR J. GALLAGHER & CO.

                                                                   June 23, 2000

Securities and Exchange Commission
450 Fifth Street N.W.
Washington, D.C. 20549

Re: Arthur J. Gallagher & Co.
  Registration Statement on Form S-8

Gentlemen:

   I am counsel for Arthur J. Gallagher & Co. (the "Company") in connection
with the above referenced Registration Statement on Form S-8 (the "Registration
Statement"), relating to the registration of 1,070,000 shares of the Company's
Common Stock, par value $1.00 per share (the "Shares"), to be issued pursuant
to the terms of the Arthur J. Gallagher & Co. 1988 Nonqualified Stock Option
Plan and 1989 Non-Employee Directors' Stock Option Plan (the "Plans").

   In this connection, I have examined the originals or copies identified to my
satisfaction of such documents, corporate and other records, certificates, and
other papers as I deemed necessary to examine for purposes of this opinion.

   Based upon such examination, I am of the opinion that the Shares of Common
Stock which may be issued to officers, employees and directors of the Company
pursuant to the Plans will be duly and legally authorized and issued, fully
paid, and non-assessable.

   I hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to me in the Registration Statement
and the related Prospectuses.

                                          Very truly yours,

                                          JOHN C. ROSENGREN
                                          Vice President and General Counsel