1 Exhibit (15) April 27, 2001 USG Corporation 125 South Franklin Street Chicago, Illinois 60606 We are aware that USG Corporation has incorporated by reference into previously filed Registration Statement Numbers 33-40136 and 33-64217 on Form S-3 and 33-22581, as amended, 33-22930, 33-36303, 33-52573, 33-52715, 33-63554, and 33-65383 on Form S-8 its Form 10-Q for the quarter ended March 31, 2001, which includes our report dated April 24, 2001, covering the unaudited condensed financial information contained therein. Pursuant to Regulation C of the Securities Act of 1933, these reports are not considered a part of the registration statement prepared or certified by our firm or reports prepared or certified by our firm within the meaning of Sections 7 and 11 of the Act. It should be noted that we have not performed any procedures subsequent to April 24, 2001. Very truly yours, /s/ ARTHUR ANDERSEN LLP ARTHUR ANDERSEN LLP 32