Exhibit 15

November 3, 2016

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Commissioners:

We are aware that our report dated November 3, 2016 on our review of interim financial information of W. R. Grace & Co. (the "Company") included in the Company's quarterly report on Form 10-Q for the quarter ended September 30, 2016 is incorporated by referencein its Registration Statements on Form S-8 dated May 12, 2000, April 28, 2011, May 2, 2013, and February 27, 2014.

Very truly yours,

/s/ PricewaterhouseCoopers LLP

Baltimore, Maryland