Exhibit 32.2 Certificate Pursuant to Section 1350 of Chapter 63 of Title 18 of the United States Code I, Douglas K. Howell, the chief financial officer of Arthur J. Gallagher & Co., certify that (i) the Quarterly Report on Form 10-Q of Arthur J. Gallagher & Co. for the quarterly period ended June 30, 2003 (the "Form 10-Q") fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and (ii) the information contained in the Form 10-Q fairly presents, in all material respects, the financial condition and results of operations of Arthur J. Gallagher & Co. and its subsidiaries. Date: July 24, 2003 /s/ Douglas K. Howell ----------------------------- Douglas K. Howell Vice President Chief Financial Officer (principal financial officer) A signed original of this written statement required by Section 906 has been provided to Arthur J. Gallagher & Co. and will be retained by Arthur J. Gallagher & Co. and furnished to the Securities and Exchange Commission or its staff upon request.