Exhibit 99 November 10, 2000 Securities and Exchange Commission 450 Fifth Street, N.W. Washington, D.C. 20549 Commissioners: We are aware that our report dated October 24, 2000 on our review of interim financial information of Vertex Pharmaceuticals Incorporated (the "Company") as of and for the period ended September 30, 2000 and included in the Company's quarterly report on Form 10-Q for the quarter then ended is incorporated by reference in its registration statements on Forms S-8 (File Nos. 33-48030, 33-48348, 33-65742, 33-93224, 33-12325, 333-27011, 333-56179 and 333-79549) and Form S-3 (File No. 333-37794). Pursuant to Rule 436(c) under the Securities Act of 1933, this report should not be considered a part of the registration statement prepared or certified by us within the meaning of Sections 7 and 11 of that Act. Yours very truly, /s/ PricewaterhouseCoopers LLP Boston, MA