W.R. Grace & Co. (GRA) 10-Q 2017 Q2 Quarterly report

Exhibit 15

July 28, 2017

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Commissioners:

We are aware that our report dated July 28, 2017 on our review of interim financial information of W. R. Grace & Co. for the three and six month periods ended June 30, 2017 and June 30, 2016 and included in the Company's quarterly report on Form 10-Q for the quarter ended June 30, 2017 is incorporated by reference in its Registration Statements on Form S-8 dated May 12, 2000, April 28, 2011, May 2, 2013, February 27, 2014 and February 23, 2017.

Very truly yours,

/s/ PricewaterhouseCoopers LLP

Baltimore, Maryland