State Street (STT) 10-Q 2001 Q2 Quarterly report

EXHIBIT 15

STATE STREET CORPORATION

Independent Accountants’ Acknowledgement Letter

The Stockholders and Board of Directors

State Street Corporation

We are aware of the incorporation of reference in Registration Statements (Form S-3: Nos. 333-16987, 333-34516, 333-34516-01, 333-34516-02, 333-34516-03, 333-2143, 33-49885, 333-49143, 333-49143-01, 333-49143-02, 333-49143-03 and 333-53854 and Form S-8: Nos. 333-65281, 333-46678, 333-36409, 333-16979, 33-57359, 33-38672, 33-38671, 33-2882, 2-93157, 2-88641, 2-68696 and 2-68698), of our report dated July 17, 2001 relating to the unaudited consolidated interim financial statements of State Street Corporation which are included in its Form 10-Q for the quarter ended June 30, 2001.

ERNST & YOUNG LLP

Boston, Massachusetts

August 2, 2001