Document:

<PAGE>
CERTAIN MATERIAL (INDICATED BY AN ASTERISK) HAS BEEN OMITTED FROM THIS DOCUMENT
PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT. THE OMITTED MATERIAL HAS BEEN
FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                                                   EXHIBIT 10.23

               AMENDMENT TO THE LICENSE AGREEMENT BY AND BETWEEN
                   GEN-PROBE INCORPORATED, BIOANALYSIS, LTD.
                AND THE UNIVERSITY OF WALES COLLEGE OF MEDICINE
                             DATED JANUARY 21, 1986

     This Agreement is entered into as of this 11th day of May, 1989, by and
between Gen-Probe Incorporated, 9880 Campus Point Drive, San Diego, California
92121 ("Gen-Probe"), Bioanalysis, Ltd., P.O. Box 130, Cardiff CF4 4YL, United
Kingdom ("Bioanalysis"), and the University of Wales College of Medicine,
located at Heath Park, Cardiff CF44XN, United Kingdom ("UWCM").

     WHEREAS, Gen-Probe, Bioanalysis and UWCM are parties to a License
Agreement dated January 21, 1986, (the "Agreement"); and

     WHEREAS, the parties desire to make certain modifications to the Agreement;

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
set forth herein and other good and valuable consideration, the receipt of
which is hereby acknowledged, the parties hereby agree as follows:

     1.   Article 1, Subpart G of the Agreement shall be amended to read as
follows:

[***]

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

<PAGE>
[***]

     IN WITNESS WHEREOF, Gen-Probe, Bioanalysis and UWCM have duly executed
this Amendment on the dates indicated below.

<Table>
<Caption>
GEN-PROBE INCORPORATED                          BIOANALYSIS, LTD.
<S>                                      <C>
By:  /s/                                 By: /s/
    --------------------------               -------------------------
Title: President & CEO                   Title: Director
       -----------------------                  ----------------------

Date: 5/17/89                            Date: 17/5/89
      ------------------------                 -----------------------

UNIVERSITY OF WALES COLLEGE
  OF MEDICINE

By: /s/
    --------------------------

Title: DEPUTY REGISTRAR
       -----------------------

Date:  18 May 1989
      ------------------------
</Table>

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                       2<PAGE>
CERTAIN MATERIAL (INDICATED BY AN ASTERISK) HAS BEEN OMITTED FROM THIS DOCUMENT
PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT. THE OMITTED MATERIAL HAS BEEN
FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                                                   EXHIBIT 10.24

          AMENDMENT TO THE LICENSE AGREEMENT BY AND BETWEEN GEN-PROBE
         INCORPORATED, BIOANALYSIS LIMITED AND THE UNIVERSITY OF WALES
                   COLLEGE OF MEDICINE DATED JANUARY 21, 1986

This Agreement is entered into as of this 19th day of November, 1998 by and
between Gen-Probe Incorporated, 10210 Genetic Center Drive, San Diego,
California 92121 ("Gen-Probe"), Bioanalysis Limited, 5 Chiltern Close, Cardiff
Industrial Park, Cardiff CF4 5DL, United Kingdom ("Bioanalysis") and the
University of Wales College of Medicine, Heath Park, Cardiff CF4 4XN, United
Kingdom ("UWCM").

WHEREAS, Gen-Probe, Bioanalysis and UWCM are parties to a License Agreement
dated January 21, 1986 (the "Agreement"); and

WHEREAS, the parties desire to make certain modifications to the Agreement;

NOW, THEREFORE, the parties hereto agree as follows:

Article 1, Subpart G of the Agreement shall be amended to read as follows:

[***]

IN WITNESS WHEREOF, Gen-Probe, Bioanalysis and UWCM have duly executed this
Amendment on the dates indicated below.

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                  Page 1 of 2

<PAGE>

GEN-PROBE INCORPORATED                            BIOANALYSIS, LTD.

/s/ H.L. Nordhoff                                  /s/ JJ Woodhead
-----------------------------                     ------------------------------
Signature                                         Signature

     H.L. Nordhoff                                     JJ Woodhead
-----------------------------                     ------------------------------
Name                                              Name
        CEO                                               Director
-----------------------------                     ------------------------------
Title                                             Title
     11-24-98                                               11.20.1998
-----------------------------                     ------------------------------
Date                                              Date

UNIVERSITY OF WALES
COLLEGE OF MEDICINE

/s/     C.B. Turner
-----------------------------
Signature
     C.B. Turner
-----------------------------
Name
     Secretary
-----------------------------
Title
         7.12.98
-----------------------------
Date

                                  Page 2 of 2<PAGE>
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PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT. THE OMITTED MATERIAL HAS BEEN
FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                                                   EXHIBIT 10.25

                              NONEXCLUSIVE LICENSE
                          AGREEMENT UNDER VYSIS' [***]

THIS NONEXCLUSIVE LICENSE AGREEMENT (the "AGREEMENT") is made and is effective
the 22nd day of June, 1999 by and between Gen-Probe Incorporated ("GEN-PROBE"),
a Delaware corporation having its principal place of business in San Diego, CA
and Vysis, Inc. ("VYSIS"), a Delaware corporation having its principal place of
business in Downers Grove, IL WITNESSETH:

                                    RECITALS

WHEREAS, certain inventions generally characterized as [***];

WHEREAS, GEN-PROBE and VYSIS are engaged in litigation unrelated to VYSIS'
[***] and which litigation involves BP Amoco Corporation ("BP AMOCO"),
an Indiana Corporation having its principal place of business in Chicago, IL;

WHEREAS, GEN-PROBE has previously entered into alliances with Chiron Corporation
("CHIRON") for blood screening, with Bayer Corporation ("BAYER") for infectious
diseases and with [***] for infectious diseases;

WHEREAS, in partial fulfillment of a settlement of the litigation between
GEN-PROBE and VYSIS, GEN-PROBE desires to obtain certain license and rights
under the [***] for itself and certain options on behalf of its alliances with
CHIRON, BAYER and [***], and VYSIS desires and is able to grant certain license
and rights to GEN-PROBE for itself and options on behalf of its alliances;

GEN-PROBE and VYSIS agree hereto as follows:

                                 1. DEFINITIONS

1.1 The term [***] shall mean [***]. A Schedule of [***] is attached as Exhibit
1 hereto and incorporated herein by reference.

1.2 The term Licensed Method shall mean any method, the use or practice of which
would constitute, but for the license granted herein, an infringement of any
issued, Valid Claim within the [***].

*** Certain information on this page has been omitted and filed separately with
     the Commission. Confidential treatment has been requested with respect to
     the omitted portions.

                                  Page 1 of 12

<PAGE>
1.3 The term Valid Claim shall mean an issued claim of a [***] which has not
been ruled invalid by a court or an administrative agency of competent
jurisdiction from which all appeals have been exhausted.

1.4 The term Licensed Product shall mean any of the following:

      (a) Any product specifically intended for use in practicing a Licensed
      Method;

      (b) Any product which lacks substantial use other than in practicing a
      Licensed Method; and

      (c) Any product, the making, using, selling, offering for sale or
      importing of which, would constitute, but for the license granted herein,
      an infringement of any issued, Valid Claim within the [***].

1.5 The term GEN-PROBE/CHIRON ALLIANCE shall mean the current alliance for blood
screening entered into by GEN-PROBE and CHIRON by agreement dated June 11, 1998.
In the event that CHIRON assigns substantially all of its rights and obligations
under this blood screening alliance agreement to another party, the alliance
with such party shall assume the rights and obligations of CHIRON with respect
to the GEN-PROBE/CHIRON ALLIANCE.

1.6 The term GEN-PROBE/BAYER ALLIANCE shall mean the current alliance for
clinical diagnostics entered into by GEN-PROBE and CHIRON by agreement dated
June 11, 1998. CHIRON has assigned its rights and obligations under the clinical
diagnostics alliance agreement to Bayer. In the event that BAYER assigns
substantially all of its rights and obligations under the clinical diagnostics
alliance agreement to another party, the alliance with such party shall assume
the rights and obligations of BAYER with respect to the GEN-PROBE / BAYER
ALLIANCE.

1.7 The term End User Net Commercial Sales shall mean the total of the gross
invoice prices received by GEN-PROBE and any other [***] from end
users for Licensed Products or Licensed Methods less the sum of the following
actual and customary deductions where applicable: cash, trade, or quantity
discounts; sales, use, tariff, import/export duties or other excise taxes
imposed upon particular sales; transportation charges and allowances or credits
to customers because of rejections or returns. In the event Licensed Products or
Licensed Methods are sold to end users through distributors, the gross invoice
price received by the distributors will be used to determine End User Net
Commercial Sales. Notwithstanding the foregoing, End User Net Commercial Sales
shall not include products transferred for purposes of a clinical trial by
GEN-PROBE, the GEN-PROBE/CHIRON ALLIANCE, and the GEN-PROBE/BAYER ALLIANCE and
the use of such products for clinical trials will not be royalty bearing.

1.8 The term [***] shall refer to a recipient of license and rights
under the [***] granted hereunder as applicable.

*** Certain information on this page has been omitted and filed separately with
     the Commission. Confidential treatment has been requested with respect to
     the omitted portions.

                                  Page 2 of 12
<PAGE>
1.9 The term GEN-PROBE Core Licensee shall mean a third party to whom Gen-Probe
grants a royalty-bearing license in the field of infectious disease nucleic acid
testing under substantial patented core technology of Gen-Probe (a "Gen-Probe
Core Technology License"), including, by way of example and not of limitation,
Transcription Mediated Amplification.

                                    2. GRANTS

2.1 Subject to the terms and conditions of this Agreement, VYSIS hereby grants
to GEN- PROBE a worldwide, royalty-bearing, nonexclusive license without the
right to sublicense, to make, use, sell, offer for sale, or import Licensed
Products and practice Licensed Methods under the [***] for use in the
field of infectious disease nucleic acid testing.

2.2 The right to sell Licensed Products granted in Paragraph 2.1 shall extend to
distributors of GEN-PROBE relative to their distribution of Licensed Products
from GEN-PROBE with no additional obligation by the distributors to pay
royalties.

2.3 Except as otherwise provided herein, the licenses granted in paragraph 2.1
shall extend from June 22, 1999 until the date of expiration of the last to
expire of the [***].

2.4 Subject to the terms and conditions of this Agreement, VYSIS hereby agrees
to grant the following options to the following third parties:

      (a) For a period of six (6) months following June 22, 1999, VYSIS will
      grant to the GEN- PROBE/CHIRON ALLIANCE an option for a license under the
      [***]. The terms of the license will be the same terms granted
      to GEN-PROBE herein, except that such terms [***] as provided herein and
      the license will be granted solely for purposes of the blood screening
      aspects of the GEN-PROBE/CHIRON ALLIANCE.

      (b) For a period of six (6) months following June 22, 1999, VYSIS will
      grant to the GEN- PROBE/BAYER ALLIANCE an option for a license under the
      [***]. The terms of the license will be the same terms granted
      to GEN-PROBE herein, except that such terms [***] as provided herein and
      the license will be granted solely for purposes of infectious diseases
      aspects of the GEN-PROBE/BAYER ALLIANCE with the exception of blood
      screening.

      (c) For a period of twelve (12) months following June 22, 1999, VYSIS will
      grant to [***] and its subsidiaries an option for a license under the
      [***] at terms similar to the terms granted to GEN-PROBE herein (such
      terms shall include a license issue fee of [***] and running royalty
      similar to the royalty provided herein).

*** Certain information on this page has been omitted and filed separately with
     the Commission. Confidential treatment has been requested with respect to
     the omitted portions.

                                  Page 3 of 12
<PAGE>
      (d) For a period of six (6) months following the grant by GEN-PROBE of a
      Gen-Probe Core Technology License in a field of infectious disease nucleic
      acid testing to a GEN-PROBE Core Licensee, VYSIS will grant to the
      GEN-PROBE Core Licensee an option to a license under the [***] in the same
      field of infectious disease nucleic acid testing. The license under the
      [***] shall be at [***] (excluding the terms granted to GEN-PROBE, the
      GEN-PROBE/CHIRON ALLIANCE, the GEN- PROBE/BAYER ALLIANCE and [***]
      pursuant to this Agreement) and include a [***] herein relative to such
      other comparable [***].

2.5 For all purposes of this Agreement, each license granted pursuant to
paragraph 2.4 herein shall be regarded as a separate license under the [***] and
each corresponding licensee will be regarded as a separate licensee under the
[***].

                            3. ROYALTIES AND PAYMENTS

3.1 GEN-PROBE agrees for itself and on behalf of the GEN-PROBE/CHIRON ALLIANCE
and the GEN-PROBE/BAYER ALLIANCE receiving licenses as provided in Paragraph 2.1
to make the following payments for the licenses received hereunder:

      (a) A one-time license issue fee of [***] to be paid consistent with the
      payment provision of Paragraph 27 of the Definitive Agreement and Release
      executed concurrently with this Agreement by the parties hereto.

      (b) A running royalty of [***] of End User Net Commercial
      Sales of Licensed Products (the parties agree that a single royalty rate
      of [***] of End User Net Commercial Sales will apply as an
      aggregate rate in the event that one or more [***] apply to any
      End User Net Commercial Sales of Licensed Products);

3.2 Running royalties accruing to VYSIS hereunder shall be paid to VYSIS by each
[***] as applicable on a calendar quarterly basis for each quarter ending:

      (a)   March 31;
      (b)   June 30;
      (c)   September 30; and
      (d)   December 31

3.3 Royalty payments accruing hereunder shall be paid within sixty (60) days of
the close of each calendar quarter.

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                  Page 4 of 12
<PAGE>
3.4 All monies due VYSIS shall be payable in United States Dollars collectible
at par in Chicago, Illinois. When Licensed Products and Licensed Methods are
sold for monies other than United States Dollars, the earned royalties will
first be determined in the foreign currency of the country in which the Licensed
Products and Licensed Methods were sold and then converted into equivalent
United States Dollars. The applicable exchange rate will be that established by
the Bank of America in New York, New York on the last day of the reporting
period and will be quoted in the Continental terms method of quoting exchange
rates (local currency per U.S. dollar).

3.5 In the event that any [***] is required to withhold taxes imposed upon VYSIS
for any payment under this Agreement by virtue of the laws or governmental
regulations of a country in which Licensed Products are sold or Licensed Methods
are practiced, then such payments will be made by such [***] on behalf of VYSIS
by deducting from the payment due VYSIS and remitting such taxes to the proper
authorities on a timely basis and the payments provided for under this Agreement
will be adjusted appropriately provided that the [***] supplies VYSIS with
official documentation and/or tax receipt on such withholdings supporting such
taxes and such payments as may be required by VYSIS for its tax records. The
[***] shall be responsible for all bank transfer charges.

3.6 In the event royalty payments or fees due hereunder are not received by
VYSIS when due, the applicable [***] shall pay to VYSIS interest
charges at a rate of one percent (1%) per month. The interest shall be
calculated from the date the payment or fee was due to VYSIS until actually
received by VYSIS.

3.7 Royalties paid hereunder shall be accompanied by a report of the following:

      (a) Gross sales and End User Net Commercial Sales of Licensed Products and
      Licensed Methods by the reporting [***] in the preceding
      calendar quarter;

      (b) The number of each type of Licensed Product sold and Licensed Method
      performed;

      (c) The royalties, in U.S. dollars, payable hereunder as a result of such
      sales;

      (d) The method used to calculate the royalty; and

      (e) The exchange rate used to calculate the royalty in U.S. dollars.

All reports submitted hereunder shall be confidential. VYSIS will use the
reports only for the purpose of monitoring payment of royalties. Except as
required by law, VYSIS will not disclose any report or the information contained
in any report to any third party. If VYSIS believes that disclosure is warranted
by law or circumstances, it shall first give the appropriate [***]
notice and an opportunity to object. VYSIS shall take reasonable steps to
minimize the extent of any proper disclosure made after notice and opportunity
to object are provided to the appropriate [***].

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                  Page 5 of 12
<PAGE>
3.8 If, after a [***] has made its first commercial sale of License
Products or Licensed Method, no sale of Licensed Products or Licensed Method has
been made during any particular quarterly reporting period, the [***]
shall submit a report indicating that no sale was made in the period.

3.9 [***] shall keep books and records accurately showing all
Licensed Products manufactured, used and/or sold and Licensed Methods performed
commercially under the terms of this Agreement. Such books and records shall be
preserved for at least five (5) years from the date of the royalty payment to
which they pertain and shall be open to inspection by representatives or agents
of VYSIS at reasonable times and under reasonable conditions. All information
contained in the [***] books and records shall be confidential and
VYSIS will use the reports only for the purpose of monitoring payment of
royalties.

                             4. TERM AND TERMINATION

4.1 Unless otherwise terminated by operation of law or by acts of the parties in
accordance with the terms of this Agreement, this Agreement shall be in force
from June 22, 1999 and shall remain in effect for the life of the last-to-expire
of the [***].

4.2 Any termination of this Agreement shall not affect the following:

      (a) A [***] obligations that have accrued prior to
      termination ;

      (b) A [***] continuing obligation to indemnify VYSIS; and

      (c) VYSIS' or a [***] continuing obligation to maintain the
      confidentiality of the terms of this Agreement and any confidential
      information received from another party pursuant to this Agreement.

4.3 If a [***] should violate or fail to perform any material term or covenant
of this Agreement, VYSIS may give written notice of such default ("Notice of
Default") to the [***]. If the [***] should fail to take appropriate steps to
cure such default within sixty (60) days of the effective date of such Notice of
Default, VYSIS shall have the right to terminate the license and rights granted
to the [***] hereunder by issuing a second written notice (Notice of
Termination) to the [***]. Thereafter, the license and rights previously granted
to the [***] shall terminate automatically on the effective date of the Notice
of Termination. Such termination shall not relieve the terminated [***] of its
obligation to pay any royalty or license fees owing at the time of termination
and shall not impair any accrued right of VYSIS. Such termination shall not act
to terminate the license and right granted hereunder to any other [***],
provided that, VYSIS may exercise its rights under this Paragraph 4.3 separately
against any [***] who violates or fails to perform any material term or covenant
of this Agreement.

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                  Page 6 of 12
<PAGE>
4.4 GEN-PROBE or any other recipient of a license and rights pursuant to
Paragraphs 2.4(a) - (d) may each terminate their respective license and rights
(and any license which issues pursuant to those rights) upon written notice of
termination to VYSIS. Thereafter, the license and rights previously granted to
the applicable [***] shall terminate automatically on the effective
date of the Notice of Termination. Such termination shall have no effect on the
license and rights granted to any other [***] hereunder.

                               5. LIMITED WARRANTY

5.1 VYSIS represents and warrants that it is the owner of the [***]
and has the lawful right to grant the license and rights granted hereunder.

5.2 GEN-PROBE represents and warrants that it has the right and authority to
accept the rights and obligations provided herein for itself, the
GEN-PROBE/CHIRON ALLIANCE and the GEN- PROBE/BAYER ALLIANCE.

5.3 The license and rights provided herein are provided WITHOUT WARRANTY OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR ANY OTHER WARRANTY,
EXPRESS OR IMPLIED. VYSIS MAKES NO REPRESENTATION OR WARRANTY THAT THE LICENSED
PRODUCTS OR LICENSED METHODS WILL NOT INFRINGE ANY PATENT OR OTHER PROPRIETARY
RIGHT.

5.4 IN NO EVENT WILL VYSIS BE LIABLE FOR ANY INCIDENTAL, SPECIAL OR
CONSEQUENTIAL DAMAGES RESULTING FROM GEN-PROBE'S OR A [***] EXERCISE OF THIS
LICENSE OR ITS USE OF LICENSED PRODUCTS OR LICENSED METHODS.

                                6. PATENT MARKING

6.1 GEN-PROBE agrees that GEN-PROBE and each [***] will mark all Licensed
Products made, used or sold under the terms of this Agreement, or their
containers, with the patent number or numbers of any applicable [***] practiced
thereby.

                            7. NON-PARTY INFRINGEMENT

7.1 As used in this Article 7, the term Substantial Infringement shall mean
alleged non-licensed infringement by a non-party brought to VYSIS' attention by
a [***] wherein such non-licensed infringement accounts for [***] of the total
End User Net Commercial Sales for Licensed Product and Licensed Method in the
United States or Europe.

*** Certain information on this page has been omitted and filed separately with
    the Commission. Confidential treatment has been requested with respect to
    the omitted portions.

                                  Page 7 of 12
<PAGE>
7.2 In the event that a [***] hereunder believes that an unlicensed non-party to
this Agreement is substantially infringing any issued patent within the [***],
the [***] shall call this Substantial Infringement to VYSIS' attention in
writing and shall provide VYSIS with reasonable evidence of such non-licensed
infringing activity and the substantiality of the non-licensed infringing
activity by the non-party. However, the [***] will not notify the non-party
infringer without first obtaining the consent of VYSIS. VYSIS agrees that it
will use its best efforts to terminate such Substantial Infringement.

7.3 In the event the Substantial Infringement of the [***] continues and VYSIS
is unable to cause its termination, the [***] may request that VYSIS take legal
action against the Substantial Infringement of the [***] by the non-party. Any
such request by a [***] shall be in writing and shall include reasonable
evidence of such infringement and the damages such infringement is causing to
the [***]. If VYSIS is unable to cause the termination of such Substantial
Infringement within [***] of the effective date of the [***] request for same,
VYSIS shall, at its discretion, commence litigation against the non-party
infringer to cause the termination of the Substantial Infringement. [***]

7.4 If VYSIS fails to initiate litigation to terminate such Substantial
Infringement within [***] of the effective date of a [***] request for same, the
[***] obligation to pay royalties on End User Net Commercial Sales of Licensed
Product and Licensed Method in the affected country shall be suspended until
such time as VYSIS has commenced such litigation or such Substantial
Infringement has ceased.

7.4 VYSIS will maintain sole control of any such litigation for patent
infringement, bear all expenses for such litigation, and retain all recoveries
and damages awarded from such litigation as is initiated pursuant to Paragraph
7.3 above. However, the [***] requesting termination of the Substantial
Infringement will provide reasonable cooperation to VYSIS in VYSIS' litigation
against such non-party infringer.

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                  Page 8 of 12
<PAGE>
                                    8. [***]

                                     [***]

                               9. INDEMNIFICATION

9.1 Each [***] hereunder agrees to indemnify, hold harmless and defend VYSIS,
its officers, employees and agents against any and all claims, suits, losses,
damages, costs, fees, and expenses resulting from or arising out of the [***]
exercise of the license and rights granted herein including any sale,
manufacture or use of a Licensed Product or performance of a Licensed Method.
This indemnification will include, but not be limited to, any product liability.

9.2 VYSIS shall promptly notify the appropriate [***] in writing of any claim
which VYSIS believes it may have a right of indemnification under this
Agreement.

9.3 VYSIS will provide reasonable cooperation to each [***] that is indemnifying
and holding VYSIS harmless for a claim, suit, loss or damage pursuant to
Paragraph 9.1.

                                   10. NOTICES

10.1 Any notice or payment required to be given to either party shall be deemed
to have been properly given and to be effective (a) on the date of delivery if
delivered in person or (b) five (5) days after mailing by first-class certified
mail, postage paid, to the respective addresses identified below, or to such
other address as the applicable party shall designate by written notice to the
other party.

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                  Page 9 of 12
<PAGE>
If to VYSIS:

                                  VYSIS, INC.
                              3100 Woodcreek Drive
                             Downers Grove, IL 60515

                            Attention: Patent Counsel

If to GEN-PROBE:

                             GEN-PROBE INCORPORATED
                           10210 Genetic Center Drive
                               San Diego, CA 92121

                Attention: Vice President, Intellectual Property

If to the GEN-PROBE/CHIRON ALLIANCE:

                             GEN-PROBE INCORPORATED
                           10210 Genetic Center Drive
                               San Diego, CA 92121

                Attention: Vice President, Intellectual Property

                                       and

                               CHIRON CORPORATION
                               4560 Horton Street
                          Emeryville, California 94608

                           Attention: General Counsel

If to the GEN-PROBE/BAYER ALLIANCE:

                             GEN-PROBE INCORPORATED
                           10210 Genetic Center Drive
                               San Diego, CA 92121

                Attention: Vice President, Intellectual Property

                                       and

                                BAYER CORPORATION
                               5260 Horton Street
                            Emeryville, CA 94608-2916

                      Attention: VP, NAD Partner Management

                                  Page 10 of 12
<PAGE>
                                 11. ASSIGNMENT

11.1 This Agreement is binding upon and shall inure to the benefit of VYSIS, it
successors and assigns, but shall be personal to GEN-PROBE, the GEN-PROBE/CHIRON
ALLIANCE and the GEN-PROBE/BAYER ALLIANCE and personal relative to subsequent
GEN-PROBE Core Licensees. The applicable license and rights and options granted
herein to GEN-PROBE, the GEN-PROBE/CHIRON ALLIANCE, the GEN-PROBE/BAYER ALLIANCE
and to subsequent GEN-PROBE Core Licensees are not assignable by them except to:

      (a) A bona fide purchaser of all or substantially all of the business of
      the seller to which the license and rights pertain, provided that such
      bona fide purchaser agrees to the terms and conditions of this Agreement;
      and

      (b) A wholly-owned affiliate of GEN-PROBE, the GEN-PROBE/CHIRON ALLIANCE,
      the GEN-PROBE/BAYER ALLIANCE, or the GEN-PROBE Core Licensee as the case
      may be.

                                12. GOVERNING LAW

12.1 This Agreement is made in partial fulfillment of and reflects terms
specified in a Definitive Agreement and Release entered into by the parties in
settlement of litigation in the United States District Court for the Southern
District of California in the matter Gen-Probe, Incorporated v. Amoco Corp., et
al. (Case No. 95-CV-998-J(BTM)). The Agreement and its construction are subject
to the laws of the state of California with the exception of any choice of law
provisions which would direct the application of another state's laws. The
Agreement and its construction are further subject to the continuing
jurisdiction of the United States District Court for the Southern District of
California.

                               13. CONFIDENTIALITY

13.1 Except as required by law, the terms of this Agreement and all information
produced hereunder and designated as confidential by the producing party shall
be considered as confidential information of the producing party and the party
receiving such information shall use the same care to protect such information
as it uses to protect its own information of like kind.

                                14. MISCELLANEOUS

14.1 No amendment or modification hereof shall be valid or binding upon the
parties unless made in writing and signed by an authorized representative on
behalf of each party hereto.

                                  Page 11 of 12
<PAGE>
14.2 This Agreement embodies provisions of a Definitive Agreement and Release
entered into concurrently herewith by the parties in the matter Gen-Probe,
Incorporated v. Amoco Corp., et al. (Case No. 95-CV-998-J(BTM)) in the United
States District Court for the Southern District of California and such other
understandings as are included herein. This Agreement and the Definitive
Agreement and Release embody the entire understanding of the parties and shall
supercede all previous communications, representations or understandings either
oral or written, between the parties relating to the subject matter hereof.

14.3 In case any of the provisions contained in this Agreement shall be held
invalid, illegal or unenforceable in any respect, such invalidity, illegality or
unenforceability shall not affect any other provisions hereof and this Agreement
shall be construed as if such invalid or illegal or unenforceable provisions had
never been contained herein.

14.4 CHIRON, BAYER, [***], and GEN-PROBE Core Licensees are third party
beneficiaries of this Agreement as set forth above.

IN WITNESS WHEREOF VYSIS and GEN-PROBE have executed this Agreement, in
duplicate originals, by their respective officers hereunto duly authorized, on
the day and year written below.

VYSIS, INC.                                     GEN-PROBE INCORPORATED

By:    /s/                                      By:    /s/ Henry L. Nordhoff
       -----------------------                          -----------------------
Title: President & CEO                          Title: President & Chief Exec.
       -----------------------                         Officer
Date:  8/10/99                                         ------------------------
       -----------------------                  Date:  August 10, 1999
                                                       ------------------------

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                  Page 12 of 12
<PAGE>
                                                                       EXHIBIT 1

                               SCHEDULE OF [***]

                                     [***]

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                     1 of 2

<PAGE>

                                     [***]

*** Certain information on this page has been omitted and filed separately with
the Commission. Confidential treatment has been requested with respect to the
omitted portions.

                                     2 of 2

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