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                            REGISTRATION RIGHTS AGREEMENT


     THIS AGREEMENT, made as of February 5, 1998, is by and between Vysis,
Inc., a Delaware corporation (the "Company"), and Amoco Technology Company, a
Delaware corporation (the "Stockholder").

     This Agreement is made in connection with the registration for sale to
the public of shares of common stock, $.001 par value, of the Company (the
"Common Stock") pursuant to a registration statement on Form S-1 and any
amendments thereto (the "Registration Statement") originally filed with the
Securities and Exchange Commission (the "Commission") on October 17, 1997
(File No. 333-38109) (the "Initial Public Offering").

     Prior to the Initial Public Offering, the Stockholder owned
approximately 100% of the issued and outstanding shares of common stock of
the Company and upon consummation of the Initial Public Offering the
Stockholder will own approximately 63% of the outstanding Common Stock.

     THE PARTIES HERETO AGREE AS FOLLOWS:

     1.   DEFINITIONS.  As used in this Agreement, the following capitalized
terms shall have the following respective meanings:

          AFFILIATE -- Of any Person is any Person which, directly or
indirectly, controls or is controlled by or is under common control with,
such Person.  A Person shall be deemed to be "controlled by" any other Person
if such other Person possesses, directly or indirectly, power (i) to vote 10%
or more of the securities having ordinary voting power for the election of
managing general partners or directors (or Persons holding equivalent
positions) of such Person (or, at the time extraordinary voting powers are
available, to vote 10% or more of the securities having extraordinary voting
power); or (ii) to direct or cause the direction of the management and
policies of such Person whether by contract or otherwise.

          EXCHANGE ACT - The Securities Exchange Act of 1934, as amended, or
any similar federal statute then in effect, and a reference to a particular
section thereof shall be deemed to include a reference to the comparable
section, if any, of any such similar federal statute.

          HOLDER - The Stockholder and any Person to whom it has assigned
rights hereunder as permitted by Section 10(c).

          PERSON - Any individual, partnership, joint venture, corporation,
trust, unincorporated organization or government or any department or agency
thereof.

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          REGISTRABLE SECURITIES - The Common Stock owned by the Stockholder
on the date hereof, Common Stock issuable to the Stockholder upon conversion
of the Company's outstanding shares of Series A Preferred Stock or Series B
Preferred Stock and any Common Stock or other securities which may be issued
or distributed in respect thereof by way of or in connection with a stock
dividend or stock split or other distribution, recapitalization,
reclassification, combination of shares, merger, consolidation or other
reorganization.  As to any particular Registrable Securities, such
Registrable Securities shall cease to be Registrable Securities when they
cease to be owned by a Holder.

          SECURITIES ACT - The Securities Act of 1933, as amended, or any
similar federal statute then in effect, and a reference to a particular
section thereof shall be deemed to include a reference to the comparable
section, if any, of any such similar federal statute.

          SHELF REGISTRATION STATEMENT - A registration statement on Form S-3
filed pursuant to Rule 415 under the Securities Act.

     2.(a) DEMAND REGISTRATION.  In the event that following 180 days after
the effective date of the Registration Statement any Holder or Holders desire
to sell shares of Registrable Securities owned by such Holder or Holders then
upon the written request of any Holder or Holders requesting that the Company
effect the registration under the Securities Act of all or part of such
Holder's or Holders' Registrable Securities and specifying the intended
method of disposition thereof, but subject to the limitations set forth
herein, the Company will promptly give written notice of such requested
registration to all other Holders of Registrable Securities, and the Company
shall file with the Commission as promptly as practicable after sending such
notice, and use its best efforts to cause to become effective, a registration
statement under the Securities Act registering the offering and sale of:

          (i) the Registrable Securities which the Company has been so requested
     to register by such Holder or Holders; and

          (ii) all other Registrable Securities which the Company has been
     requested to register by any other Holder thereof by written request given
     to the Company within 15 days after the giving of such written notice by
     the Company (which request shall specify the intended method of disposition
     of such Registrable Securities),

all to the extent necessary to permit the disposition (in accordance with the
intended method thereof as aforesaid) of the

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Registrable Securities so to be registered; PROVIDED, that the Company shall
not be obligated to file a registration statement relating to any
registration request under this Section 2(a) (A) unless the aggregate
requests by the Holder or Holders for such registration cover not less than
an aggregate of 1,000,000 shares (adjusted for any stock splits, reverse
stock splits or combination of shares) or (B) with respect to more than one
such registration per calendar year; provided that a request may cover fewer
than 1,000,000 shares (but not less than 500,000 shares) if the total number
of shares of Registrable Securities then outstanding is less than 1,000,000.

     A request for registration under this Section 2(a) shall not be counted
for purposes of the foregoing limitation (i) unless a registration statement
has become effective and has been kept continuously effective for the period
required under Section 4(b), (ii) if after it has become effective, use of
such registration statement is suspended by any stop order, injunction or
other order or requirement of the Commission or other governmental agency or
court, (iii) if no Registrable Securities are sold within the period during
which the registration statement has been kept continuously effective as
required under Section 4(b).

     A Holder may, in connection with a request for registration under this
Section 2(a), specify that the Registrable Securities are to be sold on a
delayed or continuous basis, in which case the Company shall file a Shelf
Registration Statement with respect thereto; provided, that each of the
following conditions has been satisfied: (i) the Company is eligible to file
a registration statement on Form S-3, (ii) a period of six years has elapsed
since the effective date of the Registration Statement  and (iii) the total
number of Registrable Securities outstanding constitutes 30% or less of the
total number of shares of Common Stock outstanding.

     (b) PRIORITY IN REQUESTED REGISTRATIONS.  If a requested registration
pursuant to this Section 2 involves an underwritten offering and the managing
underwriter advises the Company in writing that, in its opinion, the number
of securities requested to be included in such registration (including
securities of the Company which are not Registrable Securities) exceeds the
number which can be sold in such offering, the Company will include in such
registration only the Registrable Securities requested to be included in such
registration.  In the event that the number of Registrable Securities
requested to be included in such registration exceeds the number which, in
the opinion of such managing underwriter, can be sold, the number of such
shall be allocated first to the Stockholder and its Affiliates, and then  pro
rata among all other requesting Holders on the basis of the

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relative number of shares of Registrable Securities originally requested to
be included by each such Holder.

     (c) LIMITATION ON REGISTRATION RIGHTS.

          (i) If a request for registration pursuant to Section 2(a) hereof is
     made within 30 days prior to the conclusion of the Company's then current
     fiscal year, or within 40 days after the end of a fiscal year, the Company
     shall not be required to file a registration statement until such time as
     the Company receives its audited financial statements for such fiscal year.

          (ii) The Company shall be entitled to postpone for a reasonable period
     of time (not to exceed 90 days, which may not thereafter be extended
     without the mutual agreement of the Company and the Holder or Holders
     requesting registration) the filing of any registration statement otherwise
     required to be prepared and filed by it pursuant to Section 2(a) hereof if,
     at the time it receives a request for such registration, (w) the Company is
     conducting or about to conduct an offering of any class of its securities
     and the Company is advised by the investment banker or financial advisor
     engaged by the Company to advise the Company thereon that such offering
     would be affected adversely by the registration so demanded and the Company
     shall have furnished to the Holder or Holders of Registrable Securities
     requesting such registration an Officers' Certificate to that effect,
     (x) the Company is in possession of material information that has not been
     disclosed to the public and the Company deems it advisable not to disclose
     such information in the registration statement, (y) the Company is engaged
     in any active program for repurchase of its Common Stock or (z) the board
     of directors of the Company shall determine in good faith that such
     offering will interfere with a pending or contemplated financing, merger,
     acquisition, sale of assets, recapitalization or other similar corporate
     action of the Company and the Company shall have furnished to the Holder or
     Holders of Registrable Securities requesting such registration an Officers'
     Certificate to that effect.  The Company may only exercise its right to
     postpone the filing of registration statement under this Section 2(c)(ii)
     once in any calendar year.  In the event of the exercise by the Company of
     such postponement right, it shall furnish the requesting Holders with an
     estimate as to when the circumstances permitting the Company to postpone
     such filing shall cease to exist and thereafter give the Holders prompt
     notice of such cessation.  After such period of postponement the Company
     shall effect such registration as promptly as practicable without further
     request from the Holder or Holders of Registrable Securities, unless such
     request has been withdrawn.

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          (iii) Except as otherwise provided herein, any request by a Holder or
     Holders for registration of Registrable Securities pursuant to Section 2(a)
     hereof, which is subsequently withdrawn prior to the registration statement
     becoming effective, shall not constitute a registration statement for
     purposes of determining the number of registrations to which the Holder of
     such Registrable Securities is entitled pursuant to Section 2(a); PROVIDED,
     HOWEVER, that the Holder of such Registrable Securities shall reimburse the
     Company for all expenses incurred, including, without limitation,
     reasonable fees and expenses of the Company's attorneys, accountants and
     investment bankers, in connection with the preparation and filing, if
     filed, of such registration statement, unless such withdrawal is the result
     of a postponement by the Company under Section 2(c)(ii).

     (d) In connection with any request for registration under this Section 2
involving an underwritten offering, the requesting Holders shall have the
right to select the underwriter or underwriters with the consent of the
Company, which consent shall not be unreasonably withheld.

     3.(a) INCIDENTAL REGISTRATION.  If the Company shall at any time propose
to file a registration statement under the Securities Act for an offering of
Common Stock of the Company for cash (other than an offering relating to (i)
a business combination that is to be filed on Form S-4 under the Securities
Act (or any successor form thereto) or (ii) an employee benefit plan or (iii)
securities of the Company convertible into Common Stock where no separate
consideration is received by the Company for such Common Stock), the Company
shall provide prompt written notice of such proposal to all Holders of
Registrable Securities of its intention to do so and of such Holders' rights
under this Section 3 and shall use its reasonable efforts to include such
number or amount of Registrable Securities in such registration statement,
which the Company has been so requested to register by the Holders thereof,
which request shall be made to the Company within 10 business days after the
Holder receives notice from the Company of such proposed registration;
PROVIDED, that (i) if, at any time after giving written notice of its
intention to register any securities and prior to the effective date of the
registration statement filed in connection with such registration, the
Company shall determine for any reason not to register such securities, the
Company may, at its election, give written notice of such determination to
each Holder of Registrable Securities and, thereupon, shall be relieved of
its obligation to register any Registrable Securities in connection with such
registration

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(but not from its obligation to pay the registration expenses referred to in
Section 5 incurred in connection therewith), and (ii) if such registration
involves an underwritten offering, all Holders of Registrable Securities
requesting to be included in the Company's registration must sell their
Registrable Securities to the underwriters selected by the Company on the
same terms and conditions as apply to the Company, with such differences,
including any with respect to indemnification and liability insurance, as may
be customary or appropriate in combined primary and secondary offerings.  The
Holders shall have the right to revoke their election to have their shares
included in such registration at any time prior to the filing of the
registration statement.

     (b) PRIORITY IN INCIDENTAL REGISTRATIONS.  If a registration pursuant to
this Section 3 involves an underwritten offering and the managing underwriter
advises the Company in writing that, in its opinion, the number of securities
to be included in such registration exceeds the number which can be sold in
such offering, so as to be likely to have a significant adverse effect on
such offering as contemplated by the Company (including the price, timing or
distribution of which the Company proposes to sell such securities), then the
Company will include in such registration (i) first, 100% of the securities
the Company proposes to sell, (ii) second, to the extent of the number of
Registrable Securities requested to be included in such registration which,
in the opinion of such managing underwriter, can be sold without having the
significant adverse effect referred to above, the number of Registrable
Securities which the Holders have requested to be included in such
registration, such amount to be allocated first to the Stockholder and its
Affiliates, and then pro rata among all requesting Holders on the basis of
the relative number of shares of Registrable Securities initially requested
to be included by each such Holder.

     4. REGISTRATION PROCEDURES.  Whenever a Holder or Holders have requested
that any Registrable Securities be registered pursuant to this Agreement, the
Company will use its best efforts to effect the registration and the sale of
such Registrable Securities in accordance with the intended method of
disposition thereof, and pursuant thereto the Company will as expeditiously
as possible:

          (a) prepare and file with the Commission a registration statement with
     respect to such Registrable Securities (which shall be effected within 30
     days of a request in the case of a registration under Section 2(a)) and use
     its best efforts to cause such registration statement to become effective
     (provided that before filing a registration statement or prospectus or any
     amendments or supplements thereto, the Company will furnish to the counsel

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     selected by the Holders of a majority of the Registrable Securities covered
     by such registration statement copies of all such documents proposed to be
     filed, which documents shall be subject to review of such counsel;

          (b) prepare and file with the Commission such amendments and
     supplements to such registration statement and the prospectus used in
     connection therewith as may be necessary to keep such registration
     statement effective for such period as is necessary to complete the
     disposition of all securities covered by such registration statement during
     such period in accordance with the intended methods of disposition by the
     seller or sellers thereof set forth in such registration statement;
     PROVIDED, HOWEVER, that such period shall not exceed 90 days unless the
     registration statement is a Shelf Registration Statement;

          (c) furnish to each seller of Registrable Securities such number of
     copies of such registration statement, each amendment and supplement
     thereto, the prospectus included in such registration statement (including
     each preliminary prospectus) and such other documents as such seller may
     reasonably request in order to facilitate the disposition of the
     Registrable Securities owned by such seller;

          (d) use its best efforts to register or qualify such Registrable
     Securities under such other securities or blue sky laws of such
     jurisdictions as any seller reasonably requests and do any and all other
     acts and things that may be reasonably necessary or advisable to enable
     such seller to consummate the disposition in such jurisdictions of the
     Registrable Securities owned by such seller (provided that the Company will
     not be required to (i) qualify generally to do business in any jurisdiction
     where it would not otherwise be required to qualify but for this
     subparagraph, (ii) subject itself to taxation in any such jurisdiction or
     (iii) consent to general service of process in any such jurisdiction);

          (e) notify each seller of such Registrable Securities, at any time
     when a prospectus relating thereto is required to be delivered under the
     Securities Act,(i) of the occurrence of any event as a result of which the
     prospectus included in such registration statement contains an untrue
     statement of a material fact or omits any fact necessary to make the
     statements therein, in light of the circumstances under which made, not
     misleading, and at the request of any such seller, the Company will prepare
     a supplement or amendment to such prospectus so that, as thereafter
     delivered to the purchasers of such Registrable Securities, such prospectus
     will not contain an untrue statement of a

                                    -7-
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     material fact or omit to state any fact necessary to make the statements
     therein, in light of the circumstances under which made, not misleading;
     or (ii) of the issuance by the Commission of any stop order suspending
     the effectiveness of the registration statement or of any order
     preventing or suspending the use of any preliminary prospectus, or of
     the suspension of the qualification of the registration statement for
     offering or sale in any jurisdiction, or of the institution or
     threatening of any proceedings for any of such purposes; PROVIDED,
     HOWEVER, that the Company shall not be required to notify a seller of
     Registrable Securities of the occurrence of any event described in
     clause (i) hereof that relates to a prospectus contained in a Shelf
     Registration Statement unless within the 30 days prior thereto the
     seller has given the Company notice of its intention to offer or sell
     Registrable Securities pursuant to Section 5(e) below;

          (f) cause all such Registrable Securities to be listed on each
     securities exchange on which securities issued by the Company that are of
     the same class as the Registrable Securities are then listed;

          (g) provide a transfer agent and registrar for all such Registrable
     Securities not later than the effective date of such registration
     statement;

          (h) make available for inspection by any seller of Registrable
     Securities, any underwriter participating in any disposition pursuant to
     such registration statement and any attorney, accountant or other agent
     retained by any such seller or underwriter all financial and other records,
     pertinent corporate documents and properties of the Company, and cause the
     Company's officers, directors, employees and independent certified public
     accountants to supply all information reasonably requested by any such
     seller, underwriter, attorney, accountant or agent in connection with such
     registration statement;

          (i) use its best efforts to cause such Registrable Securities covered
     by such registration statement to be registered with or approved by such
     other governmental agencies or authorities as may be necessary to enable
     the sellers thereof to consummate the disposition of such Registrable
     Securities;

          (j) obtain a "cold comfort" letter from the Company's independent
     public accountants in customary form and covering such matters of the type
     customarily covered by "cold comfort" letters as the seller or sellers of a
     majority of the Registrable Securities being sold reasonably request;

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<PAGE>

          (k) if underwriters are engaged by the Company in connection with any
     registration referred to in this Agreement (such underwriters shall be
     reasonably satisfactory to the Holders of a majority of the Registrable
     Securities covered by such registration), the Company shall provide
     indemnification, representations, covenants, opinions and other assurance
     to the underwriters in form and substance reasonably satisfactory to such
     underwriters; and

          (l) enter into such customary agreements (including underwriting
     agreements in customary form) and take all such other actions as the
     Holders of a majority of the Registrable Securities being sold or the
     underwriters, if any, reasonably request in order to expedite or facilitate
     the disposition of such Registrable Securities.

          (m) obtain an opinion of outside counsel (or inside counsel if
     satisfactory to each underwriter) for the Company covering such matters of
     the type customarily covered in opinions of issuer's counsel as the seller
     or sellers of a majority of the Registrable Securities being sold
     reasonably request;

          (n) file the reports required by the Exchange Act for companies
     registered under such act and otherwise comply with all applicable rules
     and regulations of the Commission;

          (o) keep the sellers advised as to the initiation and progress of any
     demand or other registration; and

          (p) promptly deliver to the Holders copies of all public announcements
     made by the Company regarding disposition, acquisitions or other material
     transactions involving the Company.

     5. HOLDERS' OBLIGATIONS IN REGISTRATION.

          (a) Each Holder agrees, that, upon receipt of notice of an event
     described in Section 4(e) above, such Holders will immediately discontinue
     disposition of the Registrable Securities until such Holder's receipt of
     the copies of the supplemented or amended prospectus contemplated by
     Section 4(e) or until it is advised in writing by the Company that the use
     of the prospectus may be resumed, and has received copies of any additional
     or supplemental filings which are incorporated by reference in the
     prospectus.  If so directed by the Company, such Holder will, or will
     request the managing underwriter or agent, if

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     any, to deliver to the Company at the Company's expense all copies
     (other than permanent file copies) then in such Holder's possession, of
     the prospectus covering such Registrable Securities current at the time
     of receipt of such notice.

          (b) In respect of a registration pursuant to this Agreement, each
     Holder of Registrable Securities covered by a registration statement shall
     advise the Company immediately if such Holder knows or becomes aware of any
     matter which such Holder believes may result in the inclusion in a
     prospectus contained in such registration statement of an untrue statement
     of a material fact or the omission of a material fact required to be stated
     therein or necessary to make the statements therein not misleading, and
     shall promptly notify the Company and assist the Company in preparation and
     filing with the Commission of any such amendments or supplements to said
     registration statement that may be necessary or appropriate to permit the
     prospectus included therein to be used under the Securities Act during the
     period during which the prospectus must be delivered in connection with the
     offering and sale of the Registrable Securities.

          (c) The Company may require each Holder of Registrable Securities as
     to which any registration is being effected to furnish to the Company such
     information regarding the distribution of such Registrable Securities and
     such other information relating to the Holder and its ownership of
     Registrable Securities as the Company may from time to time reasonably
     request and each Holder agrees to furnish the Company with such information
     and to cooperate with the Company as necessary to enable the Company to
     comply with the provisions of this Agreement.

          (d) In the case of any underwritten public offering by the Company of
     any shares of Common Stock or securities convertible into shares of Common
     Stock, each Holder of Registrable Securities agrees, if and to the extent
     requested in writing by the managing underwriter of such offering, not to
     effect any public sale or distribution of the Common Stock of the Company
     (except as part of such underwritten offering), during the period ending on
     the earlier of (i) 90 days after the effective date of the registration
     statement relating to such underwritten public offering and (ii) the date
     such sale or distribution is permitted by such managing underwriter.

          (e)In the event that a Shelf Registration Statement has been filed and
     declared effective with respect to any Registrable Securities, the Holder
     of such Registrable

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     Securities agrees to notify the Company of any proposed offer or sale
     thereof at least two business days prior to the proposed offer or sale.
     Such notice shall include such information relating to the Holder and
     the proposed distribution of Registrable Securities by the Holder as
     shall be required to be included in the prospectus, to the extent such
     information has not already been included therein.  If within such two
     business day period the Company advises the Holder furnishing such
     notice that the Company is in possession of material information that
     has not been disclosed to the public and the Company deems it advisable
     not to disclose such information in the prospectus, then the Holder
     furnishing such notice shall postpone the contemplated offering or sale
     until the earlier to occur of (i) the date as of which the Company is no
     longer in possession of such undisclosed material information (notice of
     which the Company agrees to promptly furnish to the Holder)or (ii) the
     date which is 30 days following the receipt by the Company of the notice
     of proposed offer or sale.  A Holder furnishing a notice of proposed
     offer or sale to the Company pursuant to this Section 5(e) shall
     promptly notify the Company of the termination of such offering or
     completion of such sale.

     6. REGISTRATION EXPENSES.  All expenses incidental to the Company's
performance of or compliance with this Agreement, including, without limitation,
all registration and filing fees, fees and expenses of compliance with
securities or blue sky laws, printing expenses, messenger and delivery expenses,
and fees and disbursements of counsel for the Company and all independent
certified public accountants, underwriters (excluding discounts and commissions)
and other persons retained by the Company, including, without limitation, all
salaries and expenses of the Company's officers and employees performing legal
or accounting duties, the expense of any annual audit or quarterly review, the
expense of any liability insurance and the expenses and fees for listing the
securities to be registered on each securities exchange on which securities
issued by the Company that are of the same class as the Registrable Securities
are then listed will be borne by the Company, except that underwriting discounts
and commissions relating to the sale of Registrable Securities will be the
responsibility of each seller, and each seller shall be responsible for all fees
and disbursements of their own counsel.

     7. TERM.  This Agreement shall terminate at such time as the shares of
Registrable Securities owned by the Holders of Registrable Securities constitute
less than 5% of the issued and outstanding shares of Common Stock of the
Company.

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     8. INDEMNIFICATION.  The provisions of this Section 8 shall be applicable
in respect of each registration pursuant to this Agreement.

     (a)  The Company shall hold harmless and indemnify each Holder of
Registrable Securities, any underwriter or agent participating in an offering
and their respective Affiliates (including any director, officer, employee,
agent or controlling Person of any of the foregoing), from and against all
losses, claims, damages, liabilities and expenses (including reasonable
attorneys' fees and expenses of investigation) incurred by such indemnified
party pursuant to any actual or threatened third-party action, suit, proceeding
or investigation (including reasonable attorneys' fees and expenses of
investigation) arising out of or based upon any untrue or alleged untrue
statement of material fact contained in any registration statement, any
amendment or supplement thereto, any prospectus or preliminary prospectus or any
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein (in the case of a
prospectus, in light of the circumstances under which they were made) not
misleading, except insofar as the same arise out of or are based upon any such
untrue statement or omission based upon information with respect to such Holder
furnished in writing to the Company by such Holder expressly for use therein.

     (b) In connection with any registration statement in which a Holder of
Registrable Securities is participating, each such Holder will furnish to the
Company in writing such information, as the Company reasonably requests for use
in connection with any such registration statement or prospectus, and shall
severally and not jointly hold harmless and indemnify each other Holder of
Registrable Securities, any underwriter or agent participating in an offering,
the Company and its Affiliates (including any director, officer, employee,
agent, or controlling Person of each of the foregoing) from and against any
losses, claims, damages, liabilities and expenses (including reasonable
attorneys' fees and reasonable expenses of investigation) incurred by such
indemnified party pursuant to any actual or threatened third-party action, suit,
proceeding or investigation (including reasonable attorneys' fees and expenses
of investigation) arising out of or based upon any untrue or alleged untrue
statement of a material fact contained in any registration statement, any
amendment or supplement thereto, any prospectus or preliminary prospectus or any
omission or alleged omission of a material fact required to be stated therein or
necessary to make the statements therein (in case of a prospectus, in the light
of the circumstances under which they were made) not misleading, to the extent,
but only to the extent, that such untrue statement or omission is contained in
or failed to be contained in any information with respect to such Holder
furnished in writing by

                                      -12-
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such Holder specifically for inclusion in any prospectus or registration
statement; PROVIDED, HOWEVER, that the liability of such indemnifying party
under this Section 8(b) shall be limited to the amount of net proceeds
received by such indemnifying party in the offering giving rise to such
liability.

     (c) The obligation of the Company under Section 8(a) and of the Holders
of Registrable Securities under Section 8(b) to hold harmless and indemnify
any underwriter or agent who participates in an offering or any of their
respective Affiliates shall be conditioned on the underwriting or agency
agreement containing an agreement by such underwriter or agent to hold
harmless and indemnify each of the Company, the Holders of Registrable
Securities participating in the offering, and their respective Affiliates
(including any director, officer, employee, agent, or controlling Person of
each of the foregoing) from and against any losses, claims, damages,
liabilities and expenses (including reasonable attorneys' fees and expenses
of investigation) incurred by such indemnified parties pursuant to any actual
or threatened third-party action, suit, proceeding or investigation
(including reasonable attorneys' fees and expenses of investigation) arising
out of or based upon any untrue or alleged untrue statement of a material
fact contained in any registration statement, any amendment or supplement
thereof, any prospectus or preliminary prospectus or any omission or alleged
omission of a material fact required to be stated therein or necessary to
make the statements therein (in the case of a prospectus, in light of the
circumstances under which they were made) not misleading, to the extent, but
only to the extent, that such untrue statement or omission is contained or
failed to be contained in any information with respect to such underwriter or
agent furnished in writing by such underwriter or agent specifically for
inclusion in any prospectus or registration statement.

     (d) The indemnity provisions in Sections 8(a) and 8(b) above are subject
to the condition that, insofar as they relate to any untrue statement (or
alleged untrue statement) or omission (or alleged omission) made in a
preliminary prospectus or prospectus but eliminated or remedied in any
amended prospectus, such indemnity provisions shall not inure to the benefit
of any indemnified Person, if the Company has previously and in a timely
manner delivered sufficient copies of such amended prospectus to such
indemnified Person and if a copy of such amended prospectus required to be
sent or given in accordance with any applicable law or regulation was not
furnished by such indemnified Person to the person asserting the loss,
liability, claim or damage.

     (e) Promptly after receipt by an indemnified party under this Section 8
of any notice of the commencement of any lawsuit or other proceeding or
investigation thereof, such indemnified party will, if a claim in respect
thereof is to be made against

                                    -13-
<PAGE>

the indemnifying parties hereunder, notify in writing the indemnifying
parties of the commencement thereof; but the omission so to notify the
indemnifying parties will not relieve the indemnifying parties from any
liability which they may have to any indemnified party, unless such failure
to notify is materially prejudicial to the indemnifying parties and
materially increases their risk of loss.  In case any such lawsuit or other
proceeding or investigation shall be brought against any indemnified party
and such indemnified party shall notify the indemnifying parties of the
commencement thereof, the indemnifying parties shall be entitled to
participate therein and, unless in the opinion of counsel to the indemnified
party a conflict of interest between such indemnified and indemnifying
parties may exist in respect of such claim, to the extent that it shall wish,
to assume the defense thereof, with counsel reasonably satisfactory to such
indemnified party (who shall not, except with the consent of the indemnified
party, be counsel to the indemnifying parties in such action).  In any such
proceeding, any indemnified party shall have the right to retain its own
counsel, but the fees and expenses of such counsel shall be at the expense of
such indemnified party unless (i) the indemnifying party and the indemnified
party shall have mutually agreed to the retention of such counsel,(ii) the
indemnifying parties shall have failed to assume the defense of such action
or proceeding or shall have failed to employ counsel reasonably satisfactory
to such indemnified party in any action or proceeding; or (iii) the named
parties (including any impleaded parties) to any such action or proceeding
include both such indemnified party and the indemnifying parties, and such
indemnified party shall have been advised by counsel in writing (with a copy
to the indemnifying parties) that there may be one or more defenses available
to such indemnified party or other indemnified parties or other indemnified
parties which are different from or additional to those available to the
indemnifying parties, then, such separate counsel shall be at the expense of
the indemnifying parties and the indemnifying parties shall not have the
right to assume the defense of such action or proceeding on behalf of such
indemnified person.   After notice from the indemnifying parties to such
indemnified party of their election so to assume the defense thereof, and
provided that the exception in the foregoing sentence does not apply, the
indemnifying parties shall not be liable to such indemnified party under
these indemnification provisions for any legal expenses of other counsel or
any other expenses, in each case subsequently incurred by such indemnified
party, in connection with the defense thereof other than reasonable costs of
investigation.  In any event, unless there exists a conflict among
indemnified parties, the indemnifying parties shall not, in connection with
any one such action or proceeding or separate but substantially similar or
related actions or proceedings in the same jurisdiction arising out of the
same general allegations or

                                    -14-
<PAGE>

circumstances, be liable for the fees and expenses of more than one separate
firm of attorneys at any time for all such indemnified parties.  No
indemnifying party shall, without the prior written consent of the
indemnified party, effect any settlement of any pending or threatened
proceeding in respect of which any indemnified party is or could have been a
party and indemnity could have been sought hereunder by such indemnified
party unless such settlement includes an unconditional release of such
indemnified party from all liability on claims that are the subject matter of
such proceeding.  The indemnifying parties shall not be subject to any
liability for any settlement made without their consent.

     (f)  In order to provide for the just and equitable contribution in
circumstances under which the indemnity provided for in this Section 8 is for
any reason held to be unenforceable by the indemnified parties though
applicable in accordance with its terms, each applicable indemnifying party,
in lieu of indemnifying such indemnified party, shall contribute to the
amount paid or payable by such indemnified party as a result of any losses,
claims, damages, liabilities or expenses of a nature contemplated by such
indemnity in such proportion as is appropriate to reflect not only the
relative benefits received by the indemnifying parties and the indemnified
parties, but also to reflect the relative fault of the indemnifying and
indemnified parties in connection with the statements or omissions which
resulted in such losses, claims, damages, liabilities or expenses, as well as
any other relevant equitable considerations; PROVIDED, HOWEVER, that no
Person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution from any
Person who was not guilty of such fraudulent misrepresentation.
Notwithstanding anything in this subsection (f) to the contrary, no Holder
shall be required to contribute any amount in excess of the net proceeds
received by such Holder from the offering to which the losses, claims,
damages, liabilities or expenses relate.

     The relative fault of such indemnifying and indemnified parties shall be
determined by reference to, among other things, whether any untrue or alleged
untrue statement of a material fact, or omission or alleged omission to state
a material fact, has been made by, or relates to information supplied by,
such indemnifying party or indemnified parties and the parties' relative
intent, knowledge, access to information and opportunity to correct or
prevent such statement or omission.  The amount paid or payable by a party as
a result of the losses, claims, damages, liabilities and expenses referred to
above shall be deemed to include any legal or other fees or expenses incurred
by such party in connection with investigating or defending such claim

                                   -15-
<PAGE>

     9. PARTICIPATION IN UNDERWRITTEN REGISTRATIONS.  No person may
participate in any registration hereunder that is underwritten unless such
person (a) agrees to sell such person's securities on the basis provided in
any underwriting arrangements approved by the person or persons entitled
hereunder to approve such arrangements and (b) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents required under the terms of such underwriting arrangements.

     10. MISCELLANEOUS.

     (a) REMEDIES.  Any person having rights under any provision of this
Agreement will be entitled to enforce such rights specifically, to recover
damages caused by reason of any breach of any provision of this Agreement and
to exercise all other rights granted by law.

     (b) AMENDMENT AND WAIVERS.  The provisions of this Agreement may be
amended and the Company may take any action herein prohibited, or omit to
perform any act herein required to be performed by it, only if the Company
has obtained the written consent of the Stockholder and its Affiliates (to
the extent they are holders of Registrable Securities) and of Holders of at
least 50% of the Registrable Securities held by any other Persons.

     (c) SUCCESSORS AND ASSIGNS.  All covenants and agreements in this
Agreement by or on behalf of any of the parties hereto will bind and inure to
the benefit of the respective successors and permitted assigns of the parties
hereto whether so expressed or not.  A Holder shall be permitted to assign
its rights hereunder to any Person to whom it transfers any Registrable
Securities in a transaction not involving any public offering, provided that
(A)(i) the number of Registrable Securities so transferred is not less than
1,000,000 shares (adjusted for any stock split, reverse stock split or
combination of shares) and (ii) the assignee agrees with the Company in
writing to be bound by the provisions of this Agreement or (B) such Person is
an Affiliate of Stockholder.

     (d) 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
prohibited by or invalid under applicable law, such provision will be
ineffective only to the extent of such prohibition or invalidity, without
invalidating the remainder of this Agreement.

     (e) COUNTERPARTS.  This Agreement may be executed in two or more
counterparts, any one of which need not contain the signatures

                                 -16-
<PAGE>

of more than one party, but all such counterparts taken together will
constitute one and the same Agreement.

     (f) DESCRIPTIVE HEADINGS.  The descriptive headings of this Agreement
are inserted for convenience only and do not constitute a part of this
Agreement.

     (g) GOVERNING LAW.  The General Corporation Law of Delaware will govern
all issues concerning the relative rights of the Company and the Holders of
Registrable Securities.  All other questions concerning the construction,
validity and interpretation of this Agreement and the exhibits and schedules
hereto will be governed by the internal law, and not the law of conflicts, of
the State of Delaware.

     (h) NOTICES.  All notices, demands or other communications to be given
or delivered under or by reason of the provisions of this Agreement will be
in writing and will be deemed to have been given when delivered personally or
two days after deposit in the mail, certified or registered mail, return
receipt requested and postage prepaid, to the recipient.  Such notices,
demands and other communication will be sent to the Stockholder initially as
set forth below and to each other Holder of Registrable Securities at such
Holder's address as it appears in the records of the Company (unless
otherwise indicated by any such Holder to the Company in writing) and to the
Company at its principal executive offices.

     For ATC:       3100 Woodcreek Drive
                    Downers Grove, Illinois  60515
                    Attn: President

with a copy to:     Amoco Corporation
                    200 East Randolph Drive
                    Chicago, Illinois  60601
                    Attn:  General Attorney --
                             Corporate Law Department





                                         -17-

<PAGE>


     IN WITNESS WHEREOF, the parties have executed this Agreement as of the date
first written above.

                                             VYSIS, INC.


                                             By: /s/ John L. Bishop
                                                 -----------------------

                                                  Name: John L. Bishop
                                                        ----------------
                                                  Title: President & CEO
                                                         ---------------


                                              AMOCO TECHNOLOGY COMPANY


                                             By: /s/ Robert C. Carr
                                                 -----------------------

                                                  Name: Robert C. Carr
                                                        ----------------
                                                  Title: President
                                                         ---------------











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