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                                                                   Exhibit 10(q)


                              EMPLOYMENT AGREEMENT

     This AGREEMENT ("Agreement") effective as of _______________ is entered
into by and between the Sigma-Aldrich Corporation, a Delaware corporation
("Company") and _______________ ("Executive"), an individual.

                                 WITNESS THAT:

WHEREAS, Executive has been effective in his or her service to the Company and
its subsidiaries, and the Company recognizes the valuable services that
Executive has rendered and desires to be assured that Executive will continue
his or her active participation in the business of the Company; and

WHEREAS, Executive is willing to serve the Company and its subsidiaries but
desires assurance that in the event of any change in control of the Company that
Executive will continue to have the opportunity of employment as provided under
the terms of this Agreement;

     NOW, THEREFORE, in consideration of the promises and the mutual agreements
contained herein, Company and Executive hereby agree as follows:

1. Term. This Agreement shall commence on the date hereof and end on the last
day of April, 2005 unless terminated or extended prior to that date. On April
30, 2003 and the last day of April every year thereafter, this Agreement shall
be automatically extended one additional year unless, prior to such last day of
April, the Company shall have delivered to Executive or Executive shall have
delivered to the Company written notice that the Executive's employment
hereunder will not be so extended. Anything in this Paragraph 1 to the contrary
notwithstanding, Executive and Company shall each have the right to terminate
this Agreement at any time by a 60 day written notice to the other; provided,
however, that such 60 day termination right shall no longer be available to the
Company after a change in control of the Company.

2. Compensation. Executive's cash compensation shall be reviewed and set
annually either by the Board of Directors of the Company or by the Compensation
Committee of the Board of Directors. Such cash compensation shall be paid either
by the Company or by a subsidiary of the Company designated by the Board of
Directors of the Company. The salary portion of cash compensation shall be paid
to Executive in

                                       (1)

<PAGE>

twenty-four equal installments during the year. The cash bonus portion, if any,
shall be paid no later than 90 days following the end of the year in which it is
earned. Subsequent to a change in control of the Company, Executive's total cash
compensation (salary plus bonus) may not be reduced below the level in effect
immediately prior to the change in control.

3. Duties. Executive shall perform the duties assigned from time to time by the
Board of Directors of the Company.

4. Death. The Company's obligations under this Agreement shall terminate on the
last day of the month in which Executive's death occurs. Any payments then due
to Executive shall be made to Executive's estate. Such payments shall include
the cash salary payment for the month in which Executive's death occurred (if
not previously made) and a cash bonus payment in accordance with the Company's
cash bonus program.

5. Executive Departure. If either the Company or Executive believes, after a
change in control of the Company, that Executive is not able, or will not in the
future be able, to perform the assigned duties hereunder, Company or Executive,
as the case may be, shall so notify the other whereupon Executive's employment
shall cease without jeopardizing any rights to compensation under the terms of
Paragraph 2 for the remaining term of the Agreement. The compensation paid
Executive after cessation of employment pursuant to this Paragraph 5 shall be
considered severance pay.

6. Noncompete and Secrets. Anything in this Agreement to the contrary
notwithstanding, Executive's breach of the Sigma-Aldrich Company Employment
Agreement and Supplement to Agreement, which is expressly made a part hereof and
is appended hereto as Exhibit 1, shall relieve the Company of its obligations
under this Agreement except for the payment of any compensation due Executive to
the date of such breach.

7. For purposes of this Agreement, a "change in control" of the Company shall be
deemed to have occurred if:

     (a) Individuals who constitute the incumbent board cease for any reason to
constitute at least a majority of the Board of Directors. The "incumbent board"
means the group of directors consisting of (i) those individuals who, as of the
effective date of this Agreement, constituted the Board of Directors and (ii)
any individuals who become directors subsequent to such effective date whose
appointment,

                                      (2)

<PAGE>

election or nomination for election by the shareholders of the Company was
approved by a vote of at least a majority of the directors then comprising the
incumbent board, excluding, however, members of the incumbent board who are no
longer serving as directors. The incumbent board shall exclude any individual
whose initial assumption of office occurred (i) as a result of an actual or
threatened election contest with respect to the election or removal of directors
or other actual or threatened solicitation of proxies or consents by or on
behalf of a person (other than a solicitation of proxies by the incumbent board)
or (ii) with the approval of the incumbent board but by reason of any agreement
intended to avoid or settle a proxy contest.

     (b) More than 25% of (i) the combined voting power of the then outstanding
voting securities of the Company entitled to vote generally in the election of
directors ("outstanding Company voting securities") or (ii) the then outstanding
shares of the Company's common stock ("outstanding Company common stock") is
directly or indirectly acquired or beneficially owned (as defined in Rule 13d-3
under the Securities Exchange Act of 1934 (the "Exchange Act"), or any successor
rule thereto) by any individual, entity or group (within the meaning of Section
13(d)(3) or 14(d)(2) of the Exchange Act), provided, however, that the following
acquisitions and beneficial ownership shall not constitute changes in control
pursuant to this subsection (b):

          (A) any acquisition or beneficial ownership by the Company or a
     subsidiary, or

          (B) any acquisition or beneficial ownership by any employee benefit
     plan (or related trust) sponsored or maintained by the Company or one of
     more of its subsidiaries.

     (c) Consummation of a reorganization, merger, share exchange or
consolidation (a "business combination"), unless in each case following such
business combination:

          (i) all or substantially all of the individuals and entities who were
     the beneficial owners, respectively, of the outstanding Company common
     stock and outstanding Company voting securities immediately prior to such
     business combination beneficially own, directly or indirectly, more than
     50% of, respectively, the then outstanding shares of common stock and the
     combined voting power of the then outstanding voting securities entitled to
     vote generally in the election of directors or other governing body, as the
     case may be, of the entity resulting from such business

                                      (3)

<PAGE>

     combination (including, without limitation, an entity that as a result of
     such transaction owns the Company through one or more subsidiaries);

          (ii) no individual, entity or group (excluding any employee benefit
     plan (or related trust) of the Company or such corporation resulting from
     such business combination) beneficially owns, directly or indirectly, more
     than 25% of, respectively, the then outstanding shares of common stock of
     the corporation resulting from such business combination or the combined
     voting power of the then outstanding voting securities of such corporation
     entitled to vote generally in the election of directors or other governing
     body of the entity resulting from such business combination, except to the
     extent that such individual, entity or group owned more than 25% of the
     outstanding Company common stock or outstanding Company voting securities
     prior to the business combination; and

          (iii) at least a majority of the members of the board of directors or
     other governing body of the entity resulting from such business combination
     were members of the incumbent board at the time of the execution of the
     initial agreement, or of the action of the Board of Directors, approving
     such business combination.

     (d) The Company shall sell or otherwise dispose of all or substantially all
of the assets of the Company (in one transaction or a series of transactions).

     (e) The shareholders of the Company shall approve a plan liquidate or
dissolve the Company, and the Company shall commence such liquidation or
dissolution.

8. Offset. Subsequent to a change in control and a cessation of Executive's
employment with the Company or any subsidiary, to the extent that Executive
shall receive compensation for personal services from employment other than with
Company during the term of this Agreement, the amounts so earned shall be offset
against the amounts due under this Agreement and shall serve to reduce such
amounts due.

9. Modification. This Agreement may be modified only upon the written consent of
the Company and Executive.

                                       (4)

<PAGE>

10. Legal Expenses. In the event that Executive institutes any legal action to
enforce the rights under, or to recover damages for breach of this Agreement,
Executive, if the prevailing party, shall be entitled to recover from the
Company any reasonable expenses actually incurred for attorney's fees and
disbursements.

     IN WITNESS WHEREOF, the parties have executed this Agreement on the
specified date indicated.


COMPANY:                                 EXECUTIVE:


By:                                      By:
   -------------------------------          --------------------------------
      Name:                                    Name:
           -----------------------                  ------------------------
      Title:                                   Title:
            ----------------------                   -----------------------

Date:
     -----------------------------

                                       (5)

<PAGE>
                                                                       Exhibit 1

                [LOGO OF SIGMA-ALDRICH CORPORATION APPEARS HERE]

                  AGREEMENT between SIGMA-ALDRICH CORPORATION and


                  -----------------------------------------------


     In consideration of the compensation and other benefits of my employment or
continued employment by Sigma-Aldrich Corporation (the Company) and of other
valuable consideration, I agree as follows:

CONFIDENTIAL INFORMATION

     I recognize that the Company is engaged in the business of research,
development, manufacture and sale of chemicals, chemical products and allied
activities, which business requires for its successful operation the fullest
security of its Confidential Information of which I will acquire knowledge
during the course of my employment.

     As used in this agreement, "Confidential Information" means all technical
and business information of the Company, or which is learned or acquired by the
Company from others with whom the Company has a business relationship in which,
and as a result of which, similar information is revealed to the Company,
whether patentable or not, which is of a confidential, trade secret and/or
proprietary character and which is either developed by me (alone or with others)
or to which I shall have had access during my employment. Confidential
Information shall include all data, designs, plans, notes, memoranda, work
sheets, formulas, processes, patents, customer and supplier lists.

     I shall use my best efforts and diligence both during and after my
employment with the Company, regardless of how, when or why my employment ends
to protect the confidential, trade secret and/or proprietary character of all
Confidential Information. I shall not, directly or indirectly, use (for myself
or another) or disclose any Confidential Information, for so long as it shall
remain proprietary or protectible as confidential or trade secret information,
except as may be necessary for the performance of my duties for the Company.

     I shall promptly deliver to the Company, at the termination of my
employment or at any other time at the Company's request, without retaining any
copies, all documents and other material in my possession relating, directly or
indirectly, to any Confidential Information.

     Each of my obligations in this section shall also apply to the
confidential, trade secret and proprietary information learned or acquired by me
during my employment from others with whom the Company has a business
relationship.

COMPETITIVE ACTIVITY

     I shall not, directly or indirectly (whether as owner, partner, consultant,
employee or otherwise), at any time during the period of my employment by the
Company and for a period of two years following termination of my employment,
regardless of how, when or why my employment ends, engage in or contribute my
knowledge to or invest in any business that is engaged in any work or activity
that involves a product, process, service or development which is then
competitive with and the same as or similar to a product, process, service or
development on which I worked or with respect to which I had access to
Confidential Information while with the Company. However, I shall be permitted
to engage in such proposed work or activity, and the Company shall furnish me a
written consent to that effect signed by an officer, if I shall have furnished
to the Company clear and convincing written evidence, including assurances from
me and my new employer, that the fulfillment of my duties in such proposed work
or activity would not cause me to disclose, base judgments upon, or use any
Confidential Information, including information relating to the identity of or
products supplied to or purchased from the customers or suppliers of the
Company.

     Following expiration of said two-year period, I shall continue to be
obligated under the "Confidential

                                      A-1

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Information" section of this Agreement not to use or to disclose Confidential
Information so long as it shall remain proprietary or protectible as
confidential or trade secret information.

     Following termination of my employment for any reason, I agree to advise
the Company of my new employer, work location and job responsibilities within
ten days after accepting new employment. I further agree to keep the Company so
advised of any change in my employment for two years following termination of my
employment with the Company.

     I understand that it is not the intention of this Agreement to prevent me
from earning a livelihood, and I agree nothing in this Agreement would prevent
me from earning a livelihood utilizing my general purchasing, sales,
professional or technical skills in any of the hospitals, businesses, research
or manufacturing facilities of companies which are not directly or indirectly in
competition with the Company.

     I agree that while employed by the Company and for a period of two (2)
years following termination of employment, regardless of how, when or why my
employment ends, I shall not in any manner or in any capacity, directly or
indirectly, for myself or any other person or entity, actually or attempt: (a)
to solicit any customer or potential customer of the Company for the purpose of
selling any products competitive with products sold by the Company, or otherwise
interfere with or take away any customer or potential customer of the Company or
the business of any such customer or potential customer; or (b) to interfere
with the Company's relationship with any customer or supplier of the Company.

     The term "customer" shall mean any person or entity to whom the Company has
sold any products (a) in the case of on-going employment, during the twenty-four
(24) calendar months immediately preceding any dispute under this paragraph and,
(b) in the case of employment having ended, the twenty-four (24) calendar months
preceding termination of employment. The term "potential customer" shall mean
any person or entity who, during the applicable twenty-four (24) month period
described above has (a) been involved in discussions or negotiations with the
Company for products sold by the Company; (b) initiated contact with the Company
in order to obtain information regarding products sold by the Company; (c) been
the subject of repeated personal contacts by me and/or any other Company
employee for purposes of soliciting business for the Company; or (d) been the
subject of the Company's efforts to gather, learn or evaluate information which
may help the Company obtain any future order from such person or entity.

IDEAS, INVENTIONS, DISCOVERIES

     I shall promptly disclose to the Company all ideas, inventions or
discoveries, whether or not patentable, which I may conceive or make (alone or
with others) during my employment, whether or not during working hours, and
which, directly or indirectly,
     (a) relate to matters within the scope of my duties or field of
         responsibility during my employment with the Company; or
     (b) are based on my knowledge of the actual or anticipated business or
         interest of the Company; or
     (c) are aided by the use of time, materials, facilities or information of
         the Company.

     I hereby assign to the Company or its designee, without further
compensation, all of the right, title and interest in all such ideas, inventions
or discoveries in all countries of the world.

     Without further compensation but at the Company's expense, I shall give all
testimony and execute all patent applications, rights of priority, assignments
and other documents and in general do all lawful things requested of me by the
Company to enable the Company to obtain, maintain and enforce protection of such
ideas, inventions and discoveries for and in the name of the Company or its
designee (as the case may be) in all countries of the world. However, should I
render any of these services during a two-year period following termination of
my employment, I shall be compensated at a rate per hour equal to the basic
salary I received from the Company at the time of termination and shall be
reimbursed for reasonable out-of-pocket expenses incurred in rendering the
services.

GENERAL

     If I am employed by an affiliate of the Company and have not entered into a
superseding agreement with my new employer covering the subject matter of this
Agreement, then this Agreement shall continue in effect and my new employer
shall be termed "the Company" for all purposes hereunder and shall have the
right to enforce this Agreement as my employer. In the event of any subsequent
employment by the Company or any other affiliate, my new employer shall succeed
to all rights under this Agreement so long as such employer shall be an
affiliate of the Company and so long as this Agreement has not been superseded.

                                      A-2

<PAGE>

     As used in this Agreement, an "affiliate" of the Company shall mean any
parent or subsidiary of the Company, and company owned or controlled by any
parent of the Company as well as any subsidiary of such companies and any
company or corporation with which the Company has a contractual or ongoing
business relationship which requires the Company and such other company or
corporation to agree to noncompetition or non-disclosure covenants similar to or
the same as those contained herein.

     The Company and I shall have the right to terminate my employment at any
time by giving at least 14 days written notice to the other party; provided,
however, the Company may terminate my employment without notice at any time for
any cause deemed by it to be a breach of my employment duties or of any of my
obligations under this Agreement. The Company, at its option, may elect to pay
my salary for the notice period instead of continuing my active employment
during that period.

     I hereby acknowledge that damages for the violation of the provisions
contained in this Agreement will not give full and sufficient relief to the
Company, and I agree that in the event of any violation of any of said
provisions the Company shall be entitled to injunctive relief against violation
thereof, in addition to any other rights it may have by reason of said
violation.

     This Agreement shall be interpreted under the laws of the State of
Missouri, St. Louis County Circuit Court or the U.S. District Court for the
Eastern District of Missouri as the exclusive Forum to resolve any dispute. If
any provision of this Agreement is held invalid in any respect, it shall not
affect the validity of any other provision of this Agreement. If any provision
of this Agreement is held to be unreasonable as to time, scope or otherwise, it
shall be construed by limiting and reducing it so as to be enforceable under
then applicable law.

This Agreement is signed in duplicate, as of the __ day of ______________, 2001.

SIGMA-ALDRICH CORPORATION


By
  -----------------------------------------

Terry Colvin           V.P. Human Resources
-------------------------------------------
Typed Name and Title


-------------------------------------------
Signature of Employee


-------------------------------------------
Typed Name of Employee

                                      A-3

<PAGE>


                             SIGMA CHEMICAL COMPANY
                             Supplement to Agreement

In addition to the AGREEMENT, which Sigma Chemical Company (the Company) and I
have signed, the conditions of my employment with the Company include the
following:

Date of Employment                           Salary
                   -----------------------          ----------------------------
Position                                     Department
         ---------------------------------              ------------------------

PAY PERIOD - Semi-Monthly.

VACATION - The vacation year begins on April 1 and ends on March 31. I will
receive .83 days of vacation for each full month of service until I reach April
1 following completion of one year of service. I may use this time in full-day
and half-day increments. Upon completion of the specified number of years of
service, I will be entitled to the following vacations:

 1 year: 2 weeks    5 years: 3 weeks    15 years: 4 weeks    25 years: 5 weeks

In addition, upon completion of the anniversary years of 25, 30, 40 and 45 years
of service, employees receive an additional bonus week of vacation for a total
of 6 weeks.

In order to be eligible for any unused vacation pay on termination of
employment, I must give _____ days written notice.

PAID HOLIDAYS - New Year's Day, Memorial Day, July 4, Labor Day, Thanksgiving
                Day, Friday after Thanksgiving and Christmas Day.

PERSONAL CHOICE PAID HOLIDAYS - I may take one Personal Choice Holiday (PCH) as
of the following dates:

--------------------------------------------------------------------------------
Then beginning in _____, I may take four Personal Choice Holidays during each
calendar year.


MAJOR MEDICAL INSURANCE - I will be eligible to participate in a Major Medical
Insurance Program for such expenses as hospital care, surgery, in-hospital
doctor visits, diagnostic services, and certain out-patient and emergency care,
beginning 30 days after date of employment. (Please check with a benefits
coordinator in reference to pre-existing conditions and related benefit
limitations.) Dependent coverage is available.

LIFE INSURANCE - I will be covered by a Company-paid Life Insurance Program
beginning 30 days after date of employment. The value of the policy is equal to
one and one-half of my annual salary. In addition to Life Insurance, the Program
provides Accidental Death and Dismemberment Insurance equal to the Life
Insurance coverage.

DISABILITY INSURANCE - I will be covered by a Company-paid Disability Insurance
Program beginning 6 months after date of employment with benefits of two-thirds
of my salary.

DENTAL INSURANCE - I will be eligible to participate in a Dental Insurance
Program beginning 30 days after date of employment.

RETIREMENT - A Company-paid Retirement Plan is in addition to Social Security
benefits.

TUTITION REIMBURSEMENT - After 6 months of employment, regular full-time
employees can be reimbursed for up to $2,500 of tuition expense annually for job
related courses or courses taken in pursuit of a degree that would prepare the
employee to advance within the Company.

I will receive a performance evaluation at intervals during the first six months
of my employment.

I will devote my full-time and effort to the conscientious performance of my
duties and while employed by the Company, will refrain from engaging, directly
or indirectly, in any other business.

Sigma Chemical Company is an Equal Opportunity Employer and will not
discriminate against any employee on the basis of age, race, color, religion,
sex, national origin or handicap.

I have received the Employee Handbook that explains what I can expect of the
Company and what the Company expects of me.

SIGMA CHEMICAL COMPANY

By
   -----------------------------------    --------------------------------------
Human Resources                           Signature of Employee        Date

--------------------------------------    --------------------------------------
Typed Name and Title                      Typed Name of Employee

                                      A-4