EXHIBIT NUMBER (23) TO 1999 FORM 10-K CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS As independent public accountants, we hereby consent to the incorporation of our report dated January 18, 2000, incorporated by reference in the Northern Trust Corporation's Annual Report on Form 10-K for the year end December 31, 1999, into the Corporation's previously filed Form S-8 Registration Statements File Nos. 33-22546, 33-47597, 33-63843, 333-25283, 333-52623, 333-53259, 333- 74951, 333-84085; and the Corporation's previously filed Form S-3 Nos. 333-18951 and 333-25649. /s/ ARTHUR ANDERSEN LLP --------------------------------- ARTHUR ANDERSEN LLP Chicago, Illinois March 14, 2000