Exhibit 5 April 15, 1997 Securities and Exchange Commission Judiciary Plaza 450 Fifth Street, N.W. Washington, DC 20549-1004 Re: Northern Trust Corporation - Registration Statement on Form S-8 Ladies and Gentlemen: I am Executive Vice President, General Counsel and Secretary of Northern Trust Corporation, a Delaware corporation (the "Corporation"), and have served in that capacity in connection with the Corporation s filing of a Registration Statement on Form S-8 (the "Registration Statement") with the Securities and Exchange Commission covering the registration of an additional 8,500,000 shares of the Corporation s common stock, $1.66 2/3 par value per share, including the associated Preferred Stock Purchase Rights (collectively, the "Stock"), issuable pursuant to the Northern Trust Corporation Amended 1992 Incentive Stock Plan (the "Plan"). In that connection, I have examined such documents and have made such factual and legal investigations as I have deemed necessary or appropriate for the purpose of this opinion. Based upon the foregoing, it is my opinion that those shares of Stock covered by the Registration Statement that are issued in accordance with the terms of the Plan will be legally issued, fully paid and non-assessable. I hereby consent to the filing of this opinion as Exhibit 5 to the Registration Statement. Very truly yours, By: /s/ Peter L. Rossiter ----------------------------- Peter L. Rossiter Executive Vice President, General Counsel and Secretary