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                                                                    EXHIBIT 10.5

                              EMPLOYMENT AGREEMENT

                  THIS EMPLOYMENT AGREEMENT (the "Agreement") is made and
entered into as of September 4, 2001, by and between Stratagene Holding
Corporation, a Delaware corporation ("Employer"), and Nicholas H. Roelofs
("Executive").

                                    RECITALS

                  Employer wishes to exclusively contract for the managerial and
business skills possessed by Executive, and Executive desires to be employed by
Employer upon the terms and subject to the conditions herein provided.

                              TERMS AND CONDITIONS

                  NOW, THEREFORE, in consideration of the foregoing premises and
the mutual covenants and conditions hereinafter set forth, the parties hereto
agree as follows:

                                    ARTICLE I

                              EMPLOYMENT AND DUTIES

                  1.1      Position and Duties. Executive shall serve as Senior
Vice President of Marketing and Asian Sales, with responsibility for (i)
overseeing Employer's (and its affiliates) marketing and Asian sales functions
and (ii) such other duties as Employer's Chief Executive Officer or Board of
Directors may reasonably prescribe. Executive shall discharge his duties in a
diligent and professional manner. Further, Executive acknowledges and agrees
that Employer may at any time, or from time to time, modify the scope and/or
nature of the responsibilities, duties or reporting relationships of Executive.

                  1.2      Outside Business Activities Precluded. During his
employment, Executive shall devote his full energies, interest, abilities and
productive time to the performance of this Agreement. Executive shall not,
without the prior written consent of Employer, perform

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other services of any kind or engage in any other business activity other than
for Employer (and its affiliated companies), with or without compensation.
Executive shall not, without the prior written consent of Employer, engage or
prepare to engage in any business activity adverse to Employer's interests.
Employer shall not unreasonably withhold its consent where the requested outside
activity does not detract from Executive's ability to devote his full energies,
interest, abilities and productive time to the performance of this Agreement and
does not adversely affect Employer's interests.

                                   ARTICLE II

                                  COMPENSATION

                  2.1      Salary. For Executive's services hereunder, Employer
shall pay as base salary to Executive the amount of $225,000 per year during the
Employment Term (as hereinafter defined), prorated for any year in which this
Agreement is in effect for only a portion of the calendar year. Said base salary
shall be payable in equal installments in conformity with Employer's normal
payroll period. Executive's salary shall be reviewed by Employer from time to
time at its discretion, and Executive shall receive such salary increases, if
any, as Employer, in its sole discretion, shall determine.

                  2.2      Other Benefits. During the Employment Term, Executive
shall be entitled to participate in and receive all other benefits of employment
generally available to Employer's other executive management personnel,
including, but not limited to, inclusion in Employer's retirement plan, medical
plan, disability plan and other similar benefit plans, subject to and on a basis
consistent with the terms, conditions and overall administration of such plans.
Executive shall be entitled to three weeks of paid vacation each year, which
will accrue and be paid out in conformity with Employer's normal vacation pay
practices. Employer may, in its sole discretion,

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grant such additional benefits to Executive from time to time as Employer deems
proper and desirable.

                  2.3      Stock Options. Employer shall provide Executive with
stock options to purchase 75,000 shares of Employer's Common Stock at $6.00 per
share vesting in five equal installments of 15,000 stock options per each full
year of employment pursuant to a Non-Qualified Stock Option Agreement (the
"Non-Qualified Stock Option Agreement") to be executed by Employer and Executive
concurrently herewith in substantially the form attached hereto as Exhibit B.

                  2.4      Expenses. During the first year of the Employment
Term, Executive shall have access to an expense account in the amount of
$50,000, in accordance with the policies and procedures adopted from time to
time by Employer, provided that Executive properly accounts for such business
expenses in accordance with such policies and procedures.

                  2.5      Lock-up in Event of Initial Public Offering.
Executive agrees that, during a period of 180 days from the date of an initial
public offering of Employer's common stock, Executive will not, without the
prior written consent of the underwriter(s) of the initial public offering,
directly or indirectly, sell, offer to sell, grant any option or right for the
sale of, or otherwise dispose of or transfer, any shares of employer's common
stock.

                                   ARTICLE III

                               TERM OF EMPLOYMENT

                  3.1      At-Will Employment. Executive shall at all times be
an "at-will employee" of Employer. The term of this Agreement shall commence on
the date hereof and shall continue until terminated by either Employer or
Executive pursuant to Sections 3.2 through 3.6 of this Agreement, respectively
(the "Employment Term").

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                  3.2      Early Termination by Employer. Executive's employment
may be terminated at any time during the Employment Term by the Chief Executive
Officer or Board of Directors of Employer, for any or no reason and without
Cause (as hereinafter defined), upon delivery of written notice by Employer.
Employer is not required to give Executive any advance notice of termination
which, in the sole discretion of Employer, may be effective immediately upon
delivery of written notice to Executive.

                  3.3      Early Termination by Executive. Executive may
terminate his employment under this Agreement at any time by giving Employer
written notice of his resignation thirty (30) days in advance; provided,
however, the Chief Executive Officer or Board of Directors of Employer may
determine upon receipt of such notice that the effective date of such
resignation shall be immediate or some time prior to the expiration of the
thirty-day (30) notice period.

                  3.4      Termination for Cause. Executive's employment may be
terminated for Cause by the Chief Executive Officer or Board of Directors of
Employer. For these purposes, termination for "Cause" shall mean termination
because of Executive's (a) personal dishonesty or willful material misconduct,
(b) failure to perform his duties or obligations, including failure to meet
deadlines or milestones, (c) committing embezzlement or a felony, or (d)
material breach of this Agreement or Employer's standard Employee Invention and
Proprietary Information Agreement.

                  3.5      Termination Due to Death or Disability. Executive's
employment hereunder shall terminate immediately upon his death. In the event
that by reason of injury, illness or other physical or mental impairment
Executive shall be (a) completely unable to perform his services hereunder for
more than one consecutive month or (b) unable to perform his

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services hereunder for 50% or more of the normal working day throughout two
consecutive months, then Employer may terminate Executive's employment
hereunder. Executive's beneficiaries, estate, heirs, representatives or assigns,
as appropriate, shall be entitled to the proceeds, if any, due under any
Employer-paid life insurance policy held by Executive, as determined by and in
accordance with the terms of any such policy, as well as any vested benefits
such as accrued vacation benefits and stock options.

                                   ARTICLE IV

                    BENEFITS AFTER TERMINATION OF EMPLOYMENT

                  4.1      Continuation. Upon termination of employment under
this Agreement under Section 3.3 (Early Termination by Executive), Section 3.4
(Termination for Cause) or Section 3.5 (Termination Due to Death or Disability),
all salary and benefits of Executive hereunder shall cease immediately.
Executive's beneficiaries, estate, heirs, representatives or assigns, as
appropriate, shall be entitled to the proceeds, if any, due under any
Employer-paid life insurance policy held by Executive, as determined by and in
accordance with the terms of any such policy, as well as any vested benefits
such as accrued vacation benefits and stock options. Upon termination of
employment under this Agreement under Section 3.2 (Early Termination by
Employer) so long as Executive and Employer shall execute and deliver a mutual
general release in a form mutually acceptable in connection therewith, Executive
shall be entitled to receive payments in amounts equal to the continuation of
Executive's base salary for six (6) months from the date of termination;
provided, however, Employer's obligation to continue Executive's base salary
amount shall cease when Executive accepts employment or becomes eligible for
compensation (in the form of cash or securities), comparable to the base salary
provided to Executive hereunder, from some other source in exchange for
Executive's services. In no event,

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however, shall Employer's obligation to Executive under this Section 4.1 exceed
an amount equal to Executive's base-salary for six (6) months minus any
compensation payable to Executive from some other source in exchange for
Executive's services during such six (6) month period. Except as expressly set
forth above, all unvested stock options, if any, granted to Executive shall
cease to vest and be exercisable upon any termination of this Agreement.

                  4.2      Rights Against Employer. The benefits payable under
this Article IV are exclusive, and no amount shall become payable to any person
(including Executive) by reason of termination of employment for any reason,
with or without Cause, except as provided in this Article IV and as described in
Section 3.5 (Termination Due to Death or Disability). Employer shall not be
obligated to segregate any of its assets or procure any investment in order to
fund the benefits payable under this Article IV.

                                    ARTICLE V

               CONFIDENTIAL INFORMATION AND CONFLICTS OF INTEREST

                  5.1      Employee Invention and Proprietary Information
Agreement. Employer and Executive shall execute concurrently herewith an
Employee Invention and Proprietary Information Agreement in substantially the
form attached hereto as Exhibit A.

                  5.2      Conflicts of Interest. Executive, while employed or
receiving severance payments hereunder, shall not take any action without
Employer's prior written consent to establish, form or become employed by
another business, other than interviewing with a prospective employer on
Executive's own time. Should Executive violate this provision, then in addition
to all other remedies Employer may have, Employer shall be entitled to
reimbursement from Executive for any benefits or compensation paid to Executive
under this Agreement on and after the date that Executive first breached this
provision.

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                  5.3      General Responsibilities. Executive will be subject
to Employee's general employment policies and procedures which are described
from time to time in Employer's employee handbook which has been made available
to Executive. Employer may change or terminate the availability of any of the
benefits or responsibilities contained in such employee manual at any time or
from time to time in its sole discretion.

                                   ARTICLE VI

                               GENERAL PROVISIONS

                  6.1      Entire Agreement. This Agreement, the Employee
Invention and Proprietary Information Agreement, and the Non-Qualified Stock
Option Agreement contain the entire understanding and sole and entire agreement
between the parties with respect to the subject matter hereof and supersedes any
and all prior agreements, negotiations and discussions between the parties
hereto with respect to the subject matter covered hereby. Each party to this
Agreement acknowledges that no representations, inducements, promises or
agreements, oral or otherwise, have been made by any party, or anyone acting on
behalf of any party, which are not embodied herein, and that no other agreement,
statement or promise not contained in this Agreement shall be valid or binding.
This Agreement may not be modified or amended by oral agreement, but rather only
by an agreement in writing signed by Executive and the Chief Executive Officer
of Employer which specifically states the intent of the parties to amend this
Agreement.

                  6.2      Assignment and Binding Effect. Neither this Agreement
nor the rights or obligations hereunder shall be assignable by Executive.
Employer may assign this Agreement to any successor of Employer, and upon such
assignment any such successor shall be deemed substituted for Employer upon the
terms and subject to the conditions hereof.

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                  6.3      Dispute Resolution. Any controversy or claim arising
out of or relating to this Agreement, or the breach thereof, that cannot be
resolved between the parties in a timely manner shall be resolved through final
and binding arbitration in San Diego, California in accordance with the
then-existing commercial arbitration rules (the "Rules") of the American
Arbitration Association ("AAA"), and judgement upon the award rendered by the
arbitrators may be entered in any court having competent jurisdiction thereof;
provided, however, that the law applicable to any controversy shall be the law
of the State of California, regardless of its or any other jurisdiction's choice
of law principles. Notwithstanding the above, nothing herein shall require
Employer to arbitrate any claim involving alleged breaches by Executive of his
duties to maintain the confidentiality of Employer's confidential or proprietary
information, including trade secrets, or to disclose and assign inventions to
Employer. Such claims may be the subject of a court action seeking legal or
equitable relief.

                  6.4      No Waiver. No waiver of any term, provision or
condition of this Agreement, whether by conduct or otherwise, in any one or more
instances shall be deemed or be construed as a further or continuing waiver of
any such term, provision or condition, or as a waiver of any other term,
provision or condition of this Agreement.

                  6.5      Governing Law; Rules of Construction. This Agreement
has been negotiated and executed in, and shall be governed by and construed in
accordance with the laws of, the State of California. Captions of the several
Articles and Sections of this Agreement are for convenience of reference only,
and shall not be considered or referred to in resolving questions of
interpretation with respect to this Agreement.

                  6.6      Notices. Any notice, request, demand or other
communication required or permitted hereunder shall be deemed to be properly
given when personally served in writing, or

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when deposited in the United States mail, postage pre-paid, addressed to
Employer or Executive at his last-known address. Each party may change its
address by written notice in accordance with this Section.

                  Address for Employer:

                           Stratagene Holding Corporation
                           11011 North Torrey Pines Road
                           La Jolla, California  92037
                           Attention: Joseph A. Sorge, M.D.

                  Address for Executive:

                           Nicolas H. Roelofs, Ph.D.
                           [Intentionally Omitted]
                           [Intentionally Omitted]

                  6.7      Severability. The provisions of this Agreement are
severable. If any provision of this Agreement shall be held to be invalid or
otherwise unenforceable, in whole or in part, the remainder of the provisions or
enforceable parts hereof shall not be affected thereby and shall be enforced to
the fullest extent permitted by law.

                  6.8      Multiple Counterparts. This Agreement may be executed
in one or more counterparts, each of which shall be deemed an original, but all
of which together shall constitute one and the same instrument.

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                  IN WITNESS WHEREOF, this Agreement has been executed and
delivered by the parties hereto as of the date first above written.

                                      EMPLOYER:

                                      STRATAGENE HOLDING CORPORATION.

                                      By:        /s/ JOSEPH A SORGE, M.D.
                                          --------------------------------------
                                      Name:  Joseph A. Sorge, M.D.
                                      Title: Chief Executive Officer

                                      EXECUTIVE:

                                             /s/ NICOLAS H. ROELOFS, PH.D.
                                      ------------------------------------------
                                               Nicolas H. Roelofs, Ph.D.

                                      Address: [Intentionally Omitted]
                                               [Intentionally Omitted]

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                                    EXHIBIT A

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                                    EXHIBIT B

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