EXHIBIT 10.19


                          MOLECULAR DEVICES CORPORATION


                             KEY EMPLOYEE AGREEMENT
                                       for
                                JOSEPH D. KEEGAN


         This Employment Agreement  ("Agreement") is entered into as of the 11th
day of March, 1998, by and between Joseph D. Keegan  ("Executive") and Molecular
Devices Corporation, a Delaware corporation (the "Company").

         Whereas,  the Company desires to employ  Executive to provide  personal
services  to  the  Company,   and  wishes  to  provide  Executive  with  certain
compensation and benefits in return for his services; and

         Whereas,  Executive  wishes to be  employed  by the Company and provide
personal  services  to the  Company  in  return  for  certain  compensation  and
benefits;

         Now,  Therefore,  in consideration of the mutual promises and covenants
contained  herein,  it is hereby  agreed by and between  the  parties  hereto as
follows:

         1.       Employment by the Company.

                  1.1 Subject to terms set forth herein,  the Company  agrees to
employ  Executive  in the  position of  President  and Chief  Executive  Officer
("CEO") of the Company and Executive hereby accepts such employment effective as
of March 30, 1998. During the term of his employment with the Company, Executive
will devote his best  efforts and  substantially  all of his  business  time and
attention  (except  for  vacation  periods as set forth  herein  and  reasonable
periods of illness or other  incapacities  permitted  by the  Company's  general
employment policies) to the business of the Company.

                  1.2 Executive  shall serve in an executive  capacity and shall
perform such duties as are  customarily  associated with his then current title,
consistent with the Bylaws of the Company and as required by the Company's Board
of Directors (the "Board").

                  1.3 The employment relationship between the parties shall also
be governed by the general  employment  policies  and  practices of the Company,
including  those  relating  to  protection  of   confidential   information  and
assignment of inventions,  except that when the terms of this  Agreement  differ
from or are in  conflict  with the  Company's  general  employment  policies  or
practices, this Agreement shall control. In addition, as an executive officer of
the Company  Executive  will be covered by the Company's  directors and officers
liability  insurance  coverage,  as in effect from time to time,  as well as the
Company's bylaw  indemnification  and indemnity agreement for executive officers
and directors.

         2.       Board of Directors.


<PAGE>


                  2.1 Board of Directors. The Company shall use its best efforts
to elect  Executive to the Board for so long as Executive  holds the position of
President and Chief Executive Officer of the Company.  Executive agrees to serve
as a director if elected by the shareholders and the Board, as the case may be.

         3.       Compensation.

                  3.1  Salary.  Executive  shall  receive  for  services  to  be
rendered  hereunder an annualized base salary of $280,000,  payable according to
the Company's regular payroll schedule.

                  3.2  Signing  Bonus.  Upon his first  performance  of services
under this  Agreement,  Executive  shall receive a one time payment of $150,000,
minus  standard  payroll  withholdings  and  deductions  ("Signing  Bonus").  If
Executive  voluntarily  terminates his employment  with Company within his first
year of employment,  Executive shall repay the gross amount of the Signing Bonus
to the Company.

                  3.3  Performance  Bonus.  Executive  will  be  eligible  for a
discretionary  performance  bonus of up to 50% of base salary,  earned under the
following  conditions,  if Executive achieves the goals established in agreement
with the Board. The Board shall determine,  in its sole discretion,  whether any
or all of the goals have been achieved and conditions  have been met, and if so,
the amount of the bonus.

                           (a) Company  Corporate  Financial  Goals. The Company
must meet or exceed its planned profit objectives for the bonus year; and

                           (b)   Executive's    Performance.    Executive   must
demonstrate  performance  equal to or above that  required to meet the  ordinary
expectations  of his job  position,  as  determined  by the  Board  in its  sole
discretion; and

                           (c)  Achievement  of Goals.  Executive  shall achieve
each of the goals agreed upon with the Board. Goals will be set in the following
areas: (1) product development schedule; (2) product introduction schedule; and

                           (d)  Active  Employment.  Executive  must  remain  an
active employee through the end of the bonus year.  Executive forfeits any bonus
for which he would otherwise be eligible,  if his employment  terminates for any
reason before the end of the bonus year. No prorated bonus can be earned.

                  3.4 Standard Company Benefits.  Executive shall be entitled to
all rights and benefits for which he is eligible  under the terms and conditions
of the standard  Company  benefits and  compensation  practices  which may be in
effect from time to time and provided by the Company to its employees generally.

                  3.5 Car Allowance.  The Company will pay Executive, in lieu of
providing a  Company-leased  car,  an  allowance  of $1,000 per month,  to cover
transportation expenses in the performance of his job duties.

                                       2
<PAGE>


                  3.6  Administrative  Expenses.  The Company will pay Executive
for administrative expenses, such as tax preparation, which Executive incurs, up
to a maximum of $5,000 per year.

                  3.7 Relocation  Expenses.  Executive  will receive  relocation
expenses to move his household  from New York to  California  provided that such
relocation  occurs prior to December 31, 1998. The Company will pay the lower of
two submitted  bids,  pursuant to the Relocation  Agreement  attached  hereto as
Exhibit A.

                  3.8 Commuting Expenses.  The Company will provide Executive or
his  immediate  family with one round trip per week between  California  and New
York, for up to six months after the start of Executive's employment.

                  3.9  Taxation.  Any  amount  received  by  the  Executive  for
administrative  expenses,  car  allowance,   relocation  expenses  or  commuting
expenses that is required to be so treated will be treated as taxable income and
reflected on the Company's Form W-2 report.

                  3.10  Compensation  Review.  The Board  will  annually  review
Executive's  salary,  performance  bonus,  and incentive stock options to ensure
that they are commensurate  with work performed.  In addition,  the Company will
annually  review and mutually  establish  with Executive the goals to be used in
evaluating Executive's performance bonus.

         4.       Stock.

                  4.1 Stock Options. The Board will grant Executive an option to
purchase one hundred  seventy  thousand  (170,000)  shares of  Molecular  Device
Corporation's  Common Stock under the Company's  Stock Option Plan (the "Plan").
The exercise price of this Stock Option will be the price of the Common Stock on
the date on which Executive begins employment with the Company. The Stock Option
will vest over five years. Thirty four thousand (34,000) shares will vest on the
first  anniversary of Executive's  employment.  Thereafter,  eight thousand five
hundred shares  (8,500) will vest every  quarter.  Vesting ceases if Executive's
employment terminates at any time for any reason, with the following exceptions.
If the Company is merged with or acquired by another  company and  Executive  is
either  demoted or  terminated  without  cause (as defined in Section 7.2 below)
within two years following the merger or  acquisition,  vesting of the remaining
unvested options will accelerate,  such that Executive will be vested in a total
of one hundred seventy thousand (170,000) shares.

                  4.2 Stock Grant.  The Board will grant  Executive an aggregate
of thirty thousand (30,000) shares of Molecular  Device's stock,  subject to SEC
restrictions,  over the next two years.  Three  thousand seven hundred and fifty
(3,750)  shares will be granted  following  the  completion  of each  quarter of
service with the Company in an executive  capacity.  Executive will bear all tax
responsibilities for these grants and will make arrangements with the Company to
ensure payment of taxes. Granting ceases if Executive's employment terminates at
any time for any reason, with the following 

                                       3
<PAGE>


exceptions.  If the Company is merged  with or  acquired by another  company and
Executive is either  demoted or terminated  without cause (as defined in Section
7.2 below) within two years following the merger or acquisition, granting of the
remaining  ungranted stock will accelerate such that Executive will be granted a
total of thirty thousand (30,000) shares.

         5.       Proprietary Information Obligations.

                  5.1  Agreement.  Executive  agrees to execute and abide by the
Proprietary Information and Inventions Agreement attached hereto as Exhibit B.

                  5.2  Remedies.   Executive's   duties  under  the  Proprietary
Information and Inventions Agreement shall survive termination of his employment
with the Company.  Executive acknowledges that a remedy at law for any breach or
threatened  breach by him of the provisions of the  Proprietary  Information and
Inventions  Agreement  would be  inadequate,  and he  therefore  agrees that the
Company  shall be  entitled to  injunctive  relief in case of any such breach or
threatened breach.

         6.       Outside Activities.

                  6.1 Except  with the prior  written  consent of the  Company's
Board of  Directors,  Executive  will  not  during  the  term of this  Agreement
undertake or engage in any other employment,  occupation or business enterprise,
other than ones in which Executive is a passive  investor within the limitations
set forth in Section 6.3 below. Executive may engage in civic and not-for-profit
activities  so long as such  activities  do not  materially  interfere  with the
performance of his duties hereunder.

                  6.2 Except as permitted by Section 6.3,  Executive  agrees not
to acquire,  assume or participate  in,  directly or  indirectly,  any position,
investment  or  interest  known  by him to be  adverse  or  antagonistic  to the
Company, its business or prospects, financial or otherwise.

                  6.3 During the term of his  employment by the Company,  except
on behalf of the Company, Executive will not directly or indirectly,  whether as
an   officer,   director,   stockholder,    partner,   proprietor,    associate,
representative,  consultant,  or in any 

                                       4
<PAGE>


capacity whatsoever engage in, become financially  interested in, be employed by
or have any  business  connection  with any  other  person,  corporation,  firm,
partnership  or other  entity  whatsoever  which  were  known by him to  compete
directly with the Company, throughout the world, in any line of business engaged
in (or  planned  to be  engaged  in) by the  Company;  provided,  however,  that
anything  above  to the  contrary  notwithstanding,  he may  own,  as a  passive
investor,  securities  of any  competitor  corporation,  so long  as his  direct
holdings in any one such corporation shall not in the aggregate  constitute more
than 1% of the voting stock of such corporation.

         7.       Termination Of Employment.

                  7.1      Termination Without Cause Or With Good Reason.

                           (a) The  Company  shall  have the right to  terminate
Executive's employment with the Company at any time without cause.

                           (b) In the event Executive's employment is terminated
without cause, or in the event Executive resigns for Good Reason (defined as the
Company's  having  appointed  another person as Chief  Executive  Officer),  the
Company shall provide  Executive with the following:  (i) a one-year  consulting
agreement  as  described  in  Sections  8 and 9  below;  and  (ii)  outplacement
services.

                  7.2      Termination for Cause.

                           (a) The  Company  shall  have the right to  terminate
Executive's employment with the Company at any time for cause.

                           (b) "Cause" for  termination  shall be  determined by
the  Company  based on the  Board's  reasonable  belief  that one or more of the
following has occurred:  (a) Executive's  indictment or conviction of any felony
or of any crime involving dishonesty; (b) Executive's participation in any fraud
against the Company; (c) breach of Executive's duties to the Company,  including
persistent  unsatisfactory  performance of job duties, provided that the Company
has provided  advance  written notice to Executive for at least thirty (30) days
and Executive has not cured such breach to the  satisfaction of the Board within
said 30-day period;  (d) Executive's  intentional  damage to any property of the
Company;  or (e)  conduct by  Executive  which in the good faith and  reasonable
determination of the Board demonstrates gross unfitness to serve,  provided that
the Company has provided advance written notice to Executive for at least thirty
(30) days and  Executive  has not cured such breach to the  satisfaction  of the
Board within said 30-day period.

                           (c) In the event Executive's employment is terminated
at any time with cause, he will not be entitled to severance pay, pay in lieu of
notice or any other such compensation.

                  7.3      Voluntary or Mutual Termination.

                           (a)   Executive   may   voluntarily   terminate   his
employment  with the Company at any time,  after  which no further  compensation
will be paid to Executive.

                                       5
<PAGE>

                           (b) In the event Executive voluntarily terminates his
employment,  he will not be entitled to severance  pay, pay in lieu of notice or
any other such compensation.

         8.       Post-Employment Consultation.

                  Upon  the  termination  of  Executive's  employment  with  the
Company  pursuant to Section  7.1(b),  the Company  shall retain  Executive as a
consultant to be available to render consulting  services in Executive's area of
expertise or special  competence for one year ("Consulting  Period"),  for up to
ten (10) hours each month, for which the Company shall pay Executive Executive's
monthly base salary, whether or not Executive shall be called upon to render any
services in any such month.  During the  Consulting  Period,  Executive's  stock
options and stock grant will  continue to vest at the rate in effect at the time
of  termination.  Vesting of stock options and the stock grant will cease at the
end of the Consulting  Period.  Any  out-of-pocket  expenses  which  Executive's
consulting  activities  for the Company may require will be  reimbursed  against
receipts and vouchers  therefor in  accordance  with the  Company's  policies in
force from time to time.

         9.       Post-Employment Activities.

                  If the Company retains  Executive as a consultant  pursuant to
Section 8 above,  then the  following  restrictions  shall  apply so long as the
Company retains Executive as a consultant:

                  9.1  Absent  the  Company's   prior   written   approval  upon
instructions  of  its  Board  of  Directors,  Executive  will  not  directly  or
indirectly engage in activities (similar or reasonably related to those in which
Executive  shall  have  engaged  hereunder  during  the  two  years  immediately
preceding the termination of Executive's employment with the Company) nor render
services  (similar or  reasonably  related to those which  Executive  shall have
rendered hereunder during such two years) in either case to any firm or business
organization  which  directly  competes with the Company in any line of business
engaged in (or planed to be engaged in) by the Company,  whether now existing or
hereafter established,  nor shall Executive engage in such activities nor render
such services to any other person or entity  engaged or about to become  engaged
in  such  activities  to,  for  or on  behalf  of  any  such  firm  or  business
organization,  nor  shall  Executive  entice,  induce  or  encourage  any of the
company's  other  employees  to engage in any  activity  which,  were it done by
Executive,  would violate any provision of the Proprietary Information Agreement
or this Section 9.

                  9.2 The Company upon instruction of its Board of Directors may
give  Executive  written  approval(s)  to engage  personally  in any activity or
render  services  referred  to in Section 9.1 if it secures  written  assurances
(satisfactory  to the  Company  and its  counsel)  from  Executive  and from the
prospective  employer(s)  that  the  integrity  of the  Proprietary  Information
Agreement will not in any way be jeopardized  by such  activities,  provided the
burden of so establishing  the foregoing to the  satisfaction of the Company and
said counsel shall be upon Executive and his prospective employer(s).

                                       6
<PAGE>

                  9.3 The  provisions  of  Section  6.3 shall be  applicable  to
Executive and Executive  shall comply  therewith.  As applied to such consulting
period,  the term "any line of business engaged in (or planned to be engaged in)
by the  Company",  as used in  Section  6.3,  shall be applied as at the date of
termination of Executive's employment.

         10.      Noninterference.

                  For two (2) years  immediately  following the  termination  of
employment hereunder, Executive agrees not to interfere with the business of the
Company by:

                  (a) soliciting,  attempting to solicit, inducing, or otherwise
causing any employee of the Company to terminate his or her  employment in order
to  become an  employee,  consultant  or  independent  contractor  to or for any
competitor of the Company; or

                  (b)  directly or  indirectly  soliciting  the  business of any
customer of the Company,  for products or services  competitive  with  Molecular
Devices  products or services,  which customer at the time of termination or one
year immediately prior thereto was listed on the Company's customer list.

         11.      General Provisions.

                  11.1  Notices.  Any  notices  provided  hereunder  must  be in
writing and shall be deemed  effective  upon the  earlier of  personal  delivery
(including  personal  delivery  by fax) or the third day after  mailing by first
class mail,  to the Company at its primary  office  location and to Executive at
his address as listed on the Company payroll.

                  11.2 Severability.  Whenever possible,  each provision of this
Agreement  will be interpreted in such manner as to be effective and valid under
applicable  law, but if any  provision of this  Agreement is held to be invalid,
illegal or  unenforceable in any respect under any applicable law or rule in any
jurisdiction,  such invalidity,  illegality or unenforceability  will not affect
any  other  provision  or any other  jurisdiction,  but this  Agreement  will be
reformed,  construed  and  enforced  in such  jurisdiction  as if such  invalid,
illegal or unenforceable provisions had never been contained herein.

                  11.3  Waiver.  If either  party should waive any breach of any
provisions  of this  Agreement,  he or it shall  not  thereby  be deemed to have
waived any preceding or succeeding  breach of the same or any other provision of
this Agreement.

                  11.4  Complete  Agreement.  This  Agreement  and its Exhibits,
constitute the entire agreement  between Executive and the Company and it is the
complete, final, and exclusive embodiment of their agreement with regard to this
subject  matter.  It  is  entered  into  without  reliance  on  any  promise  or
representation  other than those expressly  contained  herein,  and it cannot be
modified or amended except in a writing approved by the Board.

                  11.5 Counterparts.  This Agreement may be executed in separate
counterparts,  any one of which  need not  contain  signatures  of more than one
party,  but all of  which  taken  together  will  constitute  one  and the  same
Agreement.

                                       7
<PAGE>

                  11.6  Headings.  The  headings  of  the  sections  hereof  are
inserted  for  convenience  only and shall not be  deemed to  constitute  a part
hereof nor to affect the meaning thereof.

                  11.7  Successors  and Assigns.  This  Agreement is intended to
bind  and  inure to the  benefit  of and be  enforceable  by  Executive  and the
Company,  and  their  respective  successors,   assigns,  heirs,  executors  and
administrators, except that Executive may not assign any of his duties hereunder
and he may not assign any of his rights hereunder without the written consent of
the Company, which shall not be withheld unreasonably.

                  11.8 Choice of Law. All questions concerning the construction,
validity and interpretation of this Agreement will be governed by the law of the
State of California, without regard to conflict of laws principles.

         In Witness Whereof, the parties have executed this Agreement on the day
and year first above written.

                                           Molecular Devices Corporation


          By:       Andre F. Marion
             ------------------------------


          Date:         3/6/98
                ---------------------------

Accepted and agreed this 11th day of March, 1998.


      /s/ Joseph D. Keegan
---------------------------------
          Joseph D. Keegan

                                       8
<PAGE>

                                    EXHIBIT A

                          MOLECULAR DEVICES CORPORATION

                              RELOCATION AGREEMENT

Effective on March 11, 1998,  I, Joseph D. Keegan  hereby agree to the following
terms and conditions  with respect to all  relocation  costs paid to me or on my
behalf by Molecular  Devices  Corporation in connection  with my relocation from
New York to my new home in California (the "Relocation Costs"):

1.       If I remain a full-time  Molecular  Devices  Corporation  employee  for
         twelve  months from the effective  date stated  above,  I shall have no
         obligation to repay any of the Relocation Costs.

2.       If my employment  terminates within one year from the effective date, I
         agree  to repay to  Molecular  Devices  Corporation  a  portion  of the
         Relocation  Costs,  or other  amounts  paid to  federal  or  state  tax
         agencies as withholding, to be calculated as follows:

                  For each full month of full-time employment, Molecular Devices
                  Corporation  will forgive  1/12 of my  Relocation  Costs.  The
                  remaining  unforgiven  Relocation Costs are due and payable to
                  Molecular Devices on demand.

3.       I  understand  that all  reimbursements  and  allowances  paid to me as
         Relocation Costs,  including amounts withheld as payroll  deductions in
         connection  with my  relocation  must be included as a part of my gross
         income and  therefore  may be subject to tax.  If I am  required  under
         paragraph 2 of this  agreement to repay  Relocation  Costs to Molecular
         Devices  Corporation,  I will repay the entire amount  determined under
         paragraph 2, and amounts withheld as payroll deductions.

4.       I understand that nothing in this agreement  assures me of a continuing
         position with Molecular Devices Corporation,  or in any way changes the
         Molecular   Devices   Corporation's   right   to  end  the   employment
         relationship as it deems necessary.

5.       If I am  obligated  under this  agreement  to repay  Molecular  Devices
         Corporation for Relocation Costs, I hereby authorize  Molecular Devices
         Corporation  to deduct  the entire  amount due from my final  paycheck,
         including from any vacation pay due.

6.       Before  submitting  expenses for  reimbursement as Relocation  Costs, I
         will inform Molecular Devices Corporation whether my spouse is eligible
         for relocation benefits from another employer,  and if so, the terms of
         those benefits. If my spouse is eligible for any of the same relocation
         benefits which the Molecular Devices Corporation has offered me, I will
         only receive  one-half of any such benefits from the Molecular  Devices
         Corporation.

                                       9
<PAGE>



     /s/ Joseph D. Keegan                                      3/11/98
---------------------------------                 ------------------------------
         Joseph D. Keegan                                       Date



<PAGE>


                                    EXHIBIT B
                          MOLECULAR DEVICES CORPORATION

                        EMPLOYEE PROPRIETARY INFORMATION
                            AND INVENTIONS AGREEMENT


         In consideration of my employment or continued  employment by Molecular
Devices Corporation (the "Company"), and the compensation now and hereafter paid
to me, I hereby agree as follows:


1.       Nondisclosure

         1.1 Recognition of Company's Rights; Nondisclosure. At all times during
my employment and thereafter,  I will hold in strictest  confidence and will not
disclose,  use,  lecture  upon  or  publish  any  of the  Company's  Proprietary
Information (defined below),  except as such disclosure,  use or publication may
be required in connection with my work for the Company,  or unless an officer of
the  Company  expressly  authorizes  such in writing.  I will  obtain  Company's
written  approval  before  publishing or submitting for publication any material
(written,  verbal,  or  otherwise)  that  relates to my work at  Company  and/or
incorporates  any  Proprietary  Information.  I hereby assign to the Company any
rights I may have or acquire in such Proprietary  Information and recognize that
all  Proprietary  Information  shall be the sole property of the Company and its
assigns.

         1.2 Proprietary Information.  The term "Proprietary  Information" shall
mean any and all confidential and/or proprietary knowledge,  data or information
of  the  Company.  By way  of  illustration  but  not  limitation,  "Proprietary
Information"  includes  (a)  trade  secrets,   inventions,  mask  works,  ideas,
processes,  formulas,  source and object codes, data,  programs,  other works of
authorship,  know-how,  improvements,  discoveries,  developments,  designs  and
techniques  (hereinafter  collectively  referred  to as  "Inventions");  and (b)
tangible and intangible  information relating to antibodies and other biological
materials, cell lines, samples of assay components,  media and/or cell lines and
procedures  and  formulations  for  producing any such assay  components,  media
and/or  cell  lines,  formulations,   products,  processes,  know-how,  designs,
formulas,   methods,   developmental  or  experimental   work,   clinical  data,
improvements,  discoveries,  plans for  research,  new  products,  marketing and
selling, business plans, budgets and unpublished financial statements, licenses,
prices and costs, suppliers and customers,  and information regarding the skills
and  compensation  of  other  employees  of  the  Company.  Notwithstanding  the
foregoing,  it is  understood  that,  at  all  such  times,  I am  free  to  use
information  which is  generally  known in the trade or  industry,  which is not
gained as result of a breach of this Agreement,  and my own,  skill,  knowledge,
know-how and experience to whatever extent and in whichever way I wish.

         1.3 Third  Party  Information.  I  understand,  in  addition,  that the
Company  has  received  and  in the  future  will  receive  from  third  parties
confidential or proprietary information ("Third Party Information") subject to a
duty on the Company's part to maintain the  confidentiality  of such information
and  to use it  only  for  certain  limited  purposes.  During  the  term  of my
employment and thereafter,  I will hold Third Party Information in the strictest
confidence  and will not disclose to anyone  (other than Company  personnel  who
need to know such  information in connection with their work for the Company) or
use, except in connection with my work for the Company,  Third Party Information

                                       1
<PAGE>


unless expressly authorized by an officer of the Company in writing.

         1.4 No  Improper  Use of  Information  of Prior  Employers  and Others.
During my  employment by the Company I will not  improperly  use or disclose any
confidential information or trade secrets, if any, of any former employer or any
other person to whom I have an  obligation  of  confidentiality,  and I will not
bring onto the premises of the Company any unpublished documents or any property
belonging  to any  former  employer  or  any  other  person  to  whom I have  an
obligation  of  confidentiality  unless  consented  to in writing by that former
employer or person.  I will use in the performance of my duties only information
which is  generally  known and used by  persons  with  training  and  experience
comparable  to my own,  which is common  knowledge  in the industry or otherwise
legally in the public domain, or which is otherwise provided or developed by the
Company.

2.       Assignment of Inventions.

         2.1 Proprietary  Rights.  The term "Proprietary  Rights" shall mean all
trade  secret,  patent,  copyright,  mask work and other  intellectual  property
rights throughout the world.

         2.2 Prior Inventions. Inventions, if any, patented or unpatented, which
I made prior to the  commencement of my employment with the Company are excluded
from the scope of this Agreement.  To preclude any possible uncertainty,  I have
set forth on Attachment B (Previous  Inventions) attached hereto a complete list
of all  Inventions  that I  have,  alone  or  jointly  with  others,  conceived,
developed or reduced to practice or caused to be conceived, developed or reduced
to practice prior to the commencement of my employment with the Company,  that I
consider to be my property or the  property of third  parties and that I wish to
have  excluded  from the scope of this  Agreement  (collectively  referred to as
"Prior Inventions"). If disclosure of any such Prior Invention would cause me to
violate any prior confidentiality  agreement, I understand that I am not to list
such Prior Inventions in Attachment B but am only to disclose a cursory name for
each such invention, a listing of the party(ins) to whom it belongs and the fact
that full disclosure as to such inventions has not been made for that reason.  A
space is provided on  Attachment B for such  purpose.  If no such  disclosure is
attached,  I represent that there are no Prior Inventions.  If, in the course of
my employment  with the Company,  I incorporate a Prior Invention into a Company
product,  process or  machine,  the  Company is hereby  granted and shall have a
nonexclusive,  royalty-free,  irrevocable,  perpetual,  worldwide  license (with
rights to sublicense through multiple tiers of sublicensees) to make, have made,
modify,  use and sell such Prior  Invention.  Notwithstanding  the foregoing,  I
agree  that  I  will  not  incorporate,  or  permit  to be  incorporated,  Prior
Inventions  in any  Company  Inventions  without  the  Company's  prior  written
consent.

         2.3  Assignment  of  Inventions.  Subject to Sections  2.4,  and 2.6, I
hereby  assign and agree to assign in the future  (when any such  Inventions  or
Proprietary  Rights are first  reduced to  practice or first fixed in a tangible
medium, as applicable) to the Company all my right, title and interest in and to
any and all Inventions (and all Proprietary Rights with respect thereto) whether
or not patentable or registrable  under copyright or similar  statutes,  made or
conceived or reduced to practice or learned by me,  either alone or jointly with
others, during the period of my employment with the Company. Inventions assigned
to the Company,  or to a third party as directed by the Company pursuant to this
Section 2, are hereinafter referred to as "Company Inventions."

         2.4  Nonassignable  Inventions.  This  Agreement  does not  apply to an
Invention which qualifies fully as a nonassignable  Invention under Section 2870
of the California Labor Code  (hereinafter  "Section 2870"). I have reviewed the
notification on Attachment A (Limited 

                                       2
<PAGE>

Exclusion  Notification) and agree that my signature acknowledges receipt of the
notification.

         2.5  Obligation  to Keep  Company  Informed.  During  the  period of my
employment and for six (6) months after  termination  of my employment  with the
Company,  I will  promptly  disclose  to the  Company  fully and in writing  all
Inventions  authored,  conceived  or reduced to practice by me,  either alone or
jointly with others.  In addition,  I will promptly  disclose to the Company all
patent  applications filed by me or on my behalf within a year after termination
of employment. At the time of each such disclosure, I will advise the Company in
writing of any  Inventions  that I believe  fully qualify for  protection  under
Section  2870;  and I will at that time  provide to the  Company in writing  all
evidence  necessary  to  substantiate  that  belief.  The  Company  will keep in
confidence and will not use for any purpose or disclose to third parties without
my consent  any  confidential  information  disclosed  in writing to the Company
pursuant  to this  Agreement  relating  to  Inventions  that  qualify  fully for
protection   under  the   provisions  of  Section  2870.  I  will  preserve  the
confidentiality  of any  Invention  that does not fully  qualify for  protection
under Section 2870.

         2.6  Government  or Third  Party.  I also agree to assign all my right,
title and interest in and to any particular  Company Invention to a third party,
including without limitation the United States, as directed by the Company.

         2.7 Works for Hire. I acknowledge that all original works of authorship
which are made by me  (solely  or jointly  with  others)  within the scope of my
employment  and which are  protectable  by copyright  are "works made for hire,"
pursuant to United States Copyright Act (17 U.S.C., Section 101).

         2.8  Enforcement  of Proprietary  Rights.  I will assist the Company in
every proper way to obtain,  and from time to time  enforce,  United  States and
foreign  Proprietary  Rights  relating  to  Company  Inventions  in any  and all
countries.  To that end I will  execute,  verify and deliver such  documents and
perform such other acts (including  appearances as a witness) as the Company may
reasonably request for use in applying for, obtaining,  perfecting,  evidencing,
sustaining and enforcing such Proprietary Rights and the assignment  thereof. In
addition,  I will execute,  verify and deliver  assignments of such  Proprietary
Rights to the Company or its designee.  My obligation to assist the Company with
respect to Proprietary Rights relating to such Company Inventions in any and all
countries  shall  continue  beyond the  termination  of my  employment,  but the
Company shall  compensate me at a reasonable  rate after my termination  for the
time actually spent by me at the Company's request on such assistance.

         In the event the  Company is unable for any  reason,  after  reasonable
effort,  to secure my signature on any document  needed in  connection  with the
actions specified in the preceding paragraph, I hereby irrevocably designate and
appoint the Company and its duly authorized  officers and agents as my agent and
attorney in fact, which appointment is coupled with an interest,  to act for and
in my behalf to execute,  verify and file any such documents and to do all other
lawfully permitted acts to further the purposes of the preceding  paragraph with
the same  legal  force  and  effect  as if  executed  by me. I hereby  waive and
quitclaim to the Company any and all claims, of any nature  whatsoever,  which I
now or may hereafter have for  infringement of any  Proprietary  Rights assigned
hereunder to the Company.

3. Records.  I agree to keep and maintain  adequate and current  records (in the
form of notes, sketches,  drawings and in any other form that may be required by
the Company) of all Proprietary  Information  developed by me and all Inventions
made by me during the period of my  employment  at the  Company,  which  records

                                       3
<PAGE>


shall be available to and remain the sole property of the Company at all times.

4. Additional Activities. I agree that during the period of my employment by the
Company I will not, without the Company's express written consent, engage in any
employment or business  activity which is competitive  with, or would  otherwise
conflict with, my employment by the Company. I agree further that for the period
of my  employment  by the  Company  and for  one  (l)  year  after  the  date of
termination  of my  employment  by the Company I will not induce any employee of
the Company to leave the employ of the Company.

5. No Conflicting  Obligation.  I represent that my performance of all the terms
of this Agreement and as an employee of the Company does not and will not breach
any agreement to keep in confidence  information acquired by me in confidence or
in trust prior to my employment by the Company.  I have not entered into,  and I
agree I will not enter into,  any agreement  either  written or oral in conflict
herewith.

6. Return of Company  Documents.  When I leave the employ of the Company, I will
deliver to the Company any and all drawings,  notes, memoranda,  specifications,
devices,  formulas,  and documents,  together with all copies  thereof,  and any
other  material  containing or disclosing  any Company  Inventions,  Third Party
Information or Proprietary  Information of the Company. I further agree that any
property situated on the Company's premises and owned by the Company,  including
disks and other storage media,  filing  cabinets or other work areas, is subject
to inspection by Company personnel at any time with or without notice.  Prior to
leaving,  I will  cooperate  with the  Company in  completing  and  signing  the
Company's termination statement.

7. Legal and Equitable Remedies. Because my services are personal and unique and
because  I may  have  access  to and  become  acquainted  with  the  Proprietary
Information  of the  Company,  the Company  shall have the right to enforce this
Agreement and any of its provisions by injunction, specific performance or other
equitable  relief,  without  bond and without  prejudice to any other rights and
remedies that the Company may have for a breach of this Agreement.

8. Notices.  Any notices  required or permitted  hereunder shall be given to the
appropriate party at the address specified below or at such other address as the
party shall specify in writing.  Such notice shall be deemed given upon personal
delivery to the appropriate  address or if sent by certified or registered mail,
three (3) days after the date of mailing.

9.  Notification  of New  Employer.  In the event that I leave the employ of the
Company,  I hereby consent to the  notification  of my new employer of my rights
and obligations under this Agreement.

10.      General Provisions.

         10.1 Governing Law;  Consent to Personal  Jurisdiction.  This Agreement
will  be  governed  by and  construed  according  to the  laws of the  State  of
California,  as such  laws are  applied  to  agreements  entered  into and to be
performed  entirely within California  between  California  residents.  I hereby
expressly  consent to the personal  jurisdiction of the state and federal courts
located in Santa Clara County, California for any lawsuit filed there against me
by Company arising from or related to this Agreement.

         10.2 Severability.  In case any one or more of the provisions contained
in this  Agreement  shall,  for any reason,  be held to be  invalid,  illegal or
unenforceable in any respect,  such invalidity,  illegality or  unenforceability
shall not affect the other  provisions  of this  Agreement,  and this  Agreement
shall be construed as if such invalid,  illegal or  unenforceable  provision had
never been  

                                       4
<PAGE>
contained  herein. If moreover,  any one or more of the provisions  contained in
this  Agreement  shall  for any  reason  be held to be  excessively  broad as to
duration,  geographical  scope,  activity or subject,  it shall be  construed by
limiting and reducing it, so as to be enforceable to the extent  compatible with
the applicable law as it shall then appear.

         10.3  Successors  and Assigns.  This  Agreement will be binding upon my
heirs, executors, administrators and other legal representatives and will be for
the benefit of the Company, its successors, and its assigns.

         10.4  Survival.  The  provisions  of this  Agreement  shall survive the
termination of my employment and the assignment of this Agreement by the Company
to any successor in interest or other assignee.

         10.5 Employment.  I agree and understand that nothing in this Agreement
shall  confer  any right with  respect  to  continuation  of  employment  by the
Company,  nor shall it interfere in any way with my right or the Company's right
to terminate my employment at any time, with or without cause.

         10.6 Waiver.  No waiver by the Company of any breach of this  Agreement
shall be a waiver  of any  preceding  or  succeeding  breach.  No  waiver by the
Company of any right under this Agreement  shall be construed as a waiver of any
other right.  The Company shall not be required to give notice to enforce strict
adherence to all terms of this Agreement.

         10.7 Entire Agreement.  The obligations pursuant to Sections 1 and 2 of
this Agreement  shall apply to any time during which I was previously  employed,
or am in the  future  employed,  by the  Company  as a  consultant  if no  other
agreement governs nondisclosure and assignment of inventions during such period.
This  Agreement is the final,  complete and  exclusive  agreement of the parties
with respect to the subject  matter hereof and  supersedes  and merges all prior
discussions  between us. No modification of or amendment to this Agreement,  nor
any  waiver of any rights  under this  Agreement,  will be  effective  unless in
writing and signed by the party to be charged.  Any subsequent change or changes
in my duties,  salary or  compensation  will not affect the validity or scope of
this Agreement.

         This Agreement  shall be effective as of the first day of my employment
with the Company, namely: March 30, 1998.

                                       5
<PAGE>


         I have read this  Agreement  carefully and understand its terms. I have
completely filled out Exhibit B to this Agreement.


Dated:     3/11/98
      --------------------------

  /s/ Joseph D. Keegan
--------------------------------
Joseph D. Keegan

Accepted and Agreed To:


MOLECULAR DEVICES CORPORATION


By: Andre F. Marion
   -----------------------------

Title: President/CEO
      --------------------------

   556 Kingsley Ave.
--------------------------------
(Address)

   Palo Alto, Ca. 94301
--------------------------------


Dated:      3/6/98
      --------------------------


                                       6
<PAGE>

                                  ATTACHMENT A
                         LIMITED EXCLUSION NOTIFICATION

         This is to notify you in accordance with Section 2872 of the California
Labor Code that the  foregoing  Agreement  between you and the Company  does not
require you to assign or offer to assign to the Company any  invention  that you
developed  entirely  on your own time  without  using the  Company's  equipment,
supplies,  facilities or trade secret  information  except for those  inventions
that either:

         1. Relate at the time of  conception  or  reduction  to practice of the
invention  to the  Company's  business,  or actual or  demonstrably  anticipated
research or development of the Company;

         2. Result from any work performed by you for the Company.

         To the  extent a  provision  in the  foregoing  Agreement  purports  to
require  you to  assign  an  invention  otherwise  excluded  from the  preceding
paragraph,  the  provision  is against  the  public  policy of this state and is
unenforceable.

         This  limited  exclusion  does not  apply to any  patent  or  invention
covered by a contract  between the  Company and the United  States or any of its
agencies  requiring  full title to such patent or  invention to be in the United
States.

     I acknowledge receipt of a copy of this notification.




By:
                                              Joseph D. Keegan
                                              3/11/98

Date:

Witnessed by:


_________________________________________
(Printed Name of Representative)



                                       7
<PAGE>

                                  ATTACHMENT B


TO:           Molecular Devices Corporation


FROM:         Joseph D. Keegan


DATE:         3/11/98


SUBJECT: Previous Inventions


1. Except as listed in Section 2 below,  the following is a complete list of all
inventions or  improvements  relevant to the subject  matter of my employment by
Molecular  Devices  (the  "Company")  that have been made or  conceived or first
reduced to practice by me alone or jointly with others prior to my engagement by
the Company:

         :   No inventions or improvements.

         :   See below:

                                                                      __________
 

                                                                      __________


                                                                      __________


         :   Additional sheets attached.

2. Due to a prior  confidentiality  agreement,  I cannot complete the disclosure
under  Section 1 above with  respect to  inventions  or  improvements  generally
listed below, the proprietary rights and duty of confidentiality with respect to
which I owe to the following party(ins):


                Invention               or Party(ies)         Relationship
                Improvement             

1.       --------------------------     -------------------   ------------------

2.       --------------------------     -------------------   ------------------

3.       --------------------------     -------------------   ------------------


                                       8