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                          January 5, 2021

       Stephen Moore
       General Counsel
       Personalis, Inc.
       1330 O   Brien Drive
       Menlo Park, California 94025

                                                        Re: Personalis, Inc.
                                                            Registration
Statement on Form S-3
                                                            Filed December 30,
2020
                                                            File No. 333-251824

       Dear Mr. Moore:

              This is to advise you that we have not reviewed and will not
review your registration
       statement.

               Please refer to Rules 460 and 461 regarding requests for
acceleration. 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.

                                                        Please contact Courtney
Lindsay at (202) 551-7237 with any questions.




                          Sincerely,


                          Division of Corporation Finance

                          Office of Life Sciences