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                                                                   Exhibit 10.24


May 30, 2001

Alan E. Dow, Ph.D.
4425 Shorepointe Way
San Diego, CA 92130-8636

Dear Alan:

         It is with great pleasure that we present our offer to you of the
position of Vice President and General Counsel of Vical Incorporated, (the
"Company"), effective no later than June 15, 2001. We are all delighted about
the prospect of your joining our Senior Management team.

         This letter sets forth the basic terms and conditions of your
employment with the Company. By signing this letter, you will be agreeing to
these terms:

         1.       DUTIES AND SCOPE OF EMPLOYMENT.

         (a)      POSITION. The Company agrees to employ you as Vice President
and General Counsel. You will report to the Chief Executive Officer of the
Company and have the powers and duties commensurate with such position.

         (b)      OBLIGATIONS. During the term of your employment, you will
devote your full business efforts and time to the Company and its subsidiaries
(if any). You will not render services to any other person or entity without the
express prior approval of the Chief Executive Officer. During your employment,
you will not engage, directly or indirectly, in any other business activity
(whether or not pursued for pecuniary advantage) that is or may be competitive
with the Company; provided that you may own less than one percent of the
outstanding securities of any publicly-traded corporation.

         2.       COMPENSATION.

         (a)      SALARY. During your employment, the Company agrees to pay you
as compensation for your services a base salary at the annual rate of $230,000
or at such higher rate as the Company may determine from time to time. Such
salary will be payable in accordance with the Company's standard payroll
procedures. (The annual compensation specified in this Section 2(a), together
with any increases in such compensation that the Company may grant from time to
time, is referred to in this Agreement as "Base Compensation.")

         (b)      BONUS. You will be eligible for a performance-based annual
cash bonus, at the discretion of the Board of Directors, targeted at 10% to 20%
of your Base Compensation during 2001. Bonuses are generally proposed in January
of the following year and, if approved by the Board of Directors, are paid out
in the following February.


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Dr. Alan E. Dow
May 30, 2001
Page 2


         3.       EMPLOYEE BENEFITS.


         (a)      COMPANY BENEFITS. During the term of your employment, you will
be eligible to participate in the employee benefit plans maintained by the
Company, subject in each case to the generally applicable terms and conditions
of the plan in question and to the determinations of any person or committee
administering such plan. The benefits may be changed from time to time by the
Company. Current employee benefits are described in the enclosed benefit
summary.

         (b)      CALIFORNIA BAR. You will be entitled to take a paid leave of
absence for the purpose of studying for and taking the California State Bar
examination, not to exceed an aggregate of six weeks prior to and the days of
the examination. The Company will reimburse you for the cost of a Bar
examination review course and the examination fee.

         4.       BUSINESS EXPENSES. During your employment, you will be
authorized to incur necessary and reasonable travel, entertainment and other
business expenses in connection with your duties hereunder. The Company will
reimburse you for such expenses upon presentation of an itemized account and
appropriate supporting documentation, all in accordance with the Company's
generally applicable policies.

         5.       STOCK OPTION. The Company will grant to you a stock option
(such option to be an incentive stock option to the extent permitted by law) to
purchase from the Company 80,000 shares of the Company's common stock (the
"Shares"). The exercise price of your stock option will be equal to the fair
market value on the date of the grant. Your stock option will be granted
pursuant to the Stock Incentive Plan of Vical Incorporated and will be subject
to the terms and conditions of the Plan and the Company's form of stock option
agreement, a copy of which is enclosed. Your stock options will vest (become
exercisable) on a quarterly basis over a four-year period, subject to a one-year
"cliff" vesting provision.

         6.       PROPRIETARY INFORMATION AND INVENTIONS AGREEMENT. You will be
required to sign and abide by the terms of the Company's Employee's Proprietary
Information and Inventions Agreement, a copy of which is enclosed.

         7.       IMMIGRATION DOCUMENTATION. Please be advised that your
employment is contingent on your ability to prove your identity and
authorization to work in the United States. You must comply with the Immigration
and Naturalization Service's employment verification requirements.

         8.       TERM AND TERMINATION OF EMPLOYMENT.

         (a)      "AT WILL" EMPLOYMENT. Your employment with the Company is "at
will" and not for a specified term and may be terminated by you or the Company
at any time for any reason, with or without cause. Except as expressly provided
in subsection (c) below, upon a termination of your employment, you will only be
entitled to the compensation, benefits and


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Dr. Alan E. Dow
May 30, 2001
Page 3


reimbursements described in Section 2, 3 and 4 for the period preceding the
effective date of the termination.

         (b)      DEFINITIONS. For all purposes under this Agreement,

                  (i)      "Good Reason" shall mean (A) you have incurred a
         material reduction in your authority or responsibility, (B) a more than
         25 percent reduction in Base Compensation or (C) a material breach of
         this Agreement by the Company;

                  (ii)     "Cause" shall mean (A) a failure to perform your
         duties hereunder, other than a failure resulting from complete or
         partial incapacity due to physical or mental illness or impairment, (B)
         gross misconduct or fraud or (C) conviction of, or a plea of "guilty"
         or "no contest" to, a felony.

                  (iii)    "Disability" shall mean that you, at the time your
         employment is terminated, have performed substantially none of your
         duties under this Agreement for a period of not less than three
         consecutive months as the result of your incapacity due to physical or
         mental illness.

         (c)      SALARY CONTINUATION. Subject to subsection (d) below, the
Company will continue to pay your Base Compensation (at the annual rate then in
effect) for up to six months following a termination of your employment if,
prior to the fourth annual anniversary of the commencement of your employment:

                  (i)      the Company terminates your employment without your
         consent for any reason other than Cause or Disability; or

                  (ii)     you voluntarily resign your employment for Good
         Reason.

The payments under this subsection (c) will cease in the event of your death. In
order to receive your salary continuation, you will be required to sign a
release in a form acceptable to the Company, of any and all claims that you may
have against the Company.

         (d)      MITIGATION. The payments under subsection (c) above shall be
reduced on a dollar-for-dollar basis by any other compensation earned by you for
personal services performed as an employee or independent contractor during the
six-month period following the termination of your employment, including
(without limitation) deferred compensation. You will apply your best efforts to
seek and obtain other employment or consulting engagements, whether on a full-
or part-time basis, during such six-month period in order to mitigate the
Company's obligations under subsection (c) above. At reasonable intervals, you
will report to the Company with respect to such efforts and any compensation
earned during such six-month period.


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Dr. Alan E. Dow
May 30, 2001
Page 4


         9.       DISPUTE RESOLUTION. You and the Company ("the parties ") agree
that any dispute arising out of or related to your employment shall be resolved
as provided in the Dispute Resolution Procedures attached hereto as Exhibit A.

         Please note that this Agreement supersedes any prior agreements,
representations or promises of any kind, whether written, oral, express or
implied between the parties hereto with respect to the subject matters herein,
and it, together with your stock option agreement and Employee's Proprietary
Information and Inventions Agreement, constitutes the full, complete and
exclusive agreement between you and the Company with respect to the subject
matters herein. This Agreement cannot be changed unless in writing, signed by
you and an authorized officer of the Company. If any term of this Agreement is
held to be invalid, void or unenforceable, the remainder of this Agreement shall
remain in full force and effect and shall in no way be affected, and the parties
will use their best efforts to find an alternative way to achieve the same
result.

         This offer letter may be executed in two or more counterparts, each of
which shall be deemed an original and all of which together shall constitute one
and the same instrument. This Agreement is governed by California law without
regard to its choice of law provisions.

         To indicate your acceptance of this offer of employment, please sign
below and return one signed copy to me no later than May 31, 2001.

                                        Sincerely,

                                        VICAL INCORPORATED

                                        By /s/ Vijay B. Samant
                                          --------------------------------------
                                          Vijay B. Samant
                                          President and Chief Executive Officer


ACCEPTED AND AGREED
This 30th day of May, 2001:
/s/ Alan E. Dow
- ------------------------
Alan E. Dow, Ph.D.


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                                    EXHIBIT A

                          DISPUTE RESOLUTION PROCEDURE

         You and the Company ("the parties ") agree that any dispute arising out
of or related to your employment shall be resolved by binding arbitration,
except where the law specifically forbids the use of arbitration as a final and
binding remedy, or where subsection (g) below specifically allows a different
remedy.

         (a)      The complainant shall provide the other party with a written
statement of the claim identifying any supporting witnesses or documents and the
requested relief.

         (b)      The respondent shall furnish a statement of the relief, if
any, that it is willing to provide, and identify supporting witnesses or
documents. If the matter is not resolved, the parties shall submit the dispute
to nonbinding mediation, paid for by the Company, before a mediator to be
selected by the parties.

         (c)      If the matter is not resolved through mediation, the parties
agree that the dispute shall be resolved by binding arbitration. If the parties
are unable to jointly select an arbitrator, they will obtain a list of
arbitrators from the Federal Mediation and Conciliation Service and select an
arbitrator by striking names from that list.

         (d)      The arbitrator shall have the authority to determine whether
the conduct complained of in subsection (a) of this Section 9 violates the
complainant's rights and, if so, to grant any relief authorized by law; subject
to the exclusions of subsection (g) below. The arbitrator shall not have the
authority to modify, change or refuse to enforce the terms of any employment
agreement between the parties, or change any lawful policy or benefit plan.

         (e)      The Company will bear the costs of the arbitration if you
prevail. If the Company prevails, you will pay half the cost of the arbitration
or $500, whichever is less. Each party shall pay its own attorneys fees, unless
the arbitrator orders otherwise pursuant to applicable law.

         (f)      Arbitration shall be the exclusive final remedy for any
dispute between the parties, such as disputes involving claims for
discrimination or harassment (such as claims under the Fair Employment and
Housing Act, Title VII of the Civil Rights Act of 1964, the Americans with
Disabilities Act, or the Age Discrimination in Employment Act), wrongful
termination, breach of contract, breach of public policy, physical or mental
harm or distress or any other disputes, and the parties agree that no dispute
shall be submitted to arbitration where the complainant has not complied with
the preliminary steps provided for in sections (a) and (b) above.

         (g)      The parties agree that the arbitration award shall be
enforceable in any court having jurisdiction to enforce this Agreement, so long
as the arbitrator's findings of fact are supported by substantial evidence on
the whole and the arbitrator has not made errors of law; however, either party
may bring an action in a court of competent jurisdiction regarding or related to
matters involving the Company's confidential, proprietary or trade secret


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information, or regarding or related to inventions that you may claim to have
developed prior to joining the Company or after joining the Company, pursuant to
California Labor Code Section 2870 ("Disputes Related to Inventions"). The
parties further agree that for Disputes Related to Inventions that the parties
have elected to submit to arbitration, each party retains the right to seek
preliminary injunctive relief in court in order to preserve the status quo or
prevent irreparable injury before the matter can be heard in arbitration.


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