EXHIBIT 23.1 CONSENT OF INDEPENDENT AUDITORS We consent to the incorporation by reference in the Registration Statement (Form S-8) and related Prospectuses pertaining to the Employee Stock Purchase Plan of Arthur J. Gallagher & Co. of our report dated January 29, 2003 with respect to the consolidated financial statements of Arthur J. Gallagher & Co. and subsidiaries included in its Current Report on Form 8-K dated June 25, 2003 filed with the Securities and Exchange Commission and of our report dated January 29, 2003 with respect to the schedule of Arthur J. Gallagher & Co. and subsidiaries included in its Annual Report on Form 10-K for the year ended December 31, 2002 filed with the Securities and Exchange Commission. /s/ Ernst & Young LLP ---------------------- Ernst & Young LLP Chicago, Illinois June 26, 2003