August 30, 2018

Andrew Allen, M.D., Ph.D.
President and Chief Executive Officer
Gritstone Oncology, Inc.
5858 Horton Street, Suite 210
Emeryville, CA 94608

       Re: Gritstone Oncology, Inc.
           Registration Statement on Form S-1
           Filed August 23, 2018
           File No. 333-226976

Dear Dr. Allen:

       We have reviewed your registration statement and have the following
comments. In
some of our comments, we may ask you to provide us with information so we may
understand your disclosure.

       Please respond to this letter by amending your registration statement
and providing the
requested information. If you do not believe our comments apply to your facts
circumstances or do not believe an amendment is appropriate, please tell us why
in your

       After reviewing any amendment to your registration statement and the
information you
provide in response to these comments, we may have additional comments.

Registration Statement on Form S-1

Strategic Collaboration with bluebird bio, page 121

1.     We note your disclosure that the collaboration term ends on a
country-by-country basis
       and product candidate-by-product candidate basis based on completion of
all payments
       owed to you by bluebird. Please revise your description of this
agreement to clarify when
       all payments owed to you by bluebird will be completed. Please also file
this agreement
       as an exhibit or tell us why you believe that you are not required to do
so pursuant to Item
       601(b)(10) of Regulation S-K.
 Andrew Allen, M.D., Ph.D.
Gritstone Oncology, Inc.
August 30, 2018
Page 2
Intellectual Property, page 124

2.     We note your disclosure that you have agreements with Sanquin Reagents
B.V. and other
       third parties under which you have rights to certain intellectual
property such as patents or
       patent applications. Please revise your disclosure to specify the
products, product groups
       or technologies to which such patents or patent applications relate, the
type of patent
       protection, the patent expiration dates and the applicable
        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

       Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration

       You may contact Rolf Sundwall at 202-551-3105 or Jim B. Rosenberg at
202-551-3679 if
you have questions regarding comments on the financial statements and related
matters. Please
contact Ada D. Sarmento at 202-551-3798 or Mary Beth Breslin at 202-551-3625
with any other

FirstName LastNameAndrew Allen, M.D., Ph.D.
                                                             Division of
Corporation Finance
Comapany NameGritstone Oncology, Inc.
                                                             Office of
Healthcare & Insurance
August 30, 2018 Page 2
cc:       Brian J. Cuneo, Esq.
FirstName LastName