March 23, 1999

                                                                       EXHIBIT 5


Securities and Exchange Commission
Judiciary Plaza
450 Fifth Street, N.W.
Washington, D.C. 20549-1004


     Re:  Northern Trust Corporation:  Registration Statement on
          Form S-8 Regarding Registration of Additional Participations
          in The Northern Trust Company Thrift-Incentive Plan

Ladies and Gentlemen:

     I am Executive Vice President and General Counsel 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 $100,000,000 of
participations in The Northern Trust Company Thrift-Incentive Plan (the "Plan")
consisting of shares of common stock of the Corporation, $1.66 2/3 par value per
share, including the associated Preferred Stock Purchase Rights (collectively,
the "Stock"). 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 on 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.

     In addition, Northern Trust Corporation has submitted the Plan to the
Internal Revenue Service and has made all changes required by the IRS in order
to qualify the Plan and undertakes that it will do so in the future with respect
to any amendments that could affect the Plan's qualification.

     I hereby consent to the filing of this opinion as Exhibit 5 to the
Registration Statement.

                       
                                                    Very truly yours,


                                                    /s/ Peter L. Rossiter
                                                    ---------------------
                                                    Peter L. Rossiter
                                                    Executive Vice President
                                                    and General Counsel