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                                   VYSIS, INC.
                           1998 LONG TERM INCENTIVE PLAN





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                                      VYSIS, INC.

                                      Certificate

         I, _____________ , _____________ of Vysis, Inc. having in my custody 
and possession the corporate records of said corporation, do hereby certify 
that attached hereto is a true and correct copy of the Vysis, Inc. 1998 Long 
Term Incentive Plan as in effect as of October 1, 1998.

         WITNESS my hand this ___ day of ________________, 1999.




                                                 As Aforesaid



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                                 VYSIS, INC.
                        1998 LONG TERM INCENTIVE PLAN


         1. PURPOSE. The purpose of this Vysis, Inc. 1998 Long Term Incentive 
Plan (the "Plan") is to increase stockholder value and to advance the 
interests of Vysis, Inc. ("Vysis") and its subsidiaries (collectively, the 
"Company") by awarding equity and performance based incentives designed to 
attract, retain and motivate employees. As used in the Plan, the term 
"subsidiary" means any business, whether or not incorporated, in which Vysis 
has an ownership interest.

         2.  ADMINISTRATION.

                  2.1. ADMINISTRATION BY COMMITTEE. The Plan shall be 
administered by the Compensation Committee of the Board of Directors of Vysis 
or a subcommittee thereof (the "Committee"), which Committee shall consist of 
two or more persons who constitute "non-employee directors" within the 
meaning of Rule 16b-3 promulgated under the Securities Exchange Act of 1934, 
as amended (the "Exchange Act") and "outside directors" within the meaning of 
Treas. Reg. Section 1.162-27(e)(3).

                  2.2. AUTHORITY. Subject to the provisions of the Plan, the 
Committee shall have the authority to (a) manage and control the operation of 
the Plan, (b) interpret and construe the provisions of the Plan, and 
prescribe, amend and rescind rules and regulations relating to the Plan, (c) 
make Awards under the Plan, in such forms and amounts and subject to such 
restrictions, limitations and conditions as it deems appropriate, including, 
without limitation, Awards which are made in combination with or in tandem 
with other Awards (whether or not contemporaneously granted) or compensation 
or in lieu of current or deferred compensation, (d) modify the terms of, 
cancel and reissue, or repurchase outstanding Awards (including, but not 
limited to, repurchasing or settling any Option (as defined in subsection 
6.1) in cash upon a Change in Control (as defined in subsection 12.2)), (e) 
prescribe the form of agreement, certificate or other instrument evidencing 
any Award under the Plan, (f) correct any defect or omission and reconcile 
any inconsistency in the Plan or in any Award hereunder, (g) extend the 
exercise or vesting date of any Award under the Plan, (h) accelerate the 
vesting or exercise date of any Award under the plan, and (i) make all other 
determinations and take all other actions as it deems necessary or desirable 
for the implementation and administration of the Plan; provided, however, 
that in no event shall the Committee cancel or modify any Option granted on 
or after October 1, 1998 for the purpose of reissuing an additional option to 
the option holder at a lower exercise price. The determination of the 
Committee on matters within its authority shall be conclusive and binding on 
the Company and all other persons.

         3. PARTICIPATION. Subject to the terms and conditions of the Plan, 
the Committee shall determine and designate, from time to time, from among 
the employees of the Company who are key executives or managerial employees 
and consultants who provide services to the Company those persons who will be 
granted one or more Awards under the Plan, and thereby become "Participants" 
in the Plan. In the discretion of the Committee, and subject to the terms of 
the


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Plan, a Participant may be granted any Award permitted under the provisions 
of the Plan, and more than one Award may be granted to a Participant; 
provided, however, that only employees of the Company may be awarded 
Incentive Stock Options (as defined in subsection 6.1) under the Plan. Except 
as otherwise agreed by the Committee and the Participant, or except as 
otherwise provided in the Plan, an Award under the Plan shall not affect any 
previous Award under the Plan or an award under any other plan maintained by 
the Company. For purposes of the Plan, the term "Award" shall mean any award 
or benefit granted to any Participant under the Plan.

         4. DEFINITION OF FAIR MARKET VALUE. For purposes of the Plan, the 
"Fair Market Value" of a share of common stock of Vysis ("Stock") as of any 
date shall be the closing market composite price for such Stock as reported 
on NASDAQ on that date or, if Stock is not traded on that date, on the 
immediately preceding date on which Stock was traded.

         5. SHARES SUBJECT TO THE PLAN.

         5.1. NUMBER OF SHARES RESERVED. The shares of Stock with respect to 
which Awards may be made under the Plan shall be shares currently authorized 
but unissued or currently held or subsequently acquired by Vysis as treasury 
shares, including shares purchased in the open market or in private 
transactions. Subject to the provisions of subsection 5.4, the number of 
shares of Stock which may be issued with respect to Awards under the Plan 
shall not exceed 1.5 million shares.

         5.2. INDIVIDUAL LIMITS ON AWARDS. Notwithstanding any other 
provision of the Plan to the contrary, the maximum aggregate number of shares 
of Stock that may be granted or awarded to any Participant under the Plan for 
any calendar year shall be 250,000 and the maximum aggregate cash payout with 
respect to grants or awards under the Plan in any calendar year to any 
Covered Employee (within the meaning of section 162(m) of the Internal 
Revenue Code of 1986, as amended (the "Code")), shall be $25,000,000. The 
determination made under the foregoing provisions of this subsection 5.2 
shall be based on the shares subject to the Awards at the time of grant, 
regardless of when the Awards become exercisable.

         5.3.     REUSAGE OF SHARES.

         (a)      In the event of the exercise or termination (by reason of
                  forfeiture, expiration, cancellation, surrender or otherwise)
                  of any Award under the Plan, that number of shares of Stock
                  that was subject to the Award but not delivered shall again be
                  available for Awards under the Plan.

         (b)      In the event that shares of Stock are delivered under the Plan
                  as a Stock Award (as defined in Section 8) and are thereafter
                  forfeited or reacquired by the Company pursuant to rights
                  reserved upon the award thereof, such forfeited or reacquired
                  shares shall again be available for Awards under the Plan.


                                         -2-

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         (c)      Notwithstanding the provisions of paragraphs (a) or (b), the
                  following shares shall not be available for reissuance under
                  the Plan: (i) shares with respect to which the Participant has
                  received the benefits of ownership (other than voting rights),
                  either in the form of dividends or otherwise; (ii) shares
                  which are withheld from any award or payment under the Plan to
                  satisfy tax withholding obligations (as described in
                  subsection 11.4); (iii) shares which are surrendered to
                  fulfill tax obligations (as described in subsection 11.4);
                  and (iv) shares which are surrendered in payment of the
                  Option Price (as defined in subsection 6.3) upon the exercise
                  of an Option.

         5.4. ADJUSTMENTS TO SHARES RESERVED. In the event of any merger, 
consolidation, reorganization, recapitalization, spinoff, stock dividend, 
stock split, reverse stock split, exchange or other distribution with respect 
to shares of Stock or other change in the corporate structure or 
capitalization affecting the Stock, the type and number of shares of Stock 
which are or may be subject to awards under the Plan and the terms of any 
outstanding awards (including the price at which shares of Stock may be 
issued pursuant to an outstanding award) shall be equitably adjusted by the 
Committee, in its sole discretion, to preserve the value of benefits awarded 
or to be awarded to Participants under the Plan.

         6.  OPTIONS.

         6.1. DEFINITIONS. The grant of an "Option" under this Section 6 
entitles the Participant to purchase shares of Stock at the Option Price 
(determined under subsection 6.3), subject to the terms of this Section 6. 
Options granted under this Section 6 may be either Incentive Stock Options or 
Non-Qualified Stock Options, as determined in the discretion of the 
Committee. An "Incentive Stock Option" is an Option that is intended to 
satisfy the requirements applicable to an "incentive stock option" described 
in section 422(b) of the Code. A "Non-Qualified Stock Option" is an Option 
that is not intended to be an "incentive stock option" as that term is 
described in section 422(b) of the Code.

         6.2. RESTRICTIONS RELATING TO INCENTIVE STOCK OPTIONS. To the extent 
that the aggregate fair market value of Stock with respect to which Incentive 
Stock Options are exercisable for the first time by any individual during any 
calendar year (under all plans of the Company) exceeds $100,000, such options 
shall be treated as Non-Qualified Stock Options, to the extent required by 
section 422 of the Code.

         6.3. OPTION PRICE. The price at which shares of Stock may be 
purchased upon the exercise of an Option (the "Option Price") shall be 
established by the Committee or shall be determined by a method established 
by the Committee at the time the Option is granted; provided, however, that 
in no event shall such price be less than the greater of: (i) 100% of the 
Fair Market Value (as defined in Section 4) of a share of Stock as of the 
date on which the Option is granted; or (ii) the par value of a share of 
Stock on such date.

                                       -3-


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         6.4. EXERCISE. Except as otherwise expressly provided in the Plan, 
an Option may be exercised, in whole or in part, in accordance with terms and 
conditions established by the Committee at the time of grant; provided, 
however, that no Option shall be exercisable after the Expiration Date (as 
defined in Section 10) applicable to that Option. The full Option Price of 
each share of Stock purchased upon the exercise of any Option shall be paid 
at the time of such exercise (except that, in the case of a cashless exercise 
arrangement approved by the Committee, payment may be made as soon as 
practicable after the exercise) and, as soon as practicable thereafter, a 
certificate representing the shares so purchased shall be delivered to the 
person entitled thereto. The Option Price shall be payable in cash or in 
shares of Stock (valued at Fair Market Value as of the day of exercise), or 
in any combination thereof, as determined by the Committee and, to the extent 
provided by the Committee, a Participant may elect to pay the Option Price 
upon the exercise of an Option through a cashless exercise arrangement. The 
exercise of an Option will result in the surrender of the corresponding 
rights under a tandem Stock Appreciation Right, if any.

         6.5. POST-EXERCISE LIMITATIONS. The Committee, in its discretion, 
may impose such restrictions on shares of Stock acquired pursuant to the 
exercise of an Option (including stock acquired pursuant to the exercise of a 
tandem Stock Appreciation Right) as it determines to be desirable, including, 
without limitation, restrictions relating to disposition of the shares and 
forfeiture restrictions based on service, performance, Stock ownership by the 
Participant, and such other factors as the Committee determines to be 
appropriate.

         7.       STOCK APPRECIATION RIGHTS

         7.1. DEFINITION. Subject to the terms of this Section 7, a "Stock 
Appreciation Right" granted under the Plan entitles the Participant to 
receive, in cash or Stock, value equal to all or a portion of the excess of: 
(a) the Fair Market Value of a specified number of shares of Stock at the 
time of exercise; over (b) a specified price which shall not be less than 
100% of the Fair Market Value of the Stock at the time the Stock Appreciation 
Right is granted, or, if granted in tandem with an Option, the exercise price 
with respect to shares under the tandem Option.

         7.2. EXERCISE. If a Stock Appreciation Right is not in tandem with 
an Option, then the Stock Appreciation Right shall be exercisable in 
accordance with the terms established by the Committee in connection with 
such rights after the Expiration Date applicable to that Stock Appreciation 
Right. If a Stock Appreciation Right is in tandem with an Option, then the 
Stock Appreciation Right shall be exercisable at the time the tandem Option 
is exercisable. The exercise of a Stock Appreciation Right will result in the 
surrender of the corresponding rights under the tandem Option.

         7.3. SETTLEMENT OF AWARD. Upon the exercise of a Stock Appreciation 
Right, the value to be distributed to the Participant, in accordance with 
subsection 7.1, shall be distributed in shares of Stock (valued at their Fair 
Market Value at the time of exercise), in cash, or in a combination thereof, 
in the discretion of the Committee.


                                       -4-

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         7.4. POST-EXERCISE LIMITATIONS. The Committee, in its discretion, 
may impose such restrictions on shares of Stock acquired pursuant to the 
exercise of a Stock Appreciation Right as it determines to be desirable, 
including, without limitation, restrictions relating to disposition of the 
shares and forfeiture restrictions based on service, performance, ownership 
of Stock by the Participant, and such other factors as the Committee 
determines to be appropriate.

         8.  STOCK AWARDS.

         8.1. DEFINITION. Subject to the terms of this Section 8, a "Stock 
Award" under the Plan is a grant of shares of Stock to a Participant, the 
earning, vesting or distribution of which is subject to one or more 
conditions established by the Committee. Such conditions may relate to events 
(such as performance or continued employment) occurring before or after the 
date the Stock Award is granted, or the date the Stock is earned by, vested 
in or delivered to the Participant. If the vesting of Stock Awards is subject 
to conditions occurring after the date of grant, the period beginning on the 
date of grant of a Stock Award and ending on the vesting or forfeiture of 
such Stock (as applicable) is referred to as the "Restricted Period". Stock 
Awards may provide for delivery of the shares of Stock at the time of grant, 
or may provide for a deferred delivery date.

         8.2. TERMS AND CONDITIONS OF AWARDS. Beginning on the date of grant 
(or, if later, the date of distribution) of shares of Stock comprising a 
Stock Award, and including any applicable Restricted Period, the Participant, 
as owner of such shares, shall have the right to vote such shares; provided, 
however, that payment of dividends with respect to Stock Awards shall be 
subject to the following:

         (a)      On and after date that a Participant has a fully earned and
                  vested right to the shares comprising a Stock Award, and the
                  shares have been distributed to the Participant, the
                  Participant shall have all dividend rights (and other rights)
                  of a stockholder with respect to such shares.

         (b)      Prior to the date that a Participant has a fully earned and
                  vested right to the shares comprising a Stock Award, the
                  Committee, in its sole discretion, may award Dividend Rights
                  (as defined below) with respect to such shares.

         (c)      On and after the date that a Participant has a fully earned
                  and vested right to the shares comprising a Stock Award, but
                  before the shares have been distributed to the Participant,
                  the Participant shall be entitled to Dividend Rights with
                  respect to such shares, at the time and in the form determined
                  by the Committee.

A "Dividend Right" with respect to shares comprising a Stock Award shall 
entitle the Participant, as of each dividend payment date, to an amount equal 
to the dividends payable with respect to a share of Stock multiplied by the 
number of such shares. Dividend Rights shall be settled in cash or in shares 
of Stock, as determined by the Committee, shall be payable at the time and in 
the form determined by the Committee, and shall be subject to such other 
terms and conditions as the Committee may determine.


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         9.  PERFORMANCE UNITS.

         9.1. DEFINITION. Subject to the terms of this Section 9, the Award 
of "Performance Units" under the Plan entitles the Participant to receive 
value for the units at the end of a Performance Period to the extent provided 
under the Award. The number of units earned, and the value received for them, 
will be contingent on the degree to which the performance measures 
established at the time of grant of the Award are met. For purposes of the 
Plan, the "Performance Period" with respect to the award of any Performance 
Units shall be the period over which the applicable performance is to be 
measured.

         9.2. TERMS AND CONDITIONS OF AWARDS. For each Participant, the 
Committee will determine the value of units, which may be stated either in 
cash or in units representing shares of Stock; the performance measures used 
for determining whether the Performance Units are earned; the Performance 
Period during which the performance measures will apply; the relationship 
between the level of achievement of the performance measures and the degree 
to which Performance Units are earned; whether, during or after the 
Performance Period, any revision to the performance measures or Performance 
Period should be made to reflect significant events or changes that occur 
during the Performance Period; and the number of earned Performance Units 
that will be paid in cash and the number of earned Performance Units to be 
paid in shares of Stock.

         9.3.  SETTLEMENT.  Settlement of Performance Units shall be subject 
to the following:

         (a)      the Committee will compare the actual performance to the
                  performance measures established for the Performance Period
                  and determine the number of units as to which settlement is to
                  be made, and the value of such units.

         (b)      Settlement of units earned shall be wholly in cash, wholly in
                  Stock or in a combination of the two, to be distributed in a
                  lump sum or installments, as determined by the Committee.

                  (i)      For Performance Units stated in units representing
                           shares of Stock when granted, one share of Stock will
                           be distributed for each unit earned, or cash will be
                           distributed for each unit earned equal to either (A)
                           the Fair Market Value of a share of Stock at the end
                           of the Performance Period or (B) the average Stock
                           value over a period determined by the Committee.

                  (ii)     For Performance Units stated in cash when granted,
                           the value of each unit earned will be distributed in
                           its initial cash value, or shares of Stock will be
                           distributed based on the cash value of the units
                           earned divided by (A) the Fair Market Value of a
                           share of Stock at the end of the Performance Period
                           or (B) the average Stock value over a period
                           determined by the Committee.


                                       -6-

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         (c)      Shares of Stock distributed in settlement of the units shall
                  be subject to such vesting requirements and other conditions,
                  if any, as the Committee shall determine.

         9.4. TERMINATION DURING PERFORMANCE PERIOD. If a Participant's 
termination of employment with the Company occurs during a Performance Period 
with respect to any Performance Units granted to him, the Committee may 
determine that the Participant will be entitled to settlement of all or any 
portion of the Performance Units as to which he would otherwise be eligible, 
and may accelerate the determination of the value and settlement of such 
Performance Units or make such other adjustments as the Committee, in its 
sole discretion, deems desirable.

         10. EXPIRATION OF AWARDS. The "Expiration Date" with respect to an 
Award under the Plan means the date established as the Expiration Date by the 
Committee at the time of the grant; provided, however, that the Expiration 
Date with respect to any Award shall not be later than the earliest to occur 
of:

         (a)      the ten-year anniversary of the date on which the Award is 
                  granted;

         (b)      if the Participant's termination of employment with the
                  Company occurs on account of disability, the one-year
                  anniversary of such termination of employment;

         (c)      if the Participant's termination of employment with the
                  Company occurs by reason of retirement, the three-year
                  anniversary of such termination of employment;

         (d)      the three-month anniversary of the Participant's death, 
                  either while employed or thereafter; or

         (e)      if the Participant's termination of employment with the
                  Company occurs for reasons other than retirement or
                  disability, the three-month anniversary of such termination of
                  employment.

If a Stock Appreciation Right is in tandem with an Option, then the 
"Expiration Date" for the Stock Appreciation Right shall be the Expiration 
Date for the related Option.

         11.      MISCELLANEOUS.

         11.1. EFFECTIVE DATE. The Plan shall be effective upon its adoption 
by the Board of Directors of Vysis (the "Board"). The Plan shall be unlimited 
in duration and, in the event of Plan termination, shall remain in effect as 
long as any Awards under it are outstanding; provided, however, that no 
Incentive Stock Options may be granted under the Plan on a date that is more 
than ten years from the date the Plan is adopted.


                                       -7-

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         11.2. LIMIT ON DISTRIBUTION. Distribution of shares of Stock or 
other amounts under the Plan shall be subject to the following:

         (a)      Notwithstanding any other provision of the Plan, Vysis shall
                  have no liability to deliver any shares of Stock under the
                  Plan or make any other distribution of benefits under the Plan
                  unless such delivery or distribution would comply with all
                  applicable laws and the applicable requirements of any
                  securities exchange or similar entity.

         (b)      In the case of a Participant who is subject to Section 16(a)
                  and 16(b) of the Exchange Act, the Committee may, at any time,
                  add such conditions and limitations to any Award to such
                  Participant, or any feature of any such Award, as the
                  Committee, in its sole discretion, deems necessary or
                  desirable to comply with Section 16(a) or 16(b) and the rules
                  and regulations thereunder or to obtain any exemption
                  therefrom.

         (c)      To the extent that the Plan provides for issuance of
                  certificates to reflect the transfer of shares of Stock, the
                  transfer of such shares may be effected on a non-certificated
                  basis, to the extent not prohibited by applicable law or the
                  rules of any stock exchange.

         11.3. PERFORMANCE-BASED COMPENSATION. To the extent that the 
Committee determines that it is necessary or desirable to conform any Awards 
under the Plan with the requirements applicable to "Performance-Based 
Compensation", as that term is used in section 162(m)(4)(C) of the Code, it 
may, at or prior to the time an Award is granted, take such steps and impose 
such restrictions with respect to such Award as it determines to be necessary 
or desirable.

         11.4. WITHHOLDING. All Awards and other payments under the Plan are 
subject to withholding of all applicable taxes, which withholding obligations 
may be satisfied, with the consent of the Committee, through the surrender of 
shares of Stock which the Participant already owns, or to which a Participant 
is otherwise entitled under the Plan.

         11.5. TRANSFERABILITY. Awards under the Plan are not transferable 
except as designated by a Participant by will or by the laws of descent and 
distribution. To the extent that the Participant who receives an Award under 
the Plan has the right to exercise such Award, the Award may be exercised 
during the lifetime of the Participant only by the Participant.

         11.6. NOTICES. Any notice or document required to be filed with the 
Committee under the Plan will be properly filed if delivered or mailed by 
registered mail, postage prepaid, to the Committee, in care of Vysis, at its 
principal executive offices. The Committee may, by advance written notice to 
affected persons, revise such notice procedure from time to time. Any notice 
required under the Plan (other than a notice of election) may be waived by 
the person entitled to notice.


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         11.7. FORM AND TIME OF ELECTIONS. Unless otherwise specified herein, 
each election required or permitted to be made by any Participant or other 
person entitled to benefits under the Plan, and any permitted modification or 
revocation thereof, shall be in writing filed with the Committee at such 
times, in such form, and subject to such restrictions and limitations, not 
inconsistent with the terms of the Plan, as the Committee shall require.

         11.8. AGREEMENT WITH VYSIS. At the time of an Award to a Participant 
under the Plan, the Committee may require a Participant to enter into an 
agreement with Vysis (the "Agreement") in a form specified by the Committee, 
agreeing to the terms and conditions of the Plan and to such additional terms 
and conditions, not inconsistent with the Plan, as the Committee may, in its 
sole discretion, prescribe.

         11.9.  LIMITATION OF IMPLIED RIGHTS.

         (a)      Neither a Participant nor any other person shall, by reason 
                  of the Plan, acquire any right in or title to any assets, 
                  funds or property of the Company whatsoever, including, 
                  without limitation, any specific funds, assets, or other
                  property which the Company, in its sole discretion, may set
                  aside in anticipation of a liability under the Plan.  A
                  Participant shall have only a contractual right to benefits
                  or amounts, if any, payable under the Plan, unsecured by any
                  assets of the Company. Nothing contained in the Plan shall
                  constitute a guarantee by the Company that the assets of
                  the Company shall be sufficient to pay any amounts or
                  benefits to any person.

         (b)      The Plan does not constitute a contract of employment, and 
                  selection as a Participant will not give any employee the 
                  right to be retained in the employ of the Company, nor any 
                  right or claim to any benefit or payment under the Plan,
                  unless such right or claim has specifically accrued under
                  the terms of the Plan.  Except as otherwise provided in the
                  Plan, no Award under the Plan shall confer upon the holder
                  thereof any right as a shareholder of Vysis prior to the date
                  on which he fulfills all service requirements and other
                  conditions for receipt of such rights.

         11.10. EVIDENCE. Evidence required of anyone under the Plan may be 
by certificate, affidavit, document or other information which the person 
acting on it considers pertinent and reliable, and signed, made or presented 
by the proper party or parties.

         11.11. GENDER AND NUMBER. Where the context admits, words in one 
gender shall include the other gender, words in the singular shall include 
the plural and the plural shall include the singular.


                                       -9-

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         12.  CHANGE IN CONTROL.

         12.1.  ACCELERATION. Except as otherwise provided in the Plan or the 
Agreement reflecting the applicable Award, upon the occurrence of a Change in 
Control:

         (a)      All outstanding Options (regardless of whether in tandem with
                  Stock Appreciation Rights) and Stock Appreciation Rights
                  (regardless of whether in tandem with Options) shall become
                  fully exercisable.

         (b)      All Stock Awards shall become fully vested.

         (c)      Performance Units may be paid out in such manner and amounts
                  as determined by the Committee.

         12.2. DEFINITION OF CHANGE IN CONTROL. For purposes of the Plan, the 
term "Change in Control" means a change in the beneficial ownership of the 
Company's voting stock or a change in the composition of the Board which 
occurs as follows:

         (a)      any "Person" (as such term is used in Section 13(d) and 
                  14(d)(2) of the Exchange Act), other than Vysis, any
                  entity owned, directly or indirectly, by the stockholders
                  of Vysis in substantially the same proportions as their
                  ownership of stock of Vysis, and any trustee or other
                  fiduciary holding securities under an employee benefit
                  plan of Vysis or its subsidiaries or such proportionately
                  owned corporation) becomes through acquisitions of
                  securities of Vysis after the Effective Date of the Plan,
                  the "beneficial owner" (as defined in Rule 13d-3 promulgated
                  under the Exchange Act), directly or indirectly, of
                  securities of Vysis representing 40% or more of the 
                  combined voting power of Vysis' then outstanding securities
                  having the right to vote for the election of directors;

         (b)      the stockholders of Vysis approve a merger or consolidation
                  of Vysis with any other corporation, other than (A) a
                  merger or consolidation which would result in the voting
                  securities of Vysis outstanding immediately prior thereto
                  continuing to represent (either by remaining outstanding
                  or by being converted into voting securities of the
                  surviving entity) more than 50% of the combined voting
                  power of the voting securities of Vysis or such surviving
                  entity outstanding immediately after such merger or
                  consolidation, or (B) a merger or consolidation effected to
                  implement a recapitalization of Vysis (or similar transaction)
                  in which no Person acquires more than 15% of Vysis' then
                  outstanding securities having the right to vote for the
                  election of directors;

         (c)      the stockholders of Vysis approve a plan of complete
                  liquidation of Vysis or an agreement for the sale or
                  disposition by Vysis of all or substantially all of Vysis'
                  assets (or any transaction having a similar effect); or


                                       -10-

<PAGE>


         (d)      during any 24 month period, individuals who at the 
                  beginning of such period constitute the board of directors 
                  of Vysis, and any new director (other than a director 
                  designated by a Person who has entered into an agreement
                  with Vysis to effect a transaction described in paragraph (a),
                  (b) or (c) of this subsection 12.2) whose election by the
                  board or nomination for election by Vysis' stockholders
                  was approved by a vote of at least two-thirds of the
                  directors then still in office who either were directors
                  at the beginning of the period or whose election or 
                  nomination for election was previously so approved,
                  cease for any reason to constitute at least a majority
                  thereof.

13.      AMENDMENT AND TERMINATION.

         The Board may, at any time, amend or terminate the Plan, provided 
that, subject to subsection 5.4 (relating to certain adjustments to shares), 
no amendment or termination may materially adversely affect the rights of any 
Participant or beneficiary under any Award made under the Plan prior to the 
date such amendment is adopted by the Board. Notwithstanding the foregoing or 
any other provision of the Plan or any Award agreement, the Board or the 
Committee may amend the Plan or the terms of any Award to the extent it deems 
necessary to preserve pooling-of-interest accounting treatment for any 
transaction which is intended to be accounted for through such accounting 
method.




                                       -11-