<PAGE>   1

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                                                   EXHIBIT 10.2

                                 TROPIX, INC.

                              RESELLER AGREEMENT

         THIS AGREEMENT is made as of the 22nd day of July, 1996, by TROPIX,
INC., a Delaware corporation ("Tropix"), with its principal place of business
at 47 Wiggins Avenue, Bedford, Massachusetts 01730, U.S.A., and Digene
Corporation, a Delaware corporation ("Digene"), with its principal place of
business at 2301-B Broadbirch Drive, Silver Spring, Maryland 20904, U.S.A..

                                   RECITALS

         The parties desire that the product of Tropix listed on Schedule A
hereto ("Product") shall be purchased by Digene and that Digene shall resell
the Product, all upon the terms and conditions set forth herein. The
definitions of capitalized terms used but not otherwise defined herein are set
forth in Schedule C hereto.

         The parties, in consideration of the mutual obligations hereinafter
set forth and intending to be legally bound, hereby agree as follows:

1.       APPOINTMENT AS RESELLER

         1.1 Tropix hereby appoints Digene as its nonexclusive reseller for
the sale, distribution and promotion of the Product, and Digene accepts such
appointment, subject to the restrictions set forth in this Section 1.

         1.2 Digene may only resell the Product (i) under Digene's label or a
joint Digene/Digene distributor label and (ii) only as a component of products
manufactured by Digene (and only Digene) which incorporate both the Product
and Digene's proprietary Hybrid Capture system for use in human in vitro
diagnostics or for pharmaceutical therapeutics research and development. In
the event that during the term of this Agreement, Digene develops one or more
products for the non-human diagnostic markets such as food and environmental
testing, and can demonstrate to Tropix reasonable satisfaction that
commencement of commercial sales is imminent, at Digene's request the parties
will negotiate in good faith a Reseller Agreement for the Product for use in
such Digene products for the non-human diagnostic markets. Tropix obligation
in such event shall be limited to negotiating such a Reseller Agreement in
good faith and nothing contained herein shall impose any obligation on Tropix
with respect thereto other than to so negotiate in good faith.

         1.3 Nothing contained in Section 1.2 shall be deemed to prohibit
International Murex Technologies Corporation ("Murex") from marketing and
selling products, manufactured b Digene, for the detection of infectious
diseases, which utilize Digene's proprietary Hybrid Capture system for use in
human in vitro diagnostics or for pharmaceutical therapeutics research and
development and which incorporate Product.

                                      1

<PAGE>   2

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

Murex shall have no other rights to the Product (including, without
limitation, the right to incorporate any Product into any Murex product) and
in all other respects the restrictions set forth in Section 1.2 and 1.5 shall
apply.

         1.4 In the event Digene proposes to resell Product under the label of
a third party but otherwise in accordance with Section 1.2 and 1.5, at
Digene's request Tropix will negotiate in good faith a Reseller Agreement with
such third party for the products to be sold under such third party's label.
Tropix obligation in such event shall be limited to negotiating such a
Reseller Agreement in good faith and nothing contained herein shall impose any
obligation on Tropix with respect thereto other than to so negotiate in good
faith.

         1.5 In no event shall Digene (a) dilute or alter the Product, (b)
resell the Product in the research or pharmaceutical screening markets or (c)
resell the Product for use in membrane-based assays.

         1.6 To the extent Tropix grants to any unrelated third party the
right to resell an improved formulation of the Product at any time during the
term of this Agreement, Tropix shall notify Digene of such improved
formulation of the Product. Upon notification, Digene shall have the option of
purchasing such improved formulation of the Product at a purchase price to be
agreed upon by the parties. Digene recognizes and agrees that any new,
improved or substitute dioxetane products and any new, improved or substitute
enhancer products manufactured, marketed and/or sold by Tropix will not
constitute an improved formulation of the Product and that this Agreement does
not provide Digene with any right to any new, improved or substitute
dioxetanes or enhancers.

2.       DIGENE'S OBLIGATIONS AND REPRESENTATIONS.  In addition to Digene's
obligations set forth elsewhere in this Agreement, Digene shall from and after
the date of this Agreement:

         2.1 Use reasonable commercial efforts to promote, develop a market
for and sell DNA probe assays, utilizing the Product, for human in vitro
diagnostics;

         2.2 Promptly respond to all customer complaints about the Product,
promptly notify Tropix of any recall or complaints; and

         2.3 Obtain, at its own expense, any import or export license, foreign
exchange license, foreign exchange permit, or other permit or approval it may
need for the resale of Product hereunder and otherwise comply with all laws,
regulations, rules and requirements governing the sale of the Product;
provided, however, that, at the request and expense of Digene, Tropix will aid
Digene in gaining regulatory approvals where help and information relating to
the Product is required.

         2.4 Digene represents to Tropix to the best of its knowledge that:

                                      2

<PAGE>   3

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                  (a) Digene is duly organized and validly existing in good
         standing under the laws of the State of Delaware, and has full
         corporate power and authority to enter into this Agreement and to
         carry out the provisions hereof;

                  (b) Digene has validly taken all requisite corporate action
         to properly authorize the execution of this Agreement and to fulfill
         its obligations hereunder;

                  (c) Digene has all the necessary corporate right, power and
         authority to enter into this Agreement; and

                  (d) Digene has carried on directly all negotiations with
         Tropix relative to this Agreement and is under no obligation or
         commitment to any person under which any brokerage commission or
         other compensation is payable with respect to the execution of this
         Agreement.

3.       PRICES AND TERMS OF SALE

         3.1 The prices for the Product are set forth in Schedule B. Such
prices are F.O.B. Tropix U.S. shipping facility, currently in Bedford,
Massachusetts. Tropix may adjust the price list once per year beginning
[****************] as provided in Schedule B. Tropix will notify Digene not
later than thirty (30) days prior to the effective date of any such price
increase.

         No later than December 1 of each year, Digene shall deliver to Tropix
a non-binding forecast of the quantity of Product it estimates it will
purchase under this Agreement during the forthcoming calendar year, and the
prices for the Product for such year shall be based upon the assumption that
Digene in fact will purchase the forecasted quantity during such year. If
Digene in fact purchases less than the quantity of Product it forecasted it
would purchase during such year, within thirty (30) days after the conclusion
of such year, Digene shall pay to Tropix the difference, if any, between the
aggregate purchase price paid by Digene for Product purchased during such year
and the aggregate purchase price Digene should have paid for the Product
purchased during such year based upon the quantities actually purchased, and
if Digene in fact purchases more than the quantity of Product it forecasted it
would purchase during such year, within thirty (30) days after the conclusion
of such year, Tropix shall pay to Digene the difference between the aggregate
purchase price paid by Digene for Product purchased during such year and the
aggregate purchase price Digene should have paid for the Product purchased
during such year based upon the quantities actually purchased.

         If this Agreement shall expire or terminate other than at a calendar
year end, for purposes of determining any amounts payable pursuant to the
preceding paragraph, the quantities of Product purchased during such year
prior to the date of expiration or termination shall be annualized, and within
thirty (30) days after the date of such expiration or termination, Digene
shall make

                                      3

<PAGE>   4

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

the payment to Tropix or Tropix shall make the payment to Digene, as the case
may be, contemplated by the preceding paragraph based upon such annualization.

         3.2 All shipments will be invoiced at the time of shipment, including
partial shipments. Digene assumes and agrees to pay and hold Tropix harmless
from all export or import duties, fees or other charges, all sales, use,
excise, value added or other taxes or assessments applicable to any sale under
this Agreement (but excluding taxes, together with any interest or penalties
imposed in connection therewith, on Tropix's gross revenues or profits), and
all costs and charges for transportation, brokerage, handling and insurance of
the Product from the point of shipment.

         3.3 Except for the technology access fee pursuant to Section 3.4 and
the royalties pursuant to Section 3.5, all payments required hereunder are due
within thirty (30) days of invoicing. All payments shall be in U.S. Dollars at
Tropix's principal place of business, without deduction or offset (except as
expressly authorized herein or in writing in advance by Tropix). If Tropix at
any time has reasonable concern about security or timeliness of payments, it
may decline to make shipments until receipt of payment or establishment of a
letter of credit or other arrangement securing payment. Tropix may impose
interest on overdue payments at the lesser of (i) 1-1/2% per month or (ii) the
maximum legal rate of interest.

         3.4 In addition to the price listed on Schedule B, Digene shall pay
Tropix a technology access fee in the amount of $[*******], payable as of the
date of this Agreement, such technology access fee will be credited against
the first $[*******] of royalties due to Tropix as set forth in Section 3.5.

         3.5 In addition to the price listed on Schedule B, Digene shall,
subject to Section 3.4, pay Tropix royalties as set forth in Schedule B,
payable with each report submitted pursuant to Section 3.7.

         3.6 Digene shall keep complete and accurate books of account
containing all particulars that may be necessary for the purpose of showing
the amounts payable to Tropix hereunder. Said books of account shall be kept
at Digene's principal place of business or the principal place of business of
the appropriate division of Digene to which this Agreement relates. Said books
and the supporting data shall be open for five (5) years following the end of
the calendar year to which they pertain, to the inspection of Tropix or its
agents for the purpose of verifying Digene's royalty statements or compliance
in other respects with this Agreement during Digene's ordinary business hours,
not more than once in any 12-month period. Should such inspection lead to the
discovery of more than a 10% discrepancy, Digene shall pay the full cost of
such inspection.

         3.7 Within forty-five (45) days after each March 31, June 30,
September 30 and December 31, Digene shall deliver to Tropix reports stating
(a) the number of Tests sold (or otherwise disposed of in a transaction which
generated Net Sales) by Digene; (b)

                                      4

<PAGE>   5

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

Net Sales of Tests; (c) applicable deductions; (d) total royalties due and
payable, and (e) such other information regarding Digene's business under this
Agreement as Tropix shall reasonably request. If no royalties shall be due,
Digene shall so report. "Tests" and "Net Sales" shall have the meanings set
forth on Schedule C.

         3.8 Minimum Purchases are set forth in Schedule A. If Digene fails to
make Minimum Purchases for any applicable period set forth in Schedule A,
Tropix may terminate this Agreement as set forth in Section 5.2 without
incurring any obligation of any kind to Digene, provided, however, that Tropix
shall first notify Digene of its intent to terminate the agreement and Digene
shall then have 45 days to acquire the minimum purchase amount.

4.       ORDERS AND SHIP

         4.1 Digene shall submit orders at least forty-five (45) days prior to
the requested delivery dates on a purchase order referencing this Agreement.
Digene shall purchase at least the Minimum Purchase amounts not later than the
times set forth in Schedule A hereto.

         4.2 Tropix may specify a different ship date by written notice within
seven (7) days after receipt of an order but otherwise will use commercially
reasonable efforts to ship orders by the requested date. Shipments shall be in
accordance with Digene's instructions, but unless other written instructions
are provided by Digene, Tropix will select the common carrier and shall prepay
freight, insurance, and other reasonable and customary or necessary charges
and invoice them to Digene. All Product will be properly packed.

         4.3 The terms and provisions herein and no others shall govern all
orders and purchases notwithstanding any inconsistent or additional terms on
purchase orders or forms, which inconsistent or additional terms shall have no
force or effect whatsoever as between the parties even if Tropix might be
deemed to have accepted same by reason of its execution or acknowledgment
thereof.

         4.4 In the event Tropix is unable to supply Product to Digene and
such failure to supply continues for a period of six consecutive (6) months,
thereafter Tropix will grant Digene a non-exclusive license under Tropix
appropriate patents and know-how to enable Digene to manufacture such Product
solely to the extent necessary to enable Digene to substitute itself for
Tropix as a source of supply for the Product Tropix is unable to supply to
Digene. The terms and conditions of any license agreement granted pursuant to
this Section shall be the subject of good faith negotiations between Tropix
and Digene and shall include the payment of royalties to Tropix. In any event,
any rights granted to Digene under this Section (i) shall continue until the
earlier to occur of the expiration of this Agreement or such date as Tropix
advises Digene that it is able to supply such Product to Digene and (ii) are
limited to Digene only, and in no

                                      5

<PAGE>   6

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

event may Digene assign, delegate or otherwise transfer any of its rights
under this Section to any other party, including without limitation, its
subsidiaries or distributors.

5.       TERM AND TERMINATION

         5.1 This Agreement shall commence on the date first set forth above
and shall extend for a period of ten (10) years, subject to earlier
termination as provided herein. The parties may renew this Agreement after the
initial term upon express mutual agreement in writing at least ninety (90)
days prior to the expiration of the initial term, but if they do not, this
Agreement shall automatically expire at the end of the initial term, provided,
however, that Tropix shall have notified Digene at least six months in advance
of the expiration date of its intent not to renew the Agreement.

         5.2 This Agreement shall not, however, be terminated as to any Digene
products (and only such Digene products) which incorporate both the Product
and Digene's proprietary Hybrid Capture system for use in human in vitro
diagnostics as to which Digene has commenced FDA approval trials so long as
(i) Digene diligently prosecutes its application for FDA approval of such
product and (ii) if FDA approval is obtained, Digene is using commercially
reasonable efforts to market the approved products.

         5.3 Notwithstanding anything herein contained to the contrary, and in
addition and without prejudice to any other rights or remedies, the parties
shall have the right to terminate this Agreement as follows:

                  (a) either party may terminate this Agreement effective
         immediately upon written notice if (i) the other party fails to make
         any payment due hereunder within ten (10) days after the date such
         payment was due and the payment has not been made within 20 days
         after such notice or (ii) the other party is in material breach of
         the terms hereof, provided, however, that if the material breach is
         capable of remedy, termination shall be effective thirty (30) days
         after notice specifying the breach and such remedy if the breach
         shall not have been remedied within such period;

                  (b) either party may terminate this Agreement effective
         immediately upon written notice if (i) all or a substantial portion
         of the assets of the other party are transferred to an assignee for
         the benefit of creditors, a receiver, or a trustee in bankruptcy,
         (ii) a proceeding is commenced by or against the other party for
         relief under bankruptcy or similar laws and such proceeding is not
         dismissed within thirty (30) days, (iii) the other party is adjudged
         insolvent or bankrupt; or (iv) if the other party shall cease to
         carry on business;

                  (c) Tropix may terminate this Agreement effective
         immediately upon written notice if Digene is in breach of Section
         1.2, 7, 8 or 9 of this Agreement, provided, however, that Tropix
         shall first notify Digene of its intent to terminate

                                      6

<PAGE>   7

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

         the Agreement and Digene shall then have forty-five (45) days to
         remedy such breach;

                  (d) Tropix may terminate this Agreement effective
         immediately upon written notice if Digene shall fail to make the
         Minimum Purchases set forth on Schedule A for any applicable period
         set forth in said Schedule; provided however that Tropix shall first
         notify Digene of its intent to terminate the Agreement and Digene
         shall then have forty-five (45) days to acquire the Minimum Purchase
         amount;

                  (e) Tropix may terminate this Agreement effective upon
         thirty (30) days prior written notice if, during the first three
         years of the term hereof, Digene shall not have filed and be
         diligently prosecuting, applications with the United States Food and
         Drug Administration ("FDA") for commercial sales of at least four
         Digene Hybrid Capture Infectious Disease tests each of which
         incorporates Product for use in human in vitro diagnostics, provided,
         however, that this Agreement shall not be terminated as to any Digene
         products (and only such Digene products) which incorporate both the
         Product and Digene's proprietary Hybrid Capture system for use in
         human in vitro diagnostics as to which Digene has commenced FDA
         approval trials so long as (i) Digene diligently prosecutes its
         application for FDA approval of such product and (ii) if FDA approval
         is obtained, Digene is using commercially reasonable efforts to
         market the approved products;

                  (f) Tropix may terminate this Agreement upon ninety (90)
         days prior written notice in the event that for any [********] period
         Digene shall neither have developed nor, through the application of
         substantial resources, be actively and continuously engaged in the
         development of additional products incorporating the Product;
         provided, however, that this Agreement shall not be terminated as to
         any Digene products (and only such Digene products) which incorporate
         both the Product and Digene's proprietary Hybrid Capture system for
         use in human in vitro diagnostics as to which Digene has commenced
         FDA approval trials so long as (i) Digene diligently prosecutes its
         application for FDA approval of such product and (ii) if FDA approval
         is obtained, Digene is using commercially reasonable efforts to
         market the approved products; and

                  (g) Tropix may terminate this Agreement upon ninety (90)
         days prior written notice in the event Digene's Net Sales fall below
         [*************] dollars per calendar year for any year beginning with
         the [*********], provided however that Tropix shall first notify
         Digene of its intent to terminate the Agreement and Digene shall then
         have forty-five (45) days to pay to Tropix the royalties which would
         have been due under Section 3.5 based upon Net Sales of
         [*************] dollars; and further provided, that this Agreement
         shall not be terminated as to any Digene products (and only such
         Digene products) which incorporate both the

                                      7

<PAGE>   8

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

         Product and Digene's proprietary Hybrid Capture system for use in
         human in vitro diagnostics as to which Digene has commenced FDA
         approval trials so long, as (i) Digene diligently prosecutes its
         application for FDA approval of such product and (ii) if FDA approval
         is obtained, Digene is using commercially reasonable efforts to
         market the approved products.

         5.4 Digene acknowledges that this Agreement shall, unless the parties
mutually agree otherwise, continue only until the expiration of the term. With
such knowledge in mind, Digene has agreed to the pricing structure provided
for in this Agreement as full, fair and sufficient compensation for all
efforts and services to be performed by Digene. Accordingly, in the event of
termination or expiration in accordance with this Agreement neither party
shall be entitled to any indemnity, compensation, damages, loss of profits or
prospective profits, or payment in respect of investments made or goodwill or
clientele established during the continuance of this Agreement. Digene hereby
waives all rights to compensation and damages in connection therewith to which
it may otherwise be entitled under the law of any jurisdiction.

         5.5 The obligations of Digene under Sections 1.2, 1.5, 3.4, 3.5, 3.6,
3.7.6.6, 7, 8, 9 or 11 shall not be affected by termination or expiration. The
obligations of Tropix under Sections 6, 9 or 11 shall not be affected by
termination or expiration.

6.       LIMITED REPRESENTATIONS AND PRODUCT WARRANTIES

         6.1 Tropix sole warranties are that each Product supplied to Digene
will, for the period specified in the Product Specifications, conform to the
Product Specifications. Tropix will provide a Certificate of Analysis with
each shipment. Tropix makes the foregoing warranties to and for the benefit of
Digene only, and they may not be assigned to any other party.

         6.2 If any Product does not conform with the foregoing warranties,
Tropix sole obligation with respect thereto shall be to replace such Product
without charge or expense to Digene or, at Tropix option, to credit Digene for
the amount paid by Digene to Tropix for such Product.

         6.3 The above warranties are contingent upon the proper use, storage
and shipment of the Product and shall be void with respect to defects or
failures due to disaster, accident, neglect, misuse, or improper storage or
shipment (in each case not attributable to Tropix).

         6.4 Tropix represents to Digene to the best of its knowledge that:

                  (a) Tropix is duly organized and validly existing in good
         standing under the laws of the State of Delaware, and has full
         corporate power and authority to enter into this Agreement and to
         carry out the provisions hereof;

                                      8

<PAGE>   9

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                  (b) Tropix has validly taken all requisite corporate action
         to properly authorize the execution of this Agreement and to fulfill
         its obligations hereunder;

                  (c) Tropix has all the necessary corporate right, power and
         authority to enter into this Agreement and to grant to Digene the
         rights hereunder; and

                  (d) Tropix has carried on directly all negotiations with
         Digene relative to this Agreement and is under no obligation or
         commitment to any person under which any brokerage commission or
         other compensation is payable with respect to the execution of this
         Agreement.

         6.5 EXCEPT AS EXPRESSLY SET FORTH IN SECTION 6.1, THERE ARE NO
WARRANTIES, EXPRESS OR IMPLIED, BY OPERATION OF LAW OR OTHERWISE, WITH RESPECT
TO THE PRODUCTS, AND TROPIX EXPRESSLY DISCLAIMS ALL IMPLIED WARRANTIES AND
WARRANTIES ARISING BY OPERATION OF LAW INCLUDING BUT NOT LIMITED TO ANY
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. NO
REPRESENTATION OR OTHER AFFIRMATION OF FACT, INCLUDING BUT NOT LIMITED TO
STATEMENTS REGARDING CAPACITY, SUITABILITY FOR USE OR PERFORMANCE OF PRODUCTS,
WHETHER MADE BY TROPIX EMPLOYEES OR OTHERWISE, WHICH IS NOT CONTAINED IN THIS
AGREEMENT SHALL BE DEEMED TO BE A WARRANTY BY TROPIX FOR ANY PURPOSE OR GIVE
RISE TO ANY LIABILITY OF TROPIX WHATSOEVER. WITHOUT LIMITATION OF THE
FOREGOING, TROPIX IS NOT EXTENDING ANY REPRESENTATION OR WARRANTY THAT THE
PRODUCTS, ALONE OR IN COMBINATION WITH OTHER PRODUCTS, WILL NOT INFRINGE THE
PATENTS OR OTHER RIGHTS OF THIRD PARTIES. IN NO EVENT SHALL TROPIX BE LIABLE
FOR INDIRECT, INCIDENTAL, CONSEQUENTIAL OR SPECIAL DAMAGES, INCLUDING WITHOUT
LIMITATION LOST BUSINESS PROFITS, REGARDLESS WHETHER THE ACTION IS IN
CONTRACT, TORT (INCLUDING NEGLIGENCE), BREACH OF WARRANTY OR OTHERWISE, EVEN
IF TROPIX HAS BEEN ADVISED AS TO THE POSSIBILITY THEREOF.

         6.6 If Digene makes any warranty or representation inconsistent with
or in addition to the foregoing warranties, Digene shall defend and hold
Tropix harmless from any claim to the extent based thereon.

         6.7 Tropix shall maintain policies of comprehensive general liability
insurance, including product liability insurance, with limits of at least
[*******************************************].

7.       TRADEMARKS AND TRADE NAMES

         7.1 Subject to Section 7.2, Tropix grants to Digene a non-exclusive
right to use the trademarks, marks, trade names and logos that Tropix may
adopt from time to time with respect to the Product ("Tropix Marks") in
connection with Digene's sale and

                                      9

<PAGE>   10

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

distribution of Product. Digene will indicate clearly in any and all materials
in which Tests utilizing the Product are advertised, marketed, sold or
otherwise distributed that such Tests utilize Product obtained by Digene from
Tropix. Except as set forth in this Section 7, nothing contained in this
Agreement will grant to Digene any right, title or interest in Tropix Marks.
Digene recognizes the validity of Tropix Marks and acknowledges the same are
the property of Tropix. At no time during or after the term of this Agreement
will Digene challenge or assist others to challenge Tropix Marks or the
registration thereof or attempt or assist others to attempt to register any
trademarks, marks, trade names or logos confusingly similar to those of
Tropix.

         7.2 All representations of Tropix Marks that Digene intends to use
will first be submitted to Tropix for approval (which will not be unreasonably
withheld) of design, color, and other details or will be exact copies of those
used by Tropix. In addition, Digene shall follow the instructions issued by
Tropix from time to time for the purpose of protecting the standards of
quality established for the goods and services sold under Tropix Marks.

8.       PATENT MARKING

         Digene shall properly affix the statutory patent notice to all
Product or, where that is impractical, to labels or boxes for such Product.

9.       CONFIDENTIAL INFORMATION.

         Each party shall treat accordingly all verbal and written
communications from the other party which are designated, or which should
reasonably be regarded, in the normal commercial view, as constituting
business secrets or proprietary information ("Proprietary Information"). Each
party shall refrain from using, disclosing or making available to any third
party any of the other party's Proprietary Information without the other
party's written consent and shall impose upon its employees and agents the
same obligations with respect to the other party's Proprietary Information as
it employs with respect to its own confidential information but in no event
shall such obligations be less than what is appropriate in accordance with
good commercial practice. No such obligations of confidence shall extend to
information which (a) is publicly available; (b) is already in the receiving
party's possession; (c) is rightfully received from a third party; or (d) is
required by law to be disclosed, but solely to the extent of such requirement,
and in such event, the party required to disclose shall identify information
so disclosed as the confidential information of the other party, shall give
written notice of such requirement to the other party as long as possible
prior to such disclosure, and shall use all reasonable efforts to cause, or to
assist the other party to cause, such government, agency or organization to
protect such information as confidential.

10.      NOTICES.

                                      10

<PAGE>   11

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

         Any notice under this Agreement shall be effective when delivered to
the address of such party set out above (or to such other address as either
party may specify by notice given to the other party), addressed in the case
of Tropix to:

         Irena Bronstein
         President & CEO
         Tropix, Inc.
         47 Wiggins Avenue
         Bedford, MA 01730

         with a copy to its General Counsel, and in the case of Digene to:

<TABLE>
<S>                                             <C>
                                                 General Counsel
         Evan Jones                              Morris Cheston, Jr.
         President & CEO                         Ballard Spahr Andrews & Ingersoll, LLP
         Digene Corporation                      1735 Market Street
         9000 Virginia Manor Rd. Suite 206       51st Floor
         Beltsville, MD 20705                    Philadelphia, PA  19103-7599
</TABLE>


11.      DISPUTE RESOLUTION.

         Any dispute relating to the interpretation, performance, or damages
resulting from improper termination, of this Agreement shall be resolved, at
either party's written request, through final, binding arbitration; provided,
however, that nothing contained herein shall be construed to prevent either
party from terminating this Agreement or from bringing an action in any court
of competent jurisdiction to compel the other party to comply with orders or
awards of the arbitrator(s) in the nature of injunctive or provisional relief
during the pendency of the arbitration proceedings. Such arbitration shall be
conducted in Boston, Massachusetts, in accordance with the Commercial
Arbitration Rules and (if applicable) Supplementary Procedures for
International Commercial Arbitration, both as modified from time to time, of
the American Arbitration Association ("AAA"). The arbitrator (or at least one
of the arbitrators if there are three) shall be an experienced business
attorney skilled in the subject matter of the dispute. The arbitrator(s) shall
assess the fees and expenses of the AAA and the arbitrator(s) between the
parties in such proportions as the arbitrator(s) deem equitable. Punitive
damages (including multiple damages) may not be awarded in any arbitration
hereunder. If judicial enforcement or review of the arbitrator(s)' award is
sought by either party, judgment may be entered upon such award in any court
of competent jurisdiction.

12.      MISCELLANEOUS

                                      11

<PAGE>   12

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

         12.1 All obligations of Tropix under this Agreement shall be subject
to the U.S. export laws, and Tropix shall not be liable for any failure to
perform hereunder if such performance is at that time prohibited by the U.S.
export laws.

         12.2 If Digene learns of any infringement of Tropix's patents, Tropix
Marks or other intellectual property rights, Digene shall promptly inform
Tropix in writing of all known information relating thereto and shall
cooperate fully with Tropix, at Tropix' expense, in any reasonable efforts
undertaken by Tropix to challenge or prosecute such infringement.

         12.3 This Agreement may not be assigned or transferred by Digene or
Tropix without the prior written consent of the other party; provided,
however, that the foregoing shall not be deemed to prohibit any assignment of
this Agreement by Tropix in connection with a sale or other transfer of all or
a substantial portion of its business relating to any Product or to a
corporation or other entity into which Tropix is merged or consolidated.

         12.4 No modification or waiver of any terms or conditions hereof
shall be of any force or effect unless in writing and signed by each party's
authorized officer. Either party's failure to enforce any provision shall not
be deemed to be a waiver of such provision or such party's right thereafter to
enforce such provision.

         12.5 Digene shall act as an independent contractor and shall not be
deemed to be an employee, agent, or legal representative of Tropix for any
purpose hereunder. Digene shall not be entitled to enter into any contracts in
the name of or on behalf of Tropix, nor to pledge the credit of Tropix in any
way or hold itself out as having authority to do so.

         12.6 This Agreement, along with the attachments referenced herein,
embodies the final, complete and exclusive understanding between the parties,
and supersedes all previous agreements, understandings and arrangements
between the parties with respect to the subject matter contained herein.

         12.7 If any provision of this Agreement is held illegal, invalid or
unenforceable, all other provisions hereof shall remain in full force and
effect as if such provision were not a part hereof.

         12.8 Except as otherwise specifically provided herein, this Agreement
shall be governed by and construed according to the laws of Massachusetts,
U.S.A., excluding both its choice of law provisions and the United Nations
Convention on Contracts for the International Sale of Goods.

         12.9 Except as otherwise provided herein, if the performance of this
Agreement or any obligation hereunder (other than the making of payments
hereunder) is prevented, restricted or interfered with by reason of any event,
act or condition beyond

                                      12

<PAGE>   13

THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

the reasonable control of the affected party, the party so affected, upon
written notice to the other party, shall be excused from such performance to
the extent of such prevention, restriction or interference

         12.10 The headings and captions in this Agreement are for convenience
only and are not part of this Agreement.

         12.11 The following attachments are incorporated in and made a part
of this Agreement:

                  (i)      Schedule A: Product and Minimum Purchases

                  (ii)     Schedule B: Price List

                  (iii)    Schedule C: Definitions

                  (iv)     Schedule D: Product Specification

                                      13

<PAGE>   14


THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

IN WITNESS WHEREOF, the undersigned have executed and delivered this Agreement
by their duly authorized representatives as of the date first shown above.



<TABLE>
<CAPTION>
   TROPIX, INC.                              DIGENE CORPORATION
   <S>                                      <C>
   By: /s/Nancy E. Watters                   By: /s/Evan Jones
      -------------------------------           -----------------------------
   Name: Nancy E. Watters                    Name: Evan Jones
        -----------------------------             ---------------------------
   Title: General Counsel                    Title: President & CEO
         ----------------------------              --------------------------
   Date: July 22, 1996                       Date: August 1, 1996
        -----------------------------             ---------------------------
</TABLE>

                                      14

<PAGE>   15



THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                  SCHEDULE-A

                        PRODUCT AND MINIMUM PURCHASES


<TABLE>
<S>                  <C>
Product:              [*****] CDP-Star(R) with [************] of
                      Emerald-II(TM) Enhancer in [*************].

Minimum               [***] Liters of Product in [****].
Purchases:
                      [***] Liters of Product in [****].

                      [***] Liters of Product in [****].

                      [***] Liters of Product in [****].
</TABLE>


<PAGE>   16


THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                  SCHEDULE B

                             PRICES AND ROYALTIES

Price per liter of Product based upon aggregate purchases per calendar year*:

                [**] liters                    $  [***]/liter
                [******] liters                $  [***]/liter
                [*****] liters                 $  [***]/liter



*In [**************], price per liter of Product will be $ [***]/liter.

Beginning [*****************], each of the foregoing prices may be changed by
multiplying such price by a fraction, the numerator of which shall be the
Index as of the most recent date available prior to the date of such change
and the denominator of which shall be the Index as of the most recent date
available prior to the date of the Agreement to which this Schedule B is
attached. As used herein, "Index" shall mean the Producer Price Index
published by the U.S. Department of Labor.

Royalty Rate:

The first $[*********] of Net                [***]% of Net Sales of Tests,
Sales, the greater of:                       or $[****] per Test.

                                             [***]% of Net Sales of Tests,
Thereafter, the greater of:                  or $[****] per Test.

<PAGE>   17


THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                  SCHEDULE C

                                  DEFINITION

1        "Net Sales" shall mean the aggregate gross invoiced sales price of
all Tests (as hereinafter defined) sold by Digene, less:

         (a)      any promotional samples, rebates or discounts offered as
                  sales incentives (in amounts not to exceed amounts that are
                  normal and customary in substantially similar
                  circumstances);

         (b)      any taxes or other governmental charges levied directly on
                  sales that are borne by the seller;

         (c)      any transportation or delivery costs that are borne by the
                  seller and separately stated on the invoice; and

         (d)      refunds or credits for defective or returned Tests.

No deductions shall be made for cash discounts, commissions, cost of
collections, or uncollectible accounts. Tests shall be considered "sold" when
billed out or invoiced. Where Tests are not sold but are otherwise disposed
of, Net Sales with respect to such Tests otherwise disposed of shall be the
selling price at which Tests sold in similar quantities are then being offered
for sale by Digene. Sales of Tests by Digene to an entity controlling,
controlled by or under common control with Digene shall be excluded from Net
Sales provided that such entity is purchasing for resale and any such resales,
when made, are included in determining Net Sales.

2.       "Test" shall mean a single DNA probe assay utilizing Product,
regardless of use for duplicates, standards or controls, manufactured and/or
sold by Digene.



<PAGE>   18


THIS EXHIBIT HAS BEEN REDACTED AND IS THE SUBJECT OF A CONFIDENTIAL TREATMENT
REQUEST. REDACTED MATERIAL IS MARKED WITH "*" AND BRACKETS AND HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                  SCHEDULE D

                            PRODUCT SPECIFICATIONS

<TABLE>
<S>                                  <C>
    Product:                          [******] CDP-Star(R) with [************] of
                                      Emerald-II(TM) enhancer in [****************].

    [**************]:                 [*********************************************
                                      **********************************************
                                      *******************************]

                                      [*********************************************
                                      **********************************************
                                      **********************************************
                                      *******************************].

                                      [*********************************************
                                      ********************]

    Storage Conditions:               4 degrees C

    Stability/Shelf Life:             one (1) year at 4 degrees C

    Packaging:                        High density polyethylene (HDPE) amber Nalgene bottles.

    Shipping Conditions:              Room temperature.
</TABLE>