THERMO INSTRUMENT SYSTEMS INC.

                THERMO BIOANALYSIS CORPORATION NONQUALIFIED STOCK OPTION PLAN

                     As amended and restated effective as of June 8, 1999


1.      Purpose

        This Nonqualified Stock Option Plan (the "Plan") is intended to
encourage ownership of Common Stock (the "Common Stock"), of Thermo BioAnalysis
Corporation ("Subsidiary"), a subsidiary of Thermo Instrument Systems Inc. (the
"Company"), by persons selected by the Board of Directors (or a committee
thereof) in its sole discretion, including directors, executive officers, key
employees and consultants of the Company and its subsidiaries, and to provide
additional incentive for them to promote the success of the business of the
Company and Subsidiary. The Plan is intended to be a nonstatutory stock option
plan.

2.      Effective Date of the Plan

        The Plan shall become effective when adopted by the Board of Directors
of the Company.

3.      Stock Subject to Plan

        Subject to adjustment as provided in Section 11, the total number of
shares of Common Stock reserved and available for issuance under the Plan shall
be 100,000 shares. Shares to be issued upon the exercise of options granted
under the Plan shall be shares of Subsidiary beneficially owned by the Company.
If any option expires or terminates for any reason without having been exercised
in full, the unpurchased shares subject thereto shall again be available for
options thereafter to be granted.

4.      Administration

        The Plan will be administered by the Board of Directors of the Company
(the "Board"). Subject to the provisions of the Plan, the Board shall have
complete authority, in its discretion, to make the following determinations with
respect to each option to be granted by the Company: (a) the person to receive
the option (the "Optionee"); (b) the time of granting the option; (c) the number
of shares subject thereto; (d) the option price; (e) the option period; and (f)
the terms and conditions of options granted under the Plan (including terms and
conditions relating to events of merger, consolidation, dissolution and
liquidation, change of control, vesting, forfeiture, restrictions, dividends and
interest, if any, on deferred amounts); (g) waive compliance by an optionee with
any obligation to be performed by him or her under an option; (h) waive any term
or condition of an option; (i) cancel an existing option in whole or in part
with the consent of an Optionee; (j) grant replacement options; (k) accelerate
the vesting or lapse of any restrictions of any option; and (l) adopt the form
of instruments evidencing options under the Plan and change such forms from time
to time. In making such determinations, the Board may take into account the
nature of the services rendered by the Optionees, their present and potential
contributions to the success of the Company and/or one or more of its
subsidiaries, and such other factors as the Board in its discretion shall deem
relevant. Subject to the provisions of the Plan, the Board shall also have
complete authority to interpret the Plan, to prescribe, amend, and rescind rules
and regulations relating to it, to determine the terms and provisions of the
respective option agreements (which need not be identical), and to make all
other determinations necessary or advisable for the administration of the Plan.
Any interpretation by the Board of the terms and provisions of the Plan or any
Award thereunder and the administration thereof, and all action taken by the
Board, shall be final, binding and conclusive on all parties and any person
claiming under or through any party. No Director shall be liable for any action
or determination made in good faith. The Board may, to the full extent permitted
by law, delegate any or all of its responsibilities under the Plan to a
committee (the "Committee") appointed by the Board and consisting of two or more
members of the Board, each of whom shall be deemed a "disinterested person"
within the meaning of Rule 16b-3 (or any successor rule) of the Securities
Exchange Act of 1934 (the "Exchange Act").

5.      Eligibility

        An option may be granted to any person selected by the Board in its sole
discretion.

6.      Time of Granting Options

        The granting of an option shall take place at the time specified by the
Board. Only if expressly so provided by the Board shall the granting of an
option be regarded as taking place at the time when a written option agreement
shall have been duly executed and delivered by or on behalf of the Company and
the Optionee to whom such option shall be granted. The agreement shall provide,
among other things, that it does not confer upon an Optionee any right to
continue in the employ of the Company and/or one or more of its subsidiaries or
to continue as a director or consultant of the Company, and that it does not
interfere in any way with the right of the Company or any such subsidiary to
terminate the employment of the Optionee at any time if the Optionee is an
employee, to remove the Optionee as a director of the Company if the Optionee is
a director, or to terminate the services of the Optionee if the Optionee is a
consultant.

7.      Option Period

        An option may become exercisable immediately or in such installments,
cumulative or noncumulative, as the Board may determine.

8.      Exercise of Option

        An option may be exercised in accordance with its terms by written
notice of intent to exercise the option, specifying the number of shares of
stock with respect to which the option is then being exercised. The notice shall
be accompanied by payment in the form of cash or shares of Subsidiary Common
Stock (the "Tendered Shares") with a then current market value equal to the
option price of the shares to be purchased; provided, however, that such
Tendered Shares shall have been acquired by the Optionee more than six months
prior to the date of exercise, unless such requirement is waived in writing by
the Company. Against such payment the Company shall deliver or cause to be
delivered to the Optionee a certificate for the number of shares then being
purchased, registered in the name of the Optionee or other person exercising the
option. If any law or applicable regulation of the Securities and Exchange
Commission or other body having jurisdiction in the premises shall require the
Company, Subsidiary or the Optionee to take any action in connection with shares
being purchased upon exercise of the option, exercise of the option and delivery
of the certificate or certificates for such shares shall be postponed until
completion of the necessary action, which shall be taken at the Company's
expense.

9.      Transferability

        Except as may be authorized by the Board, in its sole discretion, no
Option may be transferred other than by will or the laws of descent and
distribution, and during a Optionee's lifetime an option requiring exercise may
be exercised only by him or her (or in the event of incapacity, the person or
persons properly appointed to act on his or her behalf). The Board may, in its
discretion, determine the extent to which options granted to an Optionee shall
be transferable, and such provisions permitting or acknowledging transfer shall
be set forth in the written agreement evidencing the option executed and
delivered by or on behalf of the Company and the Optionee.

10.     Vesting, Restrictions and Termination of Options

        The Board, in its sole discretion, may determine the manner in which
options shall vest, the rights of the Company to repurchase the shares issued
upon the exercise of any option and the manner in which such rights shall lapse,
and the terms upon which any option granted shall terminate. The Board shall
have the right to accelerate the date of exercise of any installment or to
accelerate the lapse of the Company's repurchase rights. All of such terms shall
be specified in a written option agreement executed and delivered by or on
behalf of the Company and the Optionee to whom such option shall be granted.

11.     Adjustments in the Event of Certain Transactions

        (a) In the event of a stock dividend, stock split or combination of
shares, or other distribution with respect to holders of Common Stock other than
normal cash dividends, the Board will make (i) appropriate adjustments to the
maximum number of shares that may be delivered under the Plan under Section 3
above, and (ii) appropriate adjustments to the number and kind of shares of
stock or securities subject to Options then outstanding or subsequently granted,
any exercise prices relating to Options and any other provisions of Awards
affected by such change.

        (b) In the event of any recapitalization, merger or consolidation
involving the Company, any transaction in which the Company becomes a subsidiary
of another entity, any sale or other disposition of all or a substantial portion
of the assets of the Company, any transaction which results in Thermo Electron
Corporation ceasing to be the beneficial owner of a majority of the
then-outstanding shares of Common Stock, or any similar transaction, as
determined by the Board, the Board in its discretion may make appropriate
adjustments to outstanding Options to avoid distortion in the operation of the
Plan.

12.     Change in Control

        12.1   Impact of Event

        In the event of a "Change in Control" as defined in Section 12.2, the
following provisions shall apply, unless the agreement evidencing the Option
otherwise provides (by specific explicit reference to Section 12.2 below). If a
Change in Control occurs while any Options are outstanding, then, effective upon
the Change in Control, (i) each outstanding stock option granted under the Plan
that was not previously exercisable and vested shall become immediately
exercisable in full and will no longer be subject to a right of repurchase by
the Company, (ii) each outstanding Option subject to restrictions and to the
extent not fully vested, shall be deemed to be fully vested, free of
restrictions and no longer subject to a right of repurchase by the Company, and
(iii) performance of other conditions (other than conditions relating solely to
the passage of time, continued employment or affiliation) will continue to apply
unless otherwise provided in the agreement evidencing the Option or in any other
agreement between the Optioneet and the Company or unless otherwise agreed by
the Board.

        12.2   Definition of "Change in Control"

        "Change in Control" means an event or occurrence set forth in any one or
more of subsections (a) through (d) below (including an event or occurrence that
constitutes a Change in Control under one of such subsections but is
specifically exempted from another such subsection):

        (a) the acquisition by an individual, entity or group (within the
meaning of Section 13(d)(3) or 14(d)(2) of the Exchange Act) (a "Person") of
beneficial ownership of any capital stock of Thermo Electron Corporation
("Thermo Electron") if, after such acquisition, such Person beneficially owns
(within the meaning of Rule 13d-3 promulgated under the Exchange Act) 40% or
more of either (i) the then-outstanding shares of common stock of Thermo
Electron (the "Outstanding TMO Common Stock") or (ii) the combined voting power
of the then-outstanding securities of Thermo Electron entitled to vote generally
in the election of directors (the "Outstanding TMO Voting Securities");
provided, however, that for purposes of this subsection (a), the following
acquisitions shall not constitute a Change in Control: (i) any acquisition by
Thermo Electron, (ii) any acquisition by any employee benefit plan (or related
trust) sponsored or maintained by Thermo Electron or any corporation controlled
by Thermo Electron, or (iii) any acquisition by any corporation pursuant to a
transaction which complies with clauses (i) and (ii) of subsection (c) of this
definition; or

        (b) such time as the Continuing Directors (as defined below) do not
constitute a majority of the Board of Directors of Thermo Electron (the "Thermo
Board") (or, if applicable, the Board of Directors of a successor corporation to
Thermo Electron), where the term "Continuing Director" means at any date a
member of the Thermo Board (i) who was a member of the Thermo Board as of July
1, 1999 or (ii) who was nominated or elected subsequent to such date by at least
a majority of the directors who were Continuing Directors at the time of such
nomination or election or whose election to the Thermo Board was recommended or
endorsed by at least a majority of the directors who were Continuing Directors
at the time of such nomination or election; provided, however, that there shall
be excluded from this clause (ii) any individual whose initial assumption of
office occurred 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 the
Thermo Board; or

        (c) the consummation of a merger, consolidation, reorganization,
recapitalization or statutory share exchange involving Thermo Electron or a sale
or other disposition of all or substantially all of the assets of Thermo
Electron in one or a series of transactions (a "Business Combination"), unless,
immediately following such Business Combination, each of the following two
conditions is satisfied: (i) all or substantially all of the individuals and
entities who were the beneficial owners of the Outstanding TMO Common Stock and
Outstanding TMO Voting Securities immediately prior to such Business Combination
beneficially own, directly or indirectly, more than 60% of the then-outstanding
shares of common stock and the combined voting power of the then-outstanding
securities entitled to vote generally in the election of directors,
respectively, of the resulting or acquiring corporation in such Business
Combination (which shall include, without limitation, a corporation which as a
result of such transaction owns Thermo Electron or substantially all of Thermo
Electron's assets either directly or through one or more subsidiaries) (such
resulting or acquiring corporation is referred to herein as the "Acquiring
Corporation") in substantially the same proportions as their ownership,
immediately prior to such Business Combination, of the Outstanding TMO Common
Stock and Outstanding TMO Voting Securities, respectively; and (ii) no Person
(excluding the Acquiring Corporation or any employee benefit plan (or related
trust) maintained or sponsored by Thermo Electron or by the Acquiring
Corporation) beneficially owns, directly or indirectly, 40% or more of the then
outstanding shares of common stock of the Acquiring Corporation, or of the
combined voting power of the then-outstanding securities of such corporation
entitled to vote generally in the election of directors; or

        (d) approval by the stockholders of Thermo Electron of a complete
liquidation or dissolution of Thermo Electron.

13.     Limitation of Rights in Option Stock

        The Optionees shall have no rights as stockholders in respect of shares
as to which their options shall not have been exercised, certificates issued and
delivered and payment as herein provided made in full, and shall have no rights
with respect to such shares not expressly conferred by this Plan.

14.     Stock Reserved

        The Company shall at all times during the term of the options reserve
and keep available such number of shares of the Common Stock as will be
sufficient to satisfy the requirements of this Plan and shall pay all other fees
and expenses necessarily incurred by the Company in connection therewith.

15.     Securities Laws Restrictions

        Each Optionee exercising an option, at the request of the Company, will
be required to give a representation in form satisfactory to counsel for the
Company that he will not transfer, sell or otherwise dispose of the shares
received upon exercise of the option at any time purchased by him, upon exercise
of any portion of the option, in a manner which would violate the Securities Act
of 1933, as amended, and the regulations of the Securities and Exchange
Commission thereunder and the Company may, if required or at its discretion,
make a notation on any certificates issued upon exercise of options to the
effect that such certificate may not be transferred except after receipt by the
Company of an opinion of counsel satisfactory to it to the effect that such
transfer will not violate such Act and such regulations.

16.     Tax Withholding

        The Company shall have the right to deduct from payments of any kind
otherwise due to an Optionee any federal, state or local taxes of any kind
required by law to be withheld with respect to any shares issued upon exercise
of options under the Plan (the "withholding requirements"). The Board will have
the right to require that the Optionee or other appropriate person remit to the
Company an amount sufficient to satisfy the withholding requirements, or make
other arrangements satisfactory to the Board with regard to such requirements,
prior to the delivery of any Common Stock pursuant to exercise of an option. If
and to the extent that such withholding is required, the Board may permit the
Optionee or such other person to elect at such time and in such manner as the
Board provides to have the Company hold back from the shares to be delivered, or
to deliver to the Company, Common Stock having a value calculated to satisfy the
withholding requirements.

17.     Termination and Amendment

        The Plan shall remain in full force and effect until terminated by the
Board. Subject to the last sentence of this Section 17, the Board may at any
time or times amend the Plan or any outstanding Option for any purpose that may
at the time be permitted by law, or may at any time terminate the Plan as to any
further grants of Options. No amendment of the Plan or any agreement evidencing
Options under the Plan may adversely affect the rights of any participant under
any Option previously granted without such participant's consent.