SecProbe.io

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 P ERSONALIS , I NC .
 6600 Dumbarton Circle Fremont,
California 94555 VIA EDGAR April 1, 2025
 U.S. Securities and Exchange Commission Division of Corporation
Finance Office of Industrial Applications and Services 100
F Street, N.E. Washington, D.C. 20549 Attn: Jane Park

 Re:
 Personalis, Inc.
 Registration Statement on Form S-3
 File No. 333-285379

 Acceleration Request

 Requested Date:

 April 3, 2025

 Requested Time:

 5:00 p.m. Eastern Time
 Ladies and Gentlemen: In
accordance with Rule 461 under the Securities Act of 1933, as amended, Personalis, Inc. hereby requests that the Securities and Exchange Commission take appropriate action to cause the above-referenced Registration Statement on Form S-3 (File No. 333-285379) (the “ Registration Statement ”) to become effective on Thursday, April 3, 2025, at 5:00 p.m. Eastern Time, or as
soon thereafter as is practicable. Once the Registration Statement has been declared effective, please orally confirm that event with Laura Berezin or
Asa Henin of Cooley LLP at (206) 452-8775 or (858) 550-6104. Thank you for your assistance with this matter.

 Sincerely,

 PERSONALIS, INC.

 By:

 /s/ Aaron Tachibana

 Aaron Tachibana

 Chief Financial Officer and Chief Operating Officer

March 6, 2025
Christopher Hall
Chief Executive Officer
Personalis, Inc.
6600 Dumbarton Circle
Fremont, California, 94555
Re:Personalis, Inc.
Registration Statement on Form S-3
Filed February 27, 2025
File No. 333-285379
Dear Christopher Hall:
            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 Jane Park at 202-551-7439 with any questions.
Sincerely,
Division of Corporation Finance
Office of Industrial Applications and
Services
cc:Asa M. Henin, Esq.

September 9, 2024
Christopher Hall
President and Chief Executive Officer
Personalis, Inc.
6600 Dumbarton Circle
Fremont, CA, 94555
Re:Personalis, Inc.
Registration Statement on Form S-3
Filed August 30, 2024
File No. 333-281886
Dear Christopher Hall:
            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 Robert Augustin at 202-551-8483 with any questions.
Sincerely,
Division of Corporation Finance
Office of Industrial Applications and
Services
cc:Laura Berezin

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 PERSONALIS, INC.

6600 Dumbarton Circle

 Fremont,
California 94555

 VIA EDGAR

 September 9, 2024

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 Office of Industrial Applications and Services

 100
F Street, N.E.

 Washington, D.C. 20549

 Attn: Robert Augustin

Re:
 Personalis, Inc.

Registration Statement on Form S-3

File No. 333-281886

Acceleration Request

Requested Date:

September 11, 2024

Requested Time:

4:00 p.m. Eastern Time

 Ladies and Gentlemen:

 In
accordance with Rule 461 under the Securities Act of 1933, as amended, Personalis, Inc. hereby requests that the Securities and Exchange Commission take appropriate action to cause the above-referenced Registration Statement on Form S-3 (File No. 333-281886) (the “Registration Statement”) to become effective on Wednesday, September 11, 2024, at 4:00 p.m. Eastern Time, or
as soon thereafter as is practicable.

 Once the Registration Statement has been declared effective, please orally confirm that event with Laura Berezin or
Asa Henin of Cooley LLP, our outside counsel, at (206) 452-8775 or (858) 550-6104. Thank you for your assistance with this matter.

Sincerely,

PERSONALIS, INC.

By:

/s/ Aaron Tachibana

Aaron Tachibana

Chief Financial Officer and Chief Operating Officer

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 PERSONALIS, INC.

6600 Dumbarton Circle

 Fremont,
California 94555

 VIA EDGAR

 January 5, 2024

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 Office of Industrial Applications and Services

 100
F Street, N.E.

 Washington, D.C. 20549

 Attn: J. Conlon
Danberg

Re:
 Personalis, Inc.

Registration Statement on Form S-3

File No. 333-276204

     Acceleration Request

     Requested Date:

 January 9, 2024

     Requested Time:

 4:00 p.m. Eastern Time

 Ladies and Gentlemen:

 In
accordance with Rule 461 under the Securities Act of 1933, as amended, Personalis, Inc. hereby requests that the Securities and Exchange Commission take appropriate action to cause the above-referenced Registration Statement on Form S-3 (File No. 333-276204) (the “Registration Statement”) to become effective on Tuesday, January 9, 2024, at 4:00 p.m. Eastern Time, or as
soon thereafter as is practicable.

 Once the Registration Statement has been declared effective, please orally confirm that event with Laura Berezin or
Asa Henin of Cooley LLP, our outside counsel, at (206) 452-8775 or (858) 550-6104. Thank you for your assistance with this matter.

Sincerely,

 PERSONALIS, INC.

By:

 /s/ Aaron Tachibana

Aaron Tachibana

 Chief Financial Officer and Chief

 Operating
Officer

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 PERSONALIS, INC.

6600 Dumbarton Circle

 Fremont,
California 94555

 VIA EDGAR

 January 4, 2024

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 Office of Industrial Applications and Services

 100
F Street, N.E.

 Washington, D.C. 20549

 Attn: J. Conlon
Danberg

Re:

Personalis, Inc.

Registration Statement on Form S-3

File No. 333-276206

Acceleration Request

Requested Date:

January 8, 2024

Requested Time:

4:00 p.m. Eastern Time

 Ladies and Gentlemen:

 In
accordance with Rule 461 under the Securities Act of 1933, as amended, Personalis, Inc. hereby requests that the Securities and Exchange Commission take appropriate action to cause the above-referenced Registration Statement on Form S-3 (File No. 333-276206) (the “Registration Statement”) to become effective on Monday, January 8, 2024, at 4:00 p.m. Eastern Time, or as
soon thereafter as is practicable.

 Once the Registration Statement has been declared effective, please orally confirm that event with Laura Berezin or
Asa Henin of Cooley LLP, our outside counsel, at (206) 452-8775 or (858) 550-6104. Thank you for your assistance with this matter.

Sincerely,

PERSONALIS, INC.

By:

 /s/ Aaron Tachibana

Aaron Tachibana

Chief Financial Officer and Chief Operating Officer

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 Laura Berezin

 +1 206 452 8775

 lberezin@cooley.com

 January 4, 2024

VIA EDGAR

 U.S. Securities and Exchange Commission

 Division of Corporation Finance

 Office of Industrial
Applications and Services

 100 F Street, N.E.

 Washington,
D.C. 20549

 Attn: J. Conlon Danberg

RE:
 Personalis, Inc.

Registration Statement on Form S-3

Filed December 21, 2023

File No. 333-276204

Ladies and Gentlemen:

 On behalf of Personalis,
Inc. (the “Company”), we are providing this letter pursuant to our oral conversations with the staff of the U.S. Securities and Exchange Commission’s Division of Corporation Finance (the “Staff”)
on December 29, 2023 and January 3, 2024 with respect to the Company’s Registration Statement on Form S-3 (File No. 333-276204), filed on
December 21, 2023 (the “Registration Statement”).

 The table below sets forth the aggregate market value of
shares of the Company’s outstanding common stock held by non-affiliates of the Company as of December 21, 2023, calculated in accordance with General Instruction I.B.1 of Form S-3. Other than the Company’s directors and executive officers, the Company has no other “affiliates” as that term is defined in Rule 405 under the Securities Act of 1933, as amended.

 Shares Outstanding

50,182,691

 Shares Issued and Beneficially Owned by Affiliates

381,133

 Shares Outstanding Held by Non-Affiliates

49,801,558

 Closing Price on November 27, 2023

$
1.80

 Public Float

$
89,642,804

 Pursuant to the above, the Company is eligible to offer securities under the Registration Statement pursuant
to General Instruction I.B.1 of Form S-3.

 We request that the Staff contact Laura Berezin or
Asa Henin of Cooley LLP, outside counsel to the Company, at (206) 452-8775 or (858) 550-6104, with any questions or comments regarding this letter.

Cooley LLP    1700 Seventh Avenue    Suite 1900    Seattle,
WA    98101-1355

 t: +1 206 452 8700   f: +1 206 452 8800   cooley.com

 Laura Berezin

 +1 206 452 8775

 lberezin@cooley.com

 Sincerely,

Cooley LLP

By:

 /s/ Laura Berezin

Laura Berezin

cc:
 Christopher Hall, Personalis, Inc.

Aaron Tachibana, Personalis, Inc.

Stephen Moore, Personalis, Inc.

Asa Henin, Cooley LLP

United States securities and exchange commission logo
January 3, 2024
Christopher Hall
President and Chief Executive Officer
Personalis, Inc.
6600 Dumbarton Circle
Fremont, California, 94555
Re:Personalis, Inc.
Registration Statement on Form S-3
Filed December 21, 2023
File No. 333-276204
Dear Christopher Hall:
            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 Conlon Danberg at 202-551-4466 with any questions.
Sincerely,
Division of Corporation Finance
Office of Industrial Applications and
Services
cc:       Asa M. Henin, Esq.

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 PERSONALIS, INC.

1330 O’Brien Drive

 Menlo
Park, California 94025

 (650) 752-1300

January 6, 2021

 VIA EDGAR

United States Securities and Exchange Commission

 Division of
Corporation Finance

 Office of Life Sciences

 100 F Street,
N.E.

 Washington, D.C. 20549

Re:
 Personalis, Inc.

Registration Statement on Form S-3

Filed December 30, 2020

File No. 333-251824

Ladies and Gentlemen:

 In accordance with Rule 461 under the
Securities Act of 1933, as amended, the undersigned registrant (the “Registrant”) hereby requests that the Securities and Exchange Commission (the “Commission”) take appropriate action to cause the
Registration Statement on Form S-3 (File No. 333-251824) (the “Registration Statement”) to become effective on Friday, January 8, 2021,
at 4:00 p.m., Eastern Time, or as soon as practicable thereafter, or at such later time as the Registrant may orally request via telephone call to the staff of the Commission (the “Staff”). The Registrant hereby authorizes
Mike Tenta of Cooley LLP, counsel to the Registrant, to make such request on its behalf.

 Once the Registration Statement has been declared effective,
please orally confirm that event with Mike Tenta of Cooley LLP, counsel to the Registrant, at (650) 843-5636, or, in his absence, Jacob B. Hanna of Cooley LLP at (415)
693-2202.

 In connection with this request, the Registrant acknowledges that:

•

 should the Commission or the Staff, acting pursuant to delegated authority, declare the filing effective, it does
not foreclose the Commission from taking any action with respect to the filing;

•

 the action of the Commission or the Staff, acting pursuant to delegated authority, in declaring the filing
effective, does not relieve the Registrant from its full responsibility for the adequacy and accuracy of the disclosure in the filing; and

•

 the Registrant may not assert Staff comments and the declaration of effectiveness as a defense in any proceeding
initiated by the Commission or any person under the federal securities laws of the United States.

 Very truly yours,

PERSONALIS, INC.

By:

/s/ John West

Name:

John West

Title:

President and Chief Executive Officer

cc:
 Aaron Tachibana, Chief Financial Officer, Personalis, Inc.

Stephen Moore, General Counsel and Corporate Secretary, Personalis, Inc.

Mike Tenta, Cooley LLP

 Jacob B.
Hanna, Cooley LLP

United States securities and exchange commission logo
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

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 PERSONALIS, INC.

1330 O’Brien Drive

 Menlo
Park, California 94025

 (650) 752-1300

July 8, 2020

 VIA EDGAR

United States Securities and Exchange Commission

 Division of
Corporation Finance

 Office of Life Sciences

 100 F Street,
N.E.

 Washington, D.C. 20549

Re:
 Personalis, Inc.

Registration Statement on Form S-3

Filed July 2, 2020

File No. 333-239649

Ladies and Gentlemen:

 In accordance with Rule 461 under the
Securities Act of 1933, as amended, the undersigned registrant (the “Registrant”) hereby requests that the Securities and Exchange Commission (the “Commission”) take appropriate action to cause the
Registration Statement on Form S-3 (File No. 333-239649) (the “Registration Statement”) to become effective on Friday, July 10, 2020,
at 4:00 p.m., Eastern Time, or as soon as practicable thereafter, or at such later time as the Registrant may orally request via telephone call to the staff of the Commission (the “Staff”). The Registrant hereby authorizes
Peter Mandel of Cooley LLP, counsel to the Registrant, to make such request on its behalf.

 Once the Registration Statement has been declared effective,
please orally confirm that event with Peter Mandel of Cooley LLP, counsel to the Registrant, at (415) 693-2102, or, in his absence, Mike Tenta of Cooley LLP at (650)
843-5636.

 In connection with this request, the Registrant acknowledges that:

•

 should the Commission or the Staff, acting pursuant to delegated authority, declare the filing effective, it does
not foreclose the Commission from taking any action with respect to the filing;

•

 the action of the Commission or the Staff, acting pursuant to delegated authority, in declaring the filing
effective, does not relieve the Registrant from its full responsibility for the adequacy and accuracy of the disclosure in the filing; and

•

 the Registrant may not assert Staff comments and the declaration of effectiveness as a defense in any proceeding
initiated by the Commission or any person under the federal securities laws of the United States.

Very truly yours,

PERSONALIS, INC.

By:

 /s/ John West

Name:

John West

Title:

President and Chief Executive Officer

cc:
 Aaron Tachibana, Chief Financial Officer, Personalis, Inc.

Stephen Moore, General Counsel and Corporate Secretary, Personalis, Inc.

Mike Tenta, Cooley LLP

 Peter
Mandel, Cooley LLP

United States securities and exchange commission logo
July 7, 2020
John West
President and Chief Executive Officer
Personalis, Inc.
1330 O’Brien Drive
Menlo Park, CA 94025
Re:Personalis, Inc.
Registration Statement on Form S-3
Filed July 2, 2020
File No. 333-239649
Dear Mr. West:
            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 Alan Campbell at 202-551-4224 with any questions.
Sincerely,
Division of Corporation Finance
Office of Life Sciences
cc:       Peter Mandel

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CORRESP

 PERSONALIS, INC.

1330 O’Brien Drive

 Menlo
Park, CA 94025

 June 17, 2019

 VIA EDGAR

 U.S. Securities and Exchange Commission

 Division
of Corporation Finance

 100 F Street, N.E.

Washington, D.C. 20549

Attn:
 James Giugliano

 Craig Arakawa

 Michael Killoy

 Brigitte Lippmann

Re:
 Personalis, Inc.

 Registration Statement on Form S-1, as amended (File No. 333-231703)

 Request for Acceleration of Effective Date

Ladies and Gentlemen:

 Pursuant
to Rule 461 of the General Rules and Regulations under the Securities Act of 1933, as amended, Personalis, Inc. (the “Company”) hereby requests that the Securities and Exchange Commission (the “Commission”)
accelerate the effective date of the above-referenced Registration Statement on Form S-1 (as amended to date, the “Registration Statement”) and declare the Registration Statement
effective as of 4:00 p.m. Eastern time, on June 19, 2019, or as soon thereafter as possible, or at such other time as the Registrant may request by telephone to the Staff. The Registrant hereby authorizes each of Michael Tenta and Peter
Mandel of Cooley LLP, counsel to the Registrant, to make such request on its behalf.

 Once the Registration Statement has been
declared effective, please orally confirm that event with Michael Tenta of Cooley LLP at (650) 843-5636 or, in his absence, Peter Mandel of Cooley LLP at
(415) 693-2102.

 Under separate cover, you will receive today a letter from the managing
underwriters of the proposed offering joining in the Company’s request for acceleration of the effectiveness of the Registration Statement.

[Signature page follows]

 Very truly yours,

Personalis, Inc.

/s/ John West

By:

John West

Title:

President and Chief Executive Officer

 [Signature Page to Acceleration Request]

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 Morgan Stanley & Co. LLC

1585 Broadway

 New York, New York 10036

BofA Securities, Inc.

 One Bryant Park

New York, New York 10036

 Cowen and Company, LLC

599 Lexington Avenue, 20th Floor

 New York, New York 10022

June 17, 2019

 VIA EDGAR

U.S. Securities and Exchange Commission

 Division of Corporation
Finance

 100 F Street, N.E.

 Washington, D.C. 20549

 Attn:

 James Giugliano

 Craig Arakawa

 Michael Killoy

 Brigitte Lippmann

Re:

Personalis, Inc.

Registration Statement on Form S-1, as amended (File No. 333-231703)

Request for Acceleration of Effective Date

 Ladies and Gentlemen:

In accordance with Rule 461 under the Securities Act of 1933, as amended (the “Act”), we, as representatives of the several
underwriters, hereby join in the request of Personalis, Inc. (the “Company”) for acceleration of the effective date of the above-named Registration Statement so that it becomes effective at 4:00 PM, Eastern Time, on June 19,
2019, or as soon thereafter as practicable, or at such other time as the Company or its outside counsel, Cooley LLP, request by telephone that such Registration Statement be declared effective.

Pursuant to Rule 460 under the Act, we, as representatives of the several underwriters, wish to advise you that we have carried out the
following distribution of the Company’s preliminary prospectus dated June 7, 2019:

(i)
 Dates of distribution: June 7, 2019 through the date hereof

(ii)
 Number of prospective underwriters to which the preliminary prospectus was furnished: 4

(iii)
 Number of prospectuses furnished to investors: approximately 2,200

(iv)
 Number of prospectuses distributed to others, including the Company, the Company’s counsel, independent
accountants, and underwriters’ counsel: approximately 50

 We, the undersigned, as representatives of the several
underwriters, have complied and will comply, and we have been informed by the participating underwriters that they have complied and will comply, with the requirements of Rule 15c2-8 under the Securities
Exchange Act of 1934, as amended.

 [Signature page follows]

Very truly yours,

 MORGAN STANLEY & CO. LLC

BOFA SECURITIES, INC.

 COWEN AND COMPANY, LLC

 Acting severally on behalf of themselves and the

several Underwriters

MORGAN STANLEY & CO. LLC

By:

 /s/ Chris Rigoli

Name:

Chris Rigoli

Title:

Vice President

BOFA SECURITIES, INC.

By:

 /s/ Michele A.H. Allong

Name:

Michele A.H. Allong

Title:

Authorized Signatory

COWEN AND COMPANY, LLC

By:

 /s/ Bill Follis

Name:

Bill Follis

Title:

Managing Director

 [Signature Page to Acceleration Request]

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 *FOIA Confidential Treatment Request*

Confidential Treatment Requested by Personalis, Inc.

in connection with Registration Statement on Form S-1

 Michael E. Tenta

 +1 650 843
5636

 mtenta@cooley.com

CERTAIN PORTIONS OF THIS LETTER HAVE BEEN OMITTED FROM THE VERSION FILED VIA EDGAR. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT
TO THE OMITTED PORTIONS. INFORMATION THAT WAS OMITTED IN THE EDGAR VERSION HAS BEEN NOTED IN THIS LETTER WITH A PLACEHOLDER IDENTIFIED BY THE MARK “[***]”.

June 4, 2019

 U.S. Securities and Exchange Commission

Division of Corporation Finance

 100 F Street, N.E.

Washington, D.C. 20549

Attn:
 James Giugliano

Craig Arakawa

 Michael Killoy

 Brigitte Lippmann

Re:
 Registration Statement on Form S-1

Filed May 23, 2019

File No. 333-231703

Ladies and Gentlemen:

 On behalf of Personalis,
Inc. (“Personalis” or the “Company”), we are supplementally providing the staff (the “Staff”) of the Securities and Exchange Commission (the
“Commission”) with information regarding the proposed price range of the shares of the Company’s common stock to be offered in the proposed initial public offering (“IPO”) pursuant to the
Company’s Registration Statement on Form S-1 (File No. 333-231703) filed with the Commission on May 23, 2019 (the “Registration
Statement”). We are providing this letter in response to comment 5 from the Staff received by letter dated April 23, 2019 relating to the Draft Registration Statement originally confidentially submitted on March 27, 2019.

Because of the commercially sensitive nature of information contained herein, this submission is accompanied by a request for confidential
treatment for selected portions of this letter. The Company has filed a separate letter with the Office of Freedom of Information and Privacy Act Operations in connection with the confidential treatment request, pursuant to Rule 83 of the
Commission’s Rules on Information and Requests, 17 C.F.R. § 200.83. For the Staff’s reference, we have enclosed a copy of the Company’s letter to the Office of Freedom of Information and Privacy Act Operations, as well as a
copy of this correspondence, marked to show the portions redacted from the version filed via EDGAR and for which the Company is requesting confidential treatment.

For the convenience of the Staff, we are providing to the Staff by overnight delivery copies of this letter.

 Cooley LLP 3175 Hanover
Street Palo Alto, CA 94304-1130

 t: (650) 843-5000 f: (650)
849-7400 cooley.com

 U.S. Securities and Exchange Commission

 June 4,
2019

 Page Two

 Confidential Treatment Requested

by Personalis, Inc.

 Preliminary IPO Price Range

The Company supplementally advises the Staff that the Company preliminarily estimates a price range of [***] per share (the
“Preliminary IPO Price Range”) for its IPO, after giving effect to a reverse stock split, pursuant to which each [***] outstanding shares of its capital stock will be combined into one share of capital stock (the
“Proposed Reverse Stock Split”). The Company anticipates effecting the Proposed Reverse Stock Split before commencing marketing efforts for the IPO, and the information contained in this letter gives effect to the Proposed
Reverse Stock Split. As is typical in IPOs, the Preliminary IPO Price Range was not derived using a formal determination of fair value but was determined pursuant to recent discussions between the Company and the underwriters for the IPO. The
Preliminary IPO Price Range has been estimated based, in part, upon current market conditions, the Company’s financial condition and prospects, performance of recent initial public offerings and input received from the lead underwriters,
including discussions that took place during a meeting of the Company’s board of directors (the “Board”) on May 23, 2019, that included representatives of the underwriters.

The Company expects to include the price range and the approved Proposed Reverse Stock Split in an amendment to the Registration Statement
that would be filed shortly before the commencement of the Company’s road show. We are providing this information to you supplementally to facilitate your review process.

Recent Common Stock Valuations

 To assist
the Staff in its evaluation of stock compensation disclosures and certain other matters in the Registration Statement, the Company provides the Staff with the following information in relation to stock options granted during the period from
January 1, 2018 through March 2019:

 Grant period

Number of
shares
underlying
stock options
granted

Per share
exercise
price of
options

* Estimated
fair value per
share of
common
stock

 Quarter 2, 2018

596,875

$
3.80

$
6.12

 Quarter 3, 2018

43,000

$
3.80

$
7.32

 Quarter 4, 2018

746,589

$
7.32

$
9.16

 February 2019

149,000

$
9.16

$
11.72

 March 2019

212,500

$
9.16

$
12.40

*
 The fair values per common share underlying stock options granted between independent third-party valuation
report dates were estimated by interpolating between the common share fair values per the independent third-party valuation reports before and after the date of grant. The Company believes its use of linear interpolation between such valuation dates
is an appropriate methodology by which to determine the fair value per share for financial accounting purposes due to the rapid growth of the Company and because the Company did not identify any single event or series of events that occurred during
the period that would have caused a material change in fair value.

 Cooley LLP 3175 Hanover
Street Palo Alto, CA 94304-1130

 t: (650) 843-5000 f: (650) 849-7400 cooley.com

 U.S. Securities and Exchange Commission

 June 4,
2019

 Page Three

 Confidential Treatment Requested

by Personalis, Inc.

 As stated in the Registration Statement, stock-based compensation expense related to stock
options granted to employees is measured at the date of grant based on the estimated fair value of the award. The Registration Statement describes the Company’s use of the Black-Scholes option-pricing model for these purposes and describes the
significant assumptions used during the years ended December 31, 2017 and 2018 and the three months ended March 31, 2019. The Company will reevaluate each of these assumptions, and update them as appropriate, when granting new equity
awards and in preparing its financial statements for future filings.

 Historical Stock-Based Compensation Expense

The Company’s stock-based compensation expense for the years ended December 31, 2017 and 2018 and the three months ended
March 31, 2019 were approximately $753,000 (2% of total costs and expenses), $1,317,000 (3% of total costs and expenses), and $609,000 (3% of total costs and expenses), respectively.

Stock Option Grants and Common Stock Valuations

The estimated fair value of the common stock underlying stock options was determined at each grant date by the Board and was supported by
periodic independent third-party valuations. The valuations of common stock were determined in accordance with the guidelines outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held-Company Equity
Securities Issued as Compensation (the “Practice Aid”). The methodology used by the third-party valuation specialists to determine the fair value of the Company’s common stock included estimating the fair value of the
enterprise, subtracting the fair value of debt from this enterprise value, and then allocating this value to all of the equity interests using the option pricing method or the probability weighted expected return method. The assumptions used in the
valuation model to determine the estimated fair value of the Company’s common stock as of the grant date of each option are based on numerous objective and subjective factors, combined with management judgment, including the following:

•

 the Company’s stage of development;

•

 progress of the Company’s research and development efforts;

•

 the impact of significant corporate events or milestones;

•

 material risks related to the business;

•

 the Company’s actual operating results and financial condition, including the Company’s level of
available capital resources;

•

 rights, preferences and privileges of the preferred stock relative to those of the common stock;

•

 equity market conditions affecting comparable public companies;

•

 the likelihood and potential timing of achieving a liquidity event for the shares of common stock, such as an
initial public offering given prevailing market and biotechnology sector conditions; and

•

 that the grants involved illiquid securities in a private company.

 Cooley LLP 3175 Hanover
Street Palo Alto, CA 94304-1130

 t: (650) 843-5000 f: (650) 849-7400 cooley.com

 U.S. Securities and Exchange Commission

 June 4,
2019

 Page Four

 Confidential Treatment Requested

by Personalis, Inc.

 Common Stock Valuation Methodologies

The valuations discussed below were performed in accordance with applicable elements of the Practice Aid. The Practice Aid prescribes several
valuation approaches for estimating the value of an enterprise, such as the cost, market and income approaches, and various methodologies for allocating the value of an enterprise to its common stock.

The Practice Aid identifies various available methods for allocating enterprise value across classes and series of capital stock to determine
the estimated fair value of common stock at each valuation date. In accordance with the Practice Aid, the Company considered the following methods:

•

 Option Pricing Method. Under the option pricing method (“OPM”) shares are valued by
creating a series of call options with exercise prices based on the liquidation preferences and conversion terms of each equity class. The estimated fair values of the preferred and common stock are inferred by analyzing these options.

•

 Probability-Weighted Expected Return Method. The probability-weighted expected return method
(“PWERM”) is a scenario-based analysis that estimates value per share based on the probability-weighted present value of expected future investment returns, considering each of the possible outcomes available to the Company,
as well as the economic and control rights of each share class.

•

 Current Value Allocation. Under the current value allocation method (“CVA”) the equity
value is allocated as if the enterprise were to be liquidated on the date of valuation. The distribution waterfall is applied and the values of the securities are calculated. This method is applicable in extremely early ventures and when a
liquidation event is imminent.

•

 Hybrid Method. The hybrid method (“Hybrid Method”) is a hybrid between the PWERM and OPM,
estimating the probability-weighted value across multiple scenarios but using the OPM to estimate the allocation of value within one of more of the scenarios. The hybrid method can be a useful alternative to explicitly modeling all PWERM scenarios
in situations when the company has transparency into one or more near term exits but is unsure what will occur if the current plans fall through.

Based on the Company’s early stage of development and other relevant factors, the Company determined that PWERM, incorporating aspects of
the market and income approaches, was the most appropriate method for estimating the Company’s enterprise value. For common stock valuations performed during December 2017 and September 2018, the independent valuation specialist incorporated
four outcomes, including stay-private, IPO, and two different M&A scenarios. In the IPO and M&A outcomes, a CVA was used at the assumed exit event and the results were present valued using an equity discount rate. In the stay-private
scenario, an OPM was used to allocate the present equity value indication and was incorporated in the PWERM to capture uncertainties of the stay-private scenario. For common stock valuations performed during December 2018 and March 2019, a
multiple-scenario OPM (IPO and no IPO) was used to estimate the Company’s equity value and allocate to the securities outstanding.

 Cooley LLP 3175 Hanover
Street Palo Alto, CA 94304-1130

 t: (650) 843-5000 f: (650) 849-7400 cooley.com

 U.S. Securities and Exchange Commission

 June 4,
2019

 Page Five

 Confidential Treatment Requested

by Personalis, Inc.

 Common Stock Valuations

In determining the estimated fair value of the common stock underlying the stock options granted, the Board considers the most recent
contemporaneous independent third-party valuation of the Company’s common stock and an assessment of additional objective and subjective factors it believes to be relevant as of the grant date. The additional factors considered when determining
any changes in estimated fair value between the most recent contemporaneous valuation and the grant date include, when applicable, the prices paid in the Company’s recent financing transactions, the Company’s stage of development, the
Company’s laboratory, operating and financial performance and business and financial market conditions generally and in the targeted and personalized cancer diagnostic sector. Each of the stock option valuation dates from December 31, 2017
are discussed below.

 December 31, 2017. The Company received an independent third-party valuation of its common
stock as of December 31, 2017 that indicated that the fair value of the common stock on that date was $3.80 per share. This valuation utilized a hybrid version of the PWERM that incorporated aspects of both the market and income approaches to
estimate the Company’s equity value using a 28% equity discount rate. The model incorporated four different outcomes including stay-private, IPO, and two different M&A scenarios. The equity value for the IPO and M&A scenarios was
derived using a CVA at the assumed exit event and allocated using PWERM to the securities outstanding based on their liquidation preferences and other rights. The equity value for the stay-private scenario was allocated under OPM. The weighted
average time to liquidity was 2.38 years and each scenario yielded a different value indication for the common shares. These values were weighted based on the associated probability of each scenario, resulting in a concluded value of each common
share of $5.36. A weighted average discount for lack of marketability of 29% was applied as a result of the Company being privately held, resulting in a fair value of the Company’s common stock of $3.80 per share. The Board determined the
estimated fair value of the Company’s common stock to be $3.80 per share as of December 31, 2017.

September 30, 2018. The Company received an independent third-party valuation of its common stock as of
September 30, 2018 that indicated that the fair value of the common stock on that date was $7.32 per share. This valuation utilized a hybrid version of the PWERM that incorporated aspects of both the market and income approaches to estimate the
Company’s equity value using a 28% equity discount rate. The model incorporated four different outcomes including stay-private, IPO, and two different M&A scenarios. The equity value for the IPO and M&A scenarios was derived using a CVA
at the assumed exit event and allocated using PWERM to the securities outstanding based on their liquidation preferences and other rights. The equity value for the stay-private scenario was allocated under OPM. The weighted average time to liquidity
was 1.44 years and each scenario yielded a different value indication for the common shares. These values were weighted based on the associated probability of each scenario, resulting in a concluded value of each common share of $9.40. A weighted
average discount for lack of marketability of 22% was applied as a result of the Company being privately held, resulting in a fair value of the Company’s common stock of $7.32 per share. Between D

April 23, 2019
John West
Chief Executive Officer
Personalis, Inc.
1330 O’Brien Drive
Menlo Park, CA 94025
Re:Personalis, Inc.
Draft Registration Statement on Form S-1
Submitted March 27, 2019
CIK No. 0001527753
Dear Mr. West:
            We have reviewed your draft registration statement and have the following comments.  In
some of our comments, we may ask you to provide us with information so we may better
understand your disclosure.
            Please respond to this letter by providing the requested information and either submitting
an amended draft registration statement or publicly filing your registration statement on
EDGAR.  If you do not believe our comments apply to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in your response.
            After reviewing the information you provide in response to these comments and your
amended draft registration statement or filed registration statement, we may have additional
comments.
Draft Registration Statement on Form S-1 submitted March 27, 2019
General
1.Please supplementally provide us with copies of all written communications, as defined in
Rule 405 under the Securities Act, that you, or anyone authorized to do so on your behalf,
present to potential investors in reliance on Section 5(d) of the Securities Act, whether or
not they retain copies of the communications
Use of Proceeds, page 63
2.Please state the approximate amount of proceeds you intend to use for each purpose
listed.  See Item 504 of Regulation S-K.

 FirstName LastNameJohn West
 Comapany NamePersonalis, Inc.
 April 23, 2019 Page 2
 FirstName LastNameJohn West
Personalis, Inc.
April 23, 2019
Page 2
Management's Discussion and Analysis of Financial Condition and Results of Operations
Results of Operations, page 77
3.We note your revenues increased 302% from 2017 to 2018.  You state that this increase in
revenues was primarily due to an increase in the volume of samples you tested in relation
to the sequencing and data analysis services you provided to our customers.  Please
discuss in greater detail the underlying reasons for the material increase in revenues, such
as the reasons for in the increase in the volume of samples tested.  Additionally, if
applicable, disclose whether the reasons for the change is a known trend that you
reasonably expect will have a material favorable impact on your revenues.  See Item
303(a)(3) of Regulation S-K.
Principal Stockholders, page 148
4.Please disclose the the address for each 5% beneficial owner.  See Item 403(a) of
Regulation S-K.
Note 2 – Summary of Significant Accounting Policies
Fair Value of Common Stock, page F-13
5.We may have additional comments on your accounting for equity issuances including the
stock options and other share-based compensation. Once you have an estimated offering
price, please provide us an analysis explaining the reasons for the differences between
recent valuations of your common stock leading up to the IPO and the estimated offering
price.
Note 3 - Revenues
Contract Assets and Liabilities, page F-16
6.We note that you received large amounts of deposits from customers in each of the years
presented and that the balances of your contract liabilities have grown from $5.6 million
as of January 1, 2017 to $42.9 million as of December 31, 2018.  We also note your
disclosure on page 13, that $37.3 million of the balance at December 31, 2018 relates to
one customer.  Please address the following points:
•Tell us how you considered the guidance in ASC paragraphs 606-10-32-15 through 19
in determining the transaction price in these contracts and whether a significant
financing component exists.
•Explain to us the substantive business purpose of the large advance payments.
•Tell us how you considered disclosing the growing balances as a potential trend that
may impact your cash from operations in future periods in your discussion of liquidity
and capital resources.

 FirstName LastNameJohn West
 Comapany NamePersonalis, Inc.
 April 23, 2019 Page 3
 FirstName LastName
John West
Personalis, Inc.
April 23, 2019
Page 3
Undertakings, page II-4
7.Please add the undertakings required by Item 512(a)(5)(ii) and Item 512(a)(6) of
Regulation S-K. Item 512(a)(5)(ii) is required for any prospectus filed in reliance on Rule
430C and Item 512(a)(6) is required for any offering that involves an initial distribution of
securities pursuant to Rule 159A.  For guidance, refer to Securities Act Rules Compliance
and Disclosure Interpretation, Question 229.01.
Exhibits
8.Please file the Convertible Promissory Note agreements identified on page 146 as
exhibits.  See Item 601(b)(10) of Regulation S-K.
            You may contact James Giugliano at 202-551-3319 or Craig Arakawa at 202-551-3650 if
you have questions regarding comments on the financial statements and related matters.  Please
contact Michael Killoy at 202-551-7576 or Brigitte Lippmann at 202-551-3713 with any other
questions.
Sincerely,
Division of Corporation Finance
Office of Beverages, Apparel and
Mining
cc:       Peter Mandel