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                                                                   EXHIBIT 10.42

                   HESKA CORPORATION STOCK PURCHASE AGREEMENT


         This STOCK PURCHASE AGREEMENT (this "Agreement"), is made and entered
into as of February 1, 2001, by and among HESKA CORPORATION, a Delaware
corporation (the "Company"), and the purchasers listed on Schedule A attached
hereto (collectively, the "Purchasers" and individually, a "Purchaser").

         1. Authorization of Sale of the Shares. Subject to the terms and
conditions of this Agreement, the Company has authorized the sale of up to
6,800,000 shares (the "Shares") of common stock, par value $0.001 per share (the
"Common Stock"), of the Company.

         2. Agreement to Sell and Purchase the Shares.

                  2.1 Purchase and Sale. Subject to the terms and conditions of
this Agreement, each Purchaser severally agrees to purchase, and the Company
agrees to sell and issue to each Purchaser, at the Closing (as defined below)
that number of Shares set forth opposite such Purchaser's name on Schedule A
attached hereto.

                  2.2 Purchase Price. The purchase price of each Share (the "Per
Share Price") shall be $1.247. The Company will not, for ninety (90) days after
the Closing Date (as defined below) without adjusting the Per Share Price
hereunder accordingly, sell (i) Shares at a price per share of less than $1.247,
or (ii) options, warrants or any other securities that can be converted into, or
otherwise exchanged for, shares of the Company's common stock at a conversion or
exercise price per share less than $1.247, other than to employees, directors
and consultants under existing stock plans or issued warrants. In the event the
Company shall, during the period beginning on the date of this Agreement and
ending ninety (90) days after the Closing Date, sell any shares of the Company's
common stock or any instruments that can be converted into or otherwise
exchanged for the Company's common stock (the "Subsequent Sale") exercisable at
a price per share (the "Subsequent Purchase Price") of less than $1.247 per
share, the purchase price per Share hereunder shall be adjusted to an amount
equal to the Subsequent Purchase Price, such that the Company shall, within ten
(10) business days of the Subsequent Sale, pay to the Purchaser, at the
Purchaser's option in either cash or additional shares of the Company's Common
Stock, an amount equal to the number of Shares times the difference between
$1.247 and the Subsequent Purchase Price. If the Purchaser elects to receive
Common Stock, the Common Stock shall be valued at the price at which the Company
sells any such shares (or securities that may converted into or exchanges for
shares) of Common Stock.

         3. Delivery of the Shares at the Closing.

                           (a) The completion of the purchase and sale of the
Shares (the "Closing") shall occur at the offices of Wilson Sonsini Goodrich &
Rosati, PC counsel to the Company, at One

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Market Plaza, Spear Street Tower, Suite 3300, San Francisco, California 94105 at
9:00 a.m. local time on February 6, 2001 or such other time and date as may be
agreed by the parties (the "Closing Date").

                           (b) At the Closing, the Company shall authorize its
transfer agent (the "Transfer Agent") to issue to each Purchaser one or more
stock certificates registered in the name of such Purchaser, or in such nominee
name(s) as designated by such Purchaser in writing, representing the number of
Shares set forth in Section 2 above and bearing an appropriate legend referring
to the fact that the Shares were sold in reliance upon the exemption from
registration provided by Section 4(2) of the Securities Act of 1933, as amended
(the "Securities Act"), and Rule 506 under the Securities Act. The Company will
deliver certificates in such denominations as requested by the Purchasers (the
"Certificates") against delivery of payment for the Shares by the Purchasers.
Prior to the Purchasers' delivery of payment for the Shares, the Company will
deliver via facsimile a copy of the Certificates to be delivered upon Closing to
the office of the Purchasers (at the fax number indicated on the signature pages
attached hereto).

                           (c) The Company's obligation to complete the purchase
and sale of the Shares shall be subject to the following conditions, any one or
more of which may be waived by the Company:

                                    (i) receipt by the Company of same-day funds
in the full amount of the purchase price for the Shares being purchased under
this Agreement; and

                                    (ii) the accuracy in all material respects
of the representations and warranties made by the Purchasers and the fulfillment
in all material respects of those undertakings of the Purchasers to be fulfilled
before the Closing.

                           (d) The Purchasers' obligations to accept delivery of
such stock certificates and to pay for the Shares evidenced by the certificates
shall be subject to the following conditions, any one or more of which may be
waived by a Purchaser with respect to such Purchaser's obligation:

                                    (i) the representations and warranties made
by the Company in this Agreement shall be accurate in all material respects and
the undertakings of the Company shall have been fulfilled in all material
respects on or before the Closing;

                                    (ii) the Company shall have delivered to the
Purchasers a certificate executed by the chairman of the board or president and
the chief financial or accounting officer of the Company, dated the Closing
Date, in form and substance reasonably satisfactory to the Purchasers, to the
effect that the representations and warranties of the Company set forth in
Section 4 hereof are true and correct in all material respects as of the date of
this Agreement and as of the Closing Date, and that the Company has complied
with all the agreements and satisfied all the conditions in this Agreement on
its part to be performed or satisfied on or before the Closing Date; and


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                                    (iii) the Company shall have delivered to
Purchasers a legal opinion in substantially the form attached hereto as Exhibit
A.

                                    (iv) the Company shall have obtained gross
proceeds of at least $4,000,000.00 from the sale of the Shares at the Closing.

         4. Representations, Warranties and Covenants of the Company. Except as
set forth on the Schedule of Exceptions attached hereto as Exhibit B, the
Company hereby represents and warrants to the Purchasers as follows (which
representations and warranties shall be deemed to apply, where appropriate, to
each subsidiary of the Company):

                  4.1 Organization and Qualification. The Company has been duly
incorporated and is validly existing as a corporation in good standing under the
laws of the State of Delaware. The Company has the corporate power and authority
to own, lease and operate its properties and to conduct its business as
currently conducted and to enter into and perform its obligations under this
Agreement. The Company is duly qualified as a foreign corporation to transact
business and is in good standing in each jurisdiction in which such
qualification is required, whether by reason of the ownership or leasing of
property or the conduct of business, except where the failure to so qualify
would not, singly or in the aggregate, have a material adverse effect on the
condition, financial or otherwise, or the earnings, assets, business affairs or
business prospects of the Company.

                  4.2 Capitalization.

                           (a) The authorized capital stock of the Company
consists of 75,000,000 shares of Common Stock and 25,000,000 shares of Preferred
Stock.

                           (b) As of December 31, 2000, the issued and
outstanding capital stock of the Company consists of 34,075,158 shares of Common
Stock. The shares of issued and outstanding capital stock of the Company have
been duly authorized and validly issued, are fully paid and nonassessable and
have not been issued in violation of or are not otherwise subject to any
preemptive or other similar rights.

                           (c) As of December 31, 2000, the Company has reserved
6,151,453 shares of Common Stock for issuance upon the exercise of stock options
granted or available for future grant under the Company's stock option plan.

                           (d) As of December 31, 2000, the Company has reserved
approximately 1,165,592 shares of Common Stock for issuance upon the exercise of
outstanding warrants to purchase Common Stock.

                           (e) As of December 31, 2000, the Company has reserved
304,019 shares of Common Stock for purchase under the Employee Stock Purchase
Plan.

         With the exception of the foregoing, there are no outstanding
subscriptions, options, warrants, convertible or exchangeable securities or
other rights granted to or by the Company to


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purchase shares of Common Stock or other securities of the Company and there are
no commitments, plans or arrangements to issue any shares of Common Stock or any
security convertible into or exchangeable for Common Stock.

                  4.3 Issuance, Sale and Delivery of the Shares.

                           (a) The Shares have been duly authorized for issuance
and sale to the Purchasers pursuant to this Agreement and, when issued and
delivered by the Company pursuant to this Agreement against payment of the
consideration set forth in this Agreement, will be validly issued and fully paid
and nonassessable and free and clear of all pledges, liens and encumbrances. The
Certificates evidencing the Shares are in due and proper form under Delaware
law.

                           (b) The issuance of the Shares is not subject to
preemptive or other similar rights. No further approval or authority of the
stockholders or the Board of Directors of the Company will be required for the
issuance and sale of the Shares to be sold by the Company as contemplated in
this Agreement.

                           (c) Subject to the accuracy of the Purchasers'
representations and warranties in Section 5 of this Agreement, the offer, sale,
and issuance of the Shares in conformity with the terms of this Agreement
constitute transactions exempt from the registration requirements of Section 5
of the Securities Act and from the registration or qualification requirements of
the laws of any applicable state or United States jurisdiction.

                  4.4 Financial Statements. The financial statements included
(as exhibits or otherwise) in the Company Documents (as defined below) present
fairly the financial position of the Company as of the dates indicated and the
results of their operations for the periods specified. Except as otherwise
stated in such Company Documents, such financial statements have been prepared
in conformity with generally accepted accounting principles applied on a
consistent basis, and any supporting schedules included with the financial
statements present fairly the information stated in the financial statements.
The financial and statistical data set forth in the Company Documents were
prepared on an accounting basis consistent with such financial statements.

                  4.5 No Material Change. Since September 30, 2000, the Company
has not incurred any material liabilities, direct or contingent, except in the
ordinary course of business, and

                           (a) there has been no material adverse change in the
financial condition or in the earnings, assets or business affairs of the
Company, whether or not arising in the ordinary course of business;

                           (b) except as set forth in the Schedule of Exceptions
as attached hereto as Exhibit B or otherwise publicly disclosed by the Company,
there have been no transactions entered into by the Company other than those in
the ordinary course of business, which are material with respect to the Company;


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                           (c) there has been no dividend or distribution of any
kind declared, paid or made by the Company on any class of its capital stock;
and

                           (d) there has not been any change in the capital
stock of the Company other than the sale of the Shares hereunder and shares or
options issued pursuant to employee equity incentive plans or purchase plans, or
indebtedness material to the Company (other than in the ordinary course of
business).

         Except as disclosed in the Company Documents (as defined in Section
4.26 below), the Company has no material contingent obligations.

                  4.6 Environmental. Except as would not, singly or in the
aggregate, reasonably be expected to have a material adverse effect on the
financial condition or in the earnings, assets or business affairs of the
Company,

                           (a) the Company is in compliance with all applicable
Environmental Laws (as defined below);

                           (b) the Company has all permits, authorizations and
approvals required under any applicable Environmental Laws and is in compliance
with the requirements of such permits authorizations and approvals;

                           (c) there are no pending or, to the best knowledge of
the Company, threatened Environmental Claims (as defined below) against the
Company; and

                           (d) under applicable law, there are no circumstances
with respect to any property or operations of the Company that are reasonably
likely to form the basis of an Environmental Claim against the Company.

         For purposes of this Agreement, the following terms shall have the
following meanings: "Environmental Law" means any United States (or other
applicable jurisdiction's) Federal, state, local or municipal statute, law,
rule, regulation, ordinance, code, policy or rule of common law and any judicial
or administrative interpretation thereof, including any judicial or
administrative order, consent decree or judgment, relating to the environment,
health, safety or any chemical, material or substance, exposure to which is
prohibited, limited or regulated by any governmental authority. "Environmental
Claims" means any and all administrative, regulatory or judicial actions, suits,
demands, demand letters, claims, liens, notices of noncompliance or violation,
investigations or proceedings relating in any way to any Environmental Law.

                  4.7 No Defaults. The Company is not in violation of its
certificate of incorporation or bylaws or in material default in the performance
or observance of any obligation, agreement, covenant or condition contained in
any material contract, indenture, mortgage, loan agreement, deed, trust, note,
lease, sublease, voting agreement, voting trust, or other instrument or material
agreement to which the Company is a party or by which it may be bound, or to
which any of the property or assets of the Company is subject.


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                  4.8 Labor Matters. No labor dispute with the employees of the
Company exists or, to the best knowledge of the Company, is imminent.

                  4.9 No Actions. Except as set forth in the Schedule of
Exceptions as attached hereto as Exhibit B or otherwise publicly disclosed by
the Company, there is no action, suit or proceeding before or by any court or
governmental agency or body, domestic or foreign, now pending, or, to the
knowledge of the Company, threatened, against or affecting the Company which,
singly or in the aggregate, might result in any material adverse change in the
condition, financial or otherwise, or in the earnings, business affairs or
business prospects of the Company, or which, singly or in the aggregate, might
materially and adversely affect the properties or assets thereof or which might
materially and adversely affect the consummation of this Agreement, nor, to the
best knowledge of the Company, is there any reasonable basis therefor. The
Company is not in default with respect to any judgment, order or decree of any
court or governmental agency or instrumentality which, singly or in the
aggregate, would have a material adverse effect on the assets, properties or
business of the Company.

                  4.10 Intellectual Property.

                           (a) The Company, to the best of its knowledge in the
course of diligent inquiry, owns or is licensed to use all patents, patent
applications, inventions, trademarks, trade names, applications for registration
of trademarks, service marks, service mark applications, copyrights, know-how,
manufacturing processes, formulae, trade secrets, licenses and rights in any
thereof and any other intangible property and assets that are material to the
business of the Company as now conducted and as proposed to be conducted (in
this Agreement called the "Proprietary Rights"), or is seeking, or will seek, to
obtain rights to use such Proprietary Rights that are material to the business
of the Company as proposed to be conducted.

                           (b) Except as set forth in the Schedule of Exceptions
as attached hereto as Exhibit B or otherwise publicly disclosed by the Company,
the Company does not have any knowledge of, and the Company has not given or
received any notice of, any pending conflicts with or infringement of the rights
of others with respect to any Proprietary Rights or with respect to any license
of Proprietary Rights which are material to the business of the Company.

                           (c) Except as set forth in the Schedule of Exceptions
as attached hereto as Exhibit B or otherwise publicly disclosed by the Company,
no action, suit, arbitration, or legal, administrative or other proceeding, or
investigation is pending, or, to the best knowledge of the Company, threatened,
which involves any Proprietary Rights, nor, to the best knowledge of the
Company, is there any reasonable basis therefor.

                           (d) The Company is not subject to any judgment,
order, writ, injunction or decree of any court or any Federal, state, local,
foreign or other governmental department, commission, board, bureau, agency or
instrumentality, domestic or foreign, or any arbitrator, and has not entered
into or is not a party to any contract which restricts or impairs the use of any
such Proprietary Rights in a manner which would have a material adverse effect
on the use of any of the Proprietary Rights.


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                           (e) Except as set forth in the Schedule of Exceptions
as attached hereto as Exhibit B or otherwise publicly disclosed by the Company,
the Company has not received written notice of any pending conflict with or
infringement upon such third-party proprietary rights.

                           (f) The Company has not entered into any consent,
indemnification, forbearance to sue or settlement agreement with respect to
Proprietary Rights other than in the ordinary course of business. No claims have
been asserted by any person with respect to the validity of the Company's
ownership or right to use the Proprietary Rights and, to the best knowledge of
the Company, there is no reasonable basis for any such claim to be successful.

                           (g) The Company has complied, in all material
respects, with its obligations relating to the protection of the Proprietary
Rights which are material to the business of the Company used pursuant to
licenses.

                           (h) To the best knowledge of the Company, no person
is infringing on or violating the Proprietary Rights.

                  4.11 Permits. The Company possesses and is operating in
compliance with all material licenses, certificates, consents, authorities,
approvals and permits from all state, federal, foreign and other regulatory
agencies or bodies necessary to conduct the businesses now operated by it, and
the Company has not received any notice of proceedings relating to the
revocation or modification of any such permit or any circumstance which would
lead it to believe that such proceedings are reasonably likely which, singly or
in the aggregate, if the subject of an unfavorable decision, ruling or finding,
would materially and adversely affect the condition, financial or otherwise, or
the earnings, assets, business affairs or business prospects of the Company.

                  4.12 Due Execution, Delivery and Performance. This Agreement
has been duly executed and delivered by the Company and constitutes a valid and
binding obligation of the Company, enforceable against the Company in accordance
with its terms. The execution, delivery and performance of this Agreement and
the consummation of the transactions contemplated in this Agreement and the
fulfillment of the terms of this Agreement have been duly authorized by all
necessary corporate action and will not conflict with or constitute a breach of,
or default under, or result in the creation or imposition of any lien, charge or
encumbrance upon any property or assets of the Company pursuant to, any
contract, indenture, mortgage, loan agreement, deed, trust, note, lease,
sublease, voting agreement, voting trust or other instrument or agreement to
which the Company is a party or by which it may be bound, or to which any of the
property or assets of the Company is subject, and will not trigger anti-dilution
rights or other rights to acquire additional equity securities of the Company,
nor will such action result in any violation of the provisions of the articles
of incorporation or bylaws of the Company or any applicable statute, law, rule,
regulation, ordinance, decision, directive or order.

                  4.13 Properties. The Company has good and marketable title to
its properties, free and clear of all material security interests, mortgages,
pledges, liens, charges, encumbrances and claims of record. The properties of
the Company are, in the aggregate, in good repair (reasonable wear and tear
excepted), and suitable for their respective uses. To the Company's knowledge,
any


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real property held under lease by the Company is held under valid, subsisting
and enforceable leases with such exceptions as are not material and do not
interfere with the conduct of the business of the Company. The Company owns or
leases all such properties as are necessary to its business or operations as now
conducted.

                  4.14 Compliance. The Company has conducted and is conducting
its business in compliance with all applicable Federal, state, local and foreign
statutes, laws, rules, regulations, ordinances, codes, decisions, decrees,
directives and orders, except where the failure to do so would not, singly or in
the aggregate, have a material adverse effect on the condition, financial or
otherwise, or on the earnings, assets, business affairs or business prospects of
the Company.

                  4.15 Security Measures. The Company takes security measures
designed to enable the Company to assert trade secret protection in its
non-patented technology.

                  4.16 Contributions. To the best of the Company's knowledge,
neither the Company nor any employee or agent of the Company has made any
payment of funds of the Company or received or retained any funds in violation
of any law, rule or regulation.

                  4.17 Use of Proceeds; Investment Company. The Company intends
to use the proceeds from the sale of the Shares for working capital and other
general corporate purposes. The Company is not now, and after the sale of the
Shares under this Agreement and under all other agreements and the application
of the net proceeds from the sale of the Shares described in the proceeding
sentence will not be, an "investment company" within the meaning of the
Investment Company Act of 1940, as amended.

                  4.18 Prior Offerings. All offers and sales of capital stock of
the Company before the date of this Agreement were at all relevant times duly
registered or exempt from the registration requirements of the Securities Act
and were duly registered or subject to an available exemption from the
registration requirements of the applicable state securities or Blue Sky laws.

                  4.19 Taxes. The Company has filed all material tax returns
required to be filed, which returns are true and correct in all material
respects, and the Company is not in default in the payment of any taxes,
including penalties and interest, assessments, fees and other charges, shown
thereon due or otherwise assessed, other than those being contested in good
faith and for which adequate reserves have been provided or those currently
payable without interest which were payable pursuant to said returns or any
assessments with respect thereto.

                  4.20 Other Governmental Proceedings. To the Company's
knowledge, there are no rulemaking or similar proceedings before any Federal,
state, local or foreign government bodies that involve or affect the Company,
which, if the subject of an action unfavorable to the Company, could involve a
prospective material adverse change in or effect on the condition, financial or
otherwise, or in the earnings, assets, business affairs or business prospects of
the Company.

                  4.21 Non-Competition Agreements. To the knowledge of the
Company, any full-time employee who has entered into any non-competition,
non-disclosure, confidentiality or other


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similar agreement with any party other than the Company is neither in violation
of nor is expected to be in violation of that agreement as a result of the
business currently conducted or expected to be conducted by the Company or such
person's performance of his or her obligations to the Company. The Company has
not received written notice that any consultant or scientific advisor of the
Company is in violation of any non-competition, non-disclosure, confidentiality
or similar agreement.

                  4.22 Transfer Taxes. On the Closing Date, all stock transfer
or other taxes (other than income taxes) that are required to be paid in
connection with the sale and transfer of the Shares to be sold to the Purchasers
under this Agreement will be, or will have been, fully paid or provided for by
the Company and all laws imposing such taxes will be or will have been fully
complied with.

                  4.23 Insurance. The Company maintains insurance of the type
and in the amount that the Company reasonably believes is adequate for its
business, including, but not limited to, insurance covering all real and
personal property owned or leased by the Company against theft, damage,
destruction, acts of vandalism and all other risks customarily insured against
by similarly situated companies, all of which insurance is in full force and
effect.

                  4.24 Governmental Consents. No registration, authorization,
approval, qualification or consent of any court or governmental authority or
agency is necessary in connection with the execution and delivery of this
Agreement or the offering, issuance or sale of the Shares under this Agreement,
other than any filings required by a Purchaser under the Hart-Scott-Rodino
Antitrust Improvement Act of 1976.

                  4.25 Securities and Exchange Commission Filings. The Company
has timely filed with the Securities and Exchange Commission (the "Commission")
all documents required to be filed by the Company under the Exchange Act of
1934, as amended (the "Exchange Act.")

                  4.26 Additional Information. The Company represents and
warrants that the information contained in the following documents (the "Company
Documents"), which has been made available to Purchaser before the Closing, is
or will be true and correct in all material respects as of their respective
final dates:

                           (a) the Company's Annual Report on Form 10-K for the
fiscal year ended December 31, 1999;

                           (b) the Company's Quarterly Reports on Form 10-Q for
the fiscal quarters ended March 31, 2000, June 30, 2000 and September 30, 2000;

                           (c) the Company's Proxy Statement for its 2000 Annual
Meeting of Stockholders; and

                           (d) all other documents, if any, filed by the Company
with the Commission since September 30, 2000 pursuant to the reporting
requirements of the Securities Exchange Act.


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                  4.27 Contracts. The contracts described in the Company
Documents or incorporated by reference therein are in full force and effect on
the date hereof, except for contracts the termination or expiration of which
would not, singly or in the aggregate, have a material adverse effect on the
business, properties or assets of the Company. Neither the Company nor, to the
best knowledge of the Company, any other party is in material breach of or
default under any such contracts.

                  4.28 No Integrated Offering. Neither the Company, nor any of
its affiliates, nor any person acting on its or their behalf, has directly or
indirectly made any offers or sales in any security or solicited any offers to
buy any security under circumstances that would require registration under the
Securities Act of the issuance of the Shares to the Purchasers. The issuance of
the Shares to the Purchasers will not be integrated with any other issuance of
the Company's securities (past, current or future) for purposes of the
Securities Act or any applicable rules of Nasdaq. The Company will not make any
offers or sales of any security (other than the Shares) that would cause the
offering of the Shares to be integrated with any other offering of securities by
the Company for purposes of any registration requirement under the Securities
Act or any applicable rules of Nasdaq.

                  4.29 Real Property Holding Corporation. The Company is not a
real property holding corporation within the meaning of Internal Revenue Code
Section 897(c)(2) and any regulations promulgated thereunder.

         5. Representations, Warranties and Covenants of the Purchasers.

                  5.1 Securities Law Representations and Warranties. Each
Purchaser represents, warrants and covenants to the Company as follows:

                           (a) The Purchaser is knowledgeable, sophisticated and
experienced in making, and is qualified to make, decisions with respect to
investments in shares representing an investment decision like that involved in
the purchase of the Shares, including investments in securities issued by the
Company, and has requested, received, reviewed and considered all information it
deems relevant in making an informed decision to purchase the Shares.

                           (b) With the exception of Lombard Odier & Cie
("Lombard") which makes separate representations below, the Purchaser is
acquiring the number of Shares set forth in Section 2 above in the ordinary
course of its business and for its own account for investment (as defined for
purposes of the Hart-Scott-Rodino Antitrust Improvement Act of 1976 and the
regulations thereunder) only, and has no present intention of distributing any
of the Shares nor any arrangement or understanding with any other persons
regarding the distribution of such Shares within the meaning of Section 2(11) of
the Securities Act, or as contemplated in Section 7 of this Agreement.

                           (c) The Purchaser will not, directly or indirectly,
offer, sell, pledge, transfer or otherwise dispose of (or solicit any offers to
buy, purchase or otherwise acquire or take a


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<PAGE>   11


pledge of) any of the Shares except in compliance with the Securities Act and
the Rules and Regulations.

                           (d) The Purchaser has completed or caused to be
completed the Stock Certificate Questionnaire and the Registration Statement
Questionnaire, attached to this Agreement as Appendices I and II, for use in
preparation of the Registration Statement (as defined in Section 7.3 below), and
the answers to the Questionnaires are true and correct as of the date of this
Agreement and will be true and correct as of the effective date of the
Registration Statement; provided that the Purchasers shall be entitled to update
such information by providing notice thereof to the Company before the effective
date of such Registration Statement.

                           (e) The Purchaser has, in connection with its
decision to purchase the number of Shares set forth in Section 2 above, relied
solely upon the Company Documents and the representations and warranties of the
Company contained in this Agreement.

                           (f) With the exception of Lombard which makes
separate representations below, the Purchaser is an "accredited investor" within
the meaning of Rule 501 of Regulation D promulgated under the Securities Act.

                           (g) Separate representations of Lombard:

                                    (i) Lombard is acquiring the number of
Shares set forth in Section 2 above in the ordinary course of its business for
its account, the account of the Lombard Odier Immunology Fund ("LOIF"), or for
the account of its clients for investment (as defined for purposes of the
Hart-Scott-Rodino Antitrust Improvement Act of 1976 and the regulations
thereunder) only, and has no present intention of distributing any of the Shares
other than as contemplated in Section 7 if this Agreement. Lombard's clients
have represented to Lombard that such clients are acquiring the Shares for
investment only, and with no present intention of distributing any of the Shares
other than as contemplated in Section 7 of this Agreement.

                                    (ii) Lombard represents that it, LOIF, and
any of its clients to which it attributes the Shares is an "accredited investor"
within the meaning of Rule 501 of Regulation D promulgated under the Securities
Act.

                  5.2 Resales of Shares.

                           (a) The Purchaser hereby covenants with the Company
not to make any sale of the Shares without satisfying the requirements of the
Securities Act and the Rules and Regulations, including, in the event of any
resale under the Registration Statement, the prospectus delivery requirements
under the Securities Act, and the Purchaser acknowledges and agrees that such
Shares are not transferable on the books of the Company pursuant to a resale
under the Registration Statement unless the certificate submitted to the
transfer agent evidencing the Shares is accompanied by a separate officer's
certificate

                                    (i) in the form of Appendix III to this
Agreement;


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                                    (ii) executed by an officer of, or other
authorized person designated by, the Purchaser; and

                                    (iii) to the effect that (A) the Shares have
been sold in accordance with the Registration Statement and (B) the requirement
of delivering a current prospectus has been satisfied.

                           (b) The Purchaser acknowledges that there may
occasionally be times when the Company determines, in good faith following
consultation with its board of directors or a committee thereof, the use of the
prospectus forming a part of the Registration Statement (the "Prospectus," as
further defined in Section 7.3.1 below) should be suspended until such time as
an amendment or supplement to the Registration Statement or the Prospectus has
been filed by the Company and any such amendment to the Registration Statement
is declared effective by the Commission, or until such time as the Company has
filed an appropriate report with the Commission pursuant to the Exchange Act.
The Purchaser hereby covenants that it will not sell any Shares pursuant to the
Prospectus during the period commencing at the time at which the Company gives
the Purchaser written notice of the suspension of the use of the Prospectus and
ending at the time the Company gives the Purchaser written notice that the
Purchaser may thereafter effect sales pursuant to the Prospectus. The Company
may, upon written notice to the Purchasers, suspend the use of the Prospectus
for up to thirty (30) days in any 365-day period based on the reasonable
determination of the Company's Board of Directors that there is a significant
business purpose for such determination, such as pending corporate developments,
public filings with the SEC or similar events. The Company shall in no event be
required to disclose the business purpose for which it has suspended the use of
the Prospectus if the Company determines in its good faith judgment that the
business purpose should remain confidential. In addition, the Company shall
notify each Purchaser (i) of any request by the SEC for an amendment or any
supplement to such Registration Statement or any related prospectus, or any
other information request by any other governmental agency directly relating to
the offering, and (ii) of the issuance by the SEC of any stop order suspending
the effectiveness of such Registration Statement or of any order preventing or
suspending the use of any related prospectus or the initiation or threat of any
proceeding for that purpose.

                           (c) The Purchaser further covenants to notify the
Company promptly of the sale of any of its Shares, other than sales pursuant to
a Registration Statement contemplated in Section 7 of this Agreement or sales
upon termination of the transfer restrictions pursuant to Section 7.4 of this
Agreement.

                  5.3 Due Execution, Delivery and Performance.

                           (a) This Agreement has been duly executed and
delivered by the Purchaser and constitutes a valid and binding obligation of the
Purchaser, enforceable against the Purchaser in accordance with its terms.

                           (b) The execution, delivery and performance of this
Agreement and the consummation of the transactions contemplated in this
Agreement and the fulfillment of the terms of this Agreement have been duly
authorized by all necessary corporate action and will not conflict


                                      -12-
<PAGE>   13


with or constitute a breach of, or default under, or result in the creation or
imposition of any lien, charge or encumbrance upon any property or assets of the
Purchaser pursuant to, any contract, indenture, mortgage, loan agreement, deed,
trust, note, lease, sublease, voting agreement, voting trust or other instrument
or agreement to which the Purchaser is a party or by which it or any of them may
be bound, or to which any of the property or assets of the Purchaser is subject,
nor will such action result in any violation of the provisions of the charter or
bylaws of the Purchaser or any applicable statute, law, rule, regulation,
ordinance, decision, directive or order.

         6. Survival of Representations, Warranties and Agreements.
Notwithstanding any investigation made by any party to this Agreement, all
covenants, agreements, representations and warranties made by the Company and
the Purchasers in this Agreement and in the certificates for the Shares
delivered pursuant to this Agreement shall survive the execution of this
Agreement, the delivery to the Purchasers of the Shares being purchased and the
payment therefor.

         7. Form D Filing; Registration; Compliance with the Securities Act;
Covenants.

                  7.1 Form D Filing; Registration of Shares.

                           7.1.1 Registration Statement; Expenses. The Company
shall:

                                    (a) file in a timely manner a Form D
relating to the sale of the Shares under this Agreement, pursuant to Securities
and Exchange Commission Regulation D.

                                    (b) as soon as practicable after the Closing
Date, but in no event later than the 20th day following the Closing Date,
prepare and file with the Commission a Registration Statement on Form S-3 (or,
if the Company is ineligible to use Form S-3, then on Form S-1) relating to the
sale of the Shares by the Purchasers from time to time on the Nasdaq National
Market (or the facilities of any national securities exchange on which the
Company's Common Stock is then traded) or in privately negotiated transactions
(the "Registration Statement");

                                    (c) provide to Purchasers any information
required to permit the sale of the Shares under rule 144A of the Securities Act;

                                    (d) subject to receipt of necessary
information from the Purchasers, use its best efforts to cause the Commission to
notify the Company of the Commission's willingness to declare the Registration
Statement effective on or before 90 days after the Closing Date;

                                    (e) notify Purchasers promptly upon the
Registration Statement, or any post-effective amendment thereto, being declared
effective by the Commission;

                                    (f) prepare and file with the Commission
such amendments and supplements to the Registration Statement and the Prospectus
(as defined in Section 7.3.1 below) and take such other action, if any, as may
be necessary to keep the Registration Statement effective until the earlier of
(i) two years after the effective date of the Registration Statement, (ii) the
date on


                                      -13-
<PAGE>   14


which the Shares may be resold by the Purchasers without registration or without
regard to any volume limitations by reason of Rule 144(k) under the Securities
Act or any other rule of similar effect or (iii) all of the Shares have been
sold pursuant to the Registration Statement or Rule 144(k) under the Securities
Act or any other rule of similar effect;

                                    (g) promptly furnish to the Purchasers with
respect to the Shares registered under the Registration Statement such
reasonable number of copies of the Prospectus, including any supplements to or
amendments of the Prospectus, in order to facilitate the public sale or other
disposition of all or any of the Shares by the Purchasers;

                                    (h) during the period when copies of the
Prospectus are required to be delivered under the Securities Act or the Exchange
Act, will file all documents required to be filed with the Commission pursuant
to Section 13, 14 or 15 of the Exchange Act within the time periods required by
the Exchange Act and the rules and regulations promulgated thereunder;

                                    (i) file documents required of the Company
for customary Blue Sky clearance in all states requiring Blue Sky clearance;
provided, however, that the Company shall not be required to qualify to do
business or consent to service of process in any jurisdiction in which it is not
now so qualified or has not so consented; and

                                    (j) bear all expenses in connection with the
procedures in paragraphs (a) through (f) of this Section 7.1.1 and the
registration of the Shares pursuant to the Registration Statement, including
fees and expenses (whether external or internal) of up to $15,000 of the
Purchaser, but not including any fees and expenses of any other advisers to the
Purchasers or brokerage fees and commissions incurred by the Purchasers.

                           7.1.2 Delay in Effectiveness of Registration
Statement. In the event that the Registration Statement is not declared
effective by the date that is 120 days after the Closing Date, the Company shall
pay to each Purchaser liquidated damages in an amount equal to 0.25% of the
total purchase price of the Shares purchased by such Purchaser pursuant to this
Agreement for each week after by the date that is 120 days after the Closing
Date that the Registration Statement is not declared effective.

                  7.2 Transfer of Shares After Registration. Each Purchaser
agrees that it will not effect any disposition of the Shares or its right to
purchase the Shares that would constitute a sale within the meaning of the
Securities Act, except as contemplated in the Registration Statement referred to
in Section 7.1 or as otherwise permitted by law, and that it will promptly
notify the Company of any changes in the information set forth in the
Registration Statement regarding the Purchaser or its plan of distribution.

                  7.3 Indemnification. For the purpose of this Section 7.3, the
term "Registration Statement" shall include any preliminary or final prospectus,
exhibit, supplement or amendment included in or relating to the Registration
Statement referred to in Section 7.1.


                                      -14-
<PAGE>   15


                           7.3.1 Indemnification by the Company. The Company
agrees to indemnify and hold harmless each of the Purchasers and each person, if
any, who controls any Purchaser within the meaning of the Securities Act,
against any losses, claims, damages, liabilities or expenses, joint or several,
to which such Purchasers or such controlling person may become subject, under
the Securities Act, the Exchange Act, or any other federal or state statutory
law or regulation, or at common law or otherwise (including in settlement of any
litigation, if such settlement is effected with the written consent of the
Company, which consent shall not be unreasonably withheld), insofar as such
losses, claims, damages, liabilities or expenses (or actions in respect thereof
as contemplated below) arise out of or are based upon any untrue statement or
alleged untrue statement of any material fact contained in the Registration
Statement, including the Prospectus, financial statements and schedules, and all
other documents filed as a part thereof, as amended at the time of effectiveness
of the Registration Statement, including any information deemed to be a part
thereof as of the time of effectiveness pursuant to paragraph (b) of Rule 430A,
or pursuant to Rule 434, of the Rules and Regulations, or the Prospectus, in the
form first filed with the Commission pursuant to Rule 424(b) of the Regulations,
or filed as part of the Registration Statement at the time of effectiveness if
no Rule 424(b) filing is required (the "Prospectus"), or any amendment or
supplement thereto, or arise out of or are based upon the omission or alleged
omission to state in any of them a material fact required to be stated therein
or necessary to make the statements in any of them, in light of the
circumstances under which they were made, not misleading, or arise out of or are
based in whole or in part on any inaccuracy in the representations and
warranties of the Company contained in this Agreement, or any failure of the
Company to perform its obligations under this Agreement or under law, and will
reimburse each Purchaser and each such controlling person for any legal and
other expenses as such expenses are reasonably incurred by such Purchaser or
such controlling person in connection with investigating, defending, settling,
compromising or paying any such loss, claim, damage, liability, expense or
action; provided, however, that the Company will not be liable in any such case
to the extent that any such loss, claim, damage, liability or expense arises out
of or is based upon (i) an untrue statement or alleged untrue statement or
omission or alleged omission made in the Registration Statement, the Prospectus
or any amendment or supplement of the Registration Statement or Prospectus in
reliance upon and in conformity with written information furnished to the
Company by or on behalf of the Purchaser expressly for use in the Registration
Statement or the Prospectus, or (ii) the failure of such Purchaser to comply
with the covenants and agreements contained in Sections 5.2 or 7.2 of this
Agreement respecting resale of the Shares, or (iii) the inaccuracy of any
representations made by such Purchaser in this Agreement or (iv) any untrue
statement or omission of a material fact required to make such statement not
misleading in any Prospectus that is corrected in any subsequent Prospectus that
was delivered to the Purchaser before the pertinent sale or sales by the
Purchaser.

                           7.3.2 Indemnification by the Purchaser. Each
Purchaser will severally and not jointly indemnify and hold harmless the
Company, each of its directors, each of its officers who signed the Registration
Statement and each person, if any, who controls the Company within the meaning
of the Securities Act, against any losses, claims, damages, liabilities or
expenses to which the Company, each of its directors, each of its officers who
signed the Registration Statement or controlling person may become subject,
under the Securities Act, the Exchange Act, or any other federal or state
statutory law or regulation, or at common law or otherwise (including in
settlement


                                      -15-
<PAGE>   16


of any litigation, if such settlement is effected with the written consent of
such Purchaser, which consent shall not be unreasonably withheld) insofar as
such losses, claims, damages, liabilities or expenses (or actions in respect
thereof as contemplated below) arise out of or are based upon (i) any failure on
the part of such Purchaser to comply with the covenants and agreements contained
in Sections 5.2 or 7.2 of this Agreement respecting the sale of the Shares or
(ii) the inaccuracy of any representation made by such Purchaser in this
Agreement or (iii) any untrue or alleged untrue statement of any material fact
contained in the Registration Statement, the Prospectus, or any amendment or
supplement to the Registration Statement or Prospectus, or arise out of or are
based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, in each case to the extent, but only to the extent, that such untrue
statement or alleged untrue statement or omission or alleged omission was made
in the Registration Statement, the Prospectus, or any amendment or supplement
thereto, in reliance upon and in conformity with written information furnished
to the Company by or on behalf of such Purchaser expressly for use therein;
provided, however, that the Purchaser shall not be liable for any such untrue or
alleged untrue statement or omission or alleged omission of which the Purchaser
has delivered to the Company in writing a correction before the occurrence of
the transaction from which such loss was incurred, and the Purchaser will
reimburse the Company, each of its directors, each of its officers who signed
the Registration Statement or controlling person for any legal and other expense
reasonably incurred by the Company, each of its directors, each of its officers
who signed the Registration Statement or controlling person in connection with
investigating, defending, settling, compromising or paying any such loss, claim,
damage, liability, expense or action.

                           7.3.3 Indemnification Procedure.

                                    (a) Promptly after receipt by an indemnified
party under this Section 7.3 of notice of the threat or commencement of any
action, such indemnified party will, if a claim in respect thereof is to be made
against an indemnifying party under this Section 7.3, promptly notify the
indemnifying party in writing of the claim; but the omission so to notify the
indemnifying party will not relieve it from any liability which it may have to
any indemnified party for contribution or otherwise under the indemnity
agreement contained in this Section 7.3 or to the extent it is not prejudiced as
a result of such failure.

                                    (b) In case any such action is brought
against any indemnified party and such indemnified party seeks or intends to
seek indemnity from an indemnifying party, the indemnifying party will be
entitled to participate in, and, to the extent that it may wish, jointly with
all other indemnifying parties similarly notified, to assume the defense thereof
with counsel reasonably satisfactory to such indemnified party; provided,
however, if the defendants in any such action include both the indemnified party
and the indemnifying party and the indemnified party shall have reasonably
concluded that there may be a conflict between the positions of the indemnifying
party and the indemnified party in conducting the defense of any such action or
that there may be legal defenses available to it or other indemnified parties
that are different from or additional to those available to the indemnifying
party, the indemnified party or parties shall have the right to select separate
counsel to assume such legal defenses and to otherwise participate in the
defense of


                                      -16-
<PAGE>   17


such action on behalf of such indemnified party or parties. Upon receipt of
notice from the indemnifying party to such indemnified party of its election so
to assume the defense of such action and approval by the indemnified party of
counsel, the indemnifying party will not be liable to such indemnified party
under this Section 7.3 for any legal or other expenses subsequently incurred by
such indemnified party in connection with the defense thereof unless:

                                             (i) the indemnified party shall
have employed such counsel in connection with the assumption of legal defenses
in accordance with the proviso to the preceding sentence (it being understood,
however, that the indemnifying party shall not be liable for the expenses of
more than one separate counsel, approved by such indemnifying party representing
all of the indemnified parties who are parties to such action) or

                                             (ii) the indemnifying party shall
not have employed counsel reasonably satisfactory to the indemnified party to
represent the indemnified party within a reasonable time after notice of
commencement of action, in each of which cases the reasonable fees and expenses
of counsel shall be at the expense of the indemnifying party. Notwithstanding
the provisions of this Section 7.3, the Purchaser shall not be liable for any
indemnification obligation under this Agreement in excess of the amount of gross
proceeds received by the Purchaser from the sale of the Shares.

                           7.3.4 Contribution. If the indemnification provided
for in this Section 7.3 is required by its terms but is for any reason held to
be unavailable to or otherwise insufficient to hold harmless an indemnified
party under this Section 7.3 in respect to any losses, claims, damages,
liabilities or expenses referred to in this Agreement, then each applicable
indemnifying party shall contribute to the amount paid or payable by such
indemnified party as a result of any losses, claims, damages, liabilities or
expenses referred to in this Agreement

                                    (a) in such proportion as is appropriate to
reflect the relative benefits received by the Company and the Purchaser from the
placement of Common Stock or

                                    (b) if the allocation provided by clause (a)
above is not permitted by applicable law, in such proportion as is appropriate
to reflect not only the relative benefits referred to in clause (a) above but
the relative fault of the Company and the Purchaser in connection with the
statements or omissions or inaccuracies in the representations and warranties in
this Agreement that resulted in such losses, claims, damages, liabilities or
expenses, as well as any other relevant equitable considerations.

         The respective relative benefits received by the Company on the one
hand and each Purchaser on the other shall be deemed to be in the same
proportion as the amount paid by such Purchaser to the Company pursuant to this
Agreement for the Shares purchased by such Purchaser that were sold pursuant to
the Registration Statement bears to the difference (the "Difference") between
the amount such Purchaser paid for the Shares that were sold pursuant to the
Registration Statement and the amount received by such Purchaser from such sale.
The relative fault of the Company and each Purchaser shall be determined by
reference to, among other things, whether the untrue or alleged statement of a
material fact or the omission or alleged omission to state a material


                                      -17-
<PAGE>   18


fact or the inaccurate or the alleged inaccurate representation or warranty
relates to information supplied by the Company or by such Purchaser 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, subject to the limitations set
forth in Section 7.3.3, any legal or other fees or expenses reasonably incurred
by such party in connection with investigating or defending any action or claim.
The provisions set forth in Section 7.3.3 with respect to the notice of the
threat or commencement of any threat or action shall apply if a claim for
contribution is to be made under this Section 7.3.4; provided, however, that no
additional notice shall be required with respect to any threat or action for
which notice has been given under Section 7.3 for purposes of indemnification.
The Company and each Purchaser agree that it would not be just and equitable if
contribution pursuant to this Section 7.3 were determined solely by pro rata
allocation (even if the Purchaser were treated as one entity for such purpose)
or by any other method of allocation which does not take account of the
equitable considerations referred to in this paragraph. Notwithstanding the
provisions of this Section 7.3, no Purchaser shall be required to contribute any
amount in excess of the amount by which the Difference exceeds the amount of any
damages that such Purchaser has otherwise been required to pay by reason of such
untrue or alleged untrue statement or omission or alleged omission. 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. The Purchasers' obligations to
contribute pursuant to this Section 7.3 are several and not joint.

                  7.4 Termination of Conditions and Obligations. The
restrictions imposed by Section 5 or this Section 7 upon the transferability of
the Shares shall cease and terminate as to any particular number of the Shares
upon the passage of two years from the Closing Date or at such time as an
opinion of counsel satisfactory in form and substance to the Company shall have
been rendered to the effect that such conditions are not necessary in order to
comply with the Securities Act.

                  7.5 Information Available. So long as the Registration
Statement is effective covering the resale of Shares owned by any Purchaser, the
Company will furnish to such Purchaser:

                           (a) as soon as practicable after available (but in
the case of the Company's Annual Report to Stockholders, within 90 days after
the end of each fiscal year of the Company), one copy of

                                    (i) its Annual Report to Stockholders (which
Annual Report shall contain financial statements audited in accordance with
generally accepted accounting principles by a national firm of certified public
accountants);

                                    (ii) if not included in substance in the
Annual Report to Stockholders, its Annual Report on Form 10-K;

                                    (iii) if not included in substance in its
Quarterly Reports to Stockholders, its quarterly reports on Form 10-Q; and


                                      -18-
<PAGE>   19


                                    (iv) a full copy of the particular
Registration Statement covering the Shares (the foregoing, in each case,
excluding exhibits);

                           (b) upon the request of the Purchaser, a reasonable
number of copies of the Prospectus to supply to any other party requiring the
Prospectus.

                  7.6 Rule 144 Information. For two years after the date of this
Agreement, the Company shall file all reports required to be filed by it under
the Securities Act, the Rules and Regulations and the Exchange Act and shall
take such further action to the extent required to enable the Purchasers to sell
the Shares pursuant to Rule 144 under the Securities Act (as such rule may be
amended from time to time).

                  7.7 Prohibition of Issuance of Certain Toxic Securities. The
Company shall not sell or issue shares of Common Stock or any other security of
the Company convertible, exercisable or exchangeable into shares of Common
Stock, for a purchase, conversion, exercise or exchange price per share which is
subject to adjustment based on the market price of the Common Stock at the time
of conversion, exercise or exchange of such security into Common Stock, without
first consulting the five (5) holders who beneficially own the largest number of
shares of Common Stock immediately prior to the approval by the Company's Board
of Directors of such sale or issuance. The Company may rely exclusively upon the
filings with the Commission under the Exchange Act with respect to beneficial
ownership of its Common Stock and the identity of such holders.

         8. Advisory Fee. The Purchasers acknowledge that the Company intends to
pay to Wells Fargo Van Kasper, a financial advisor, a fee in respect of the sale
of the Shares. Each of the parties to this Agreement hereby represents that, on
the basis of any actions and agreements by it, there are no other brokers or
finders entitled to compensation in connection with the sale of the Shares to
the Purchasers. The Company shall indemnify and hold harmless the Purchasers
from and against all fees, commissions or other payments owing by the Company to
Wells Fargo Van Kasper or any other person or firm acting on behalf of the
Company hereunder.

         9. Notices. All notices, requests, consents and other communications
under this Agreement shall be in writing, shall be mailed by first-class
registered or certified airmail, confirmed facsimile or nationally recognized
overnight express courier postage prepaid, and shall be delivered as addressed
as follows:

                           (a)      if to the Company, to:

                                    Heska Corporation
                                    1613 Prospect Parkway
                                    Fort Collins, Colorado 80525
                                    Attn: Chief Financial Officer

                                    with a copy to:
                                    Karen A. Dempsey
                                    Wilson Sonsini Goodrich & Rosati, PC
                                    One Market Plaza
                                    Spear Street Tower
                                    Suite 3300
                                    San Francisco, California 94105


                                      -19-
<PAGE>   20


or to such other person at such other place as the Company shall designate to
the Purchaser in writing; and

                           (b) if to a Purchaser, at its address as set forth on
the signature page to this Agreement, or at such other address or addresses as
may have been furnished to the Company in writing.

         Such notice shall be deemed effectively given upon confirmation of
receipt by facsimile, two business days after deposit with such overnight
courier.

         10. Modification; Amendment. This Agreement may not be modified or
amended except pursuant to an instrument in writing signed by the Company and
the Purchasers of the Shares sold pursuant to this Agreement.

         11. Termination. This Agreement may be terminated as to any Purchaser,
at the option of such Purchaser, if the Closing has not occurred on or before
thirty (30) days from the date of this Agreement.

         12. Headings. The headings of the various sections of this Agreement
have been inserted for convenience of reference only and shall not be deemed to
be part of this Agreement.

         13. Severability. If any provision contained in this Agreement should
be held to be invalid, illegal or unenforceable in any respect, the validity,
legality and enforceability of the remaining provisions contained in this
Agreement shall not in any way be affected or impaired thereby.

         14. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the state of Delaware and the federal law of the
United States of America.

         15. Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall constitute an original, but all of which, when
taken together, shall constitute but one instrument, and shall become effective
when one or more counterparts have been signed by each party to this Agreement
and delivered to the other parties.

                            [Signature pages follow]


                                      -20-
<PAGE>   21


         IN WITNESS WHEREOF, the parties to this Agreement have caused this
Agreement to be executed by their duly authorized representatives as of the day
and year first above written.

                                        HESKA CORPORATION

                                        By: /s/ Ronald L. Hendrick
                                             ----------------------------------

                                        Name: Ronald L. Hendrick
                                             ----------------------------------

                                        Its: Executive Vice President and Chief
                                             ----------------------------------
                                        Financial Officer
                                        ---------------------------------------



<PAGE>   22


         The foregoing Stock Purchase Agreement is hereby executed as of the day
and year first above written.


                                           STATE OF WISCONSIN INVESTMENT BOARD

                                           By: /s/ John F. Nelson
                                               -------------------------------

                                           Name: John F. Nelson
                                                 -----------------------------

                                           Its: Investment Director
                                                ------------------------------



<PAGE>   23


         The foregoing Stock Purchase Agreement is hereby executed as of the day
and year first above written.


                                           CHARTER VENTURES II, L.P.

                                           By: /s/ A. Barr Dolan
                                               -------------------------------

                                           Name: A. Barr Dolan
                                                 -----------------------------

                                           Its: General Partner
                                                ------------------------------



<PAGE>   24


         The foregoing Stock Purchase Agreement is hereby executed as of the day
and year first above written.


                                          ZESIGER CAPITAL GROUP LLC, AS AGENT
                                          AND ATTORNEY-IN-FACT FOR THE
                                          PURCHASERS LISTED ON SCHEDULE A
                                          DESIGNATED WITH AN ASTERISK (*)

                                          By: /s/ Albert L. Zesiger
                                              -------------------------------

                                          Name: Albert L. Zesiger
                                                -----------------------------

                                          Its: Managing Director
                                               ------------------------------



<PAGE>   25


         The foregoing Stock Purchase Agreement is hereby executed as of the day
and year first above written.


                                        LOMBARD ODIER & CIE

                                        By: /s/ Alexandre Meyer, Carmela Gokok
                                            ----------------------------------

                                        Name: Alexandre Meyer, Carmela Gokok
                                              --------------------------------

                                        Its: Vice President, Vice President
                                             ---------------------------------



<PAGE>   26


         The foregoing Stock Purchase Agreement is hereby executed as of the day
and year first above written.


                                        DR. EDITH MARTIN

                                        By: /s/ Edith Martin
                                            ----------------------------------

                                        Name: Edith Martin
                                              --------------------------------


<PAGE>   27


                                   SCHEDULE A

                                   PURCHASERS


<TABLE>
<CAPTION>
Name and Address of Purchaser                Total Number of Shares     Aggregate Purchase Price
-----------------------------                ----------------------     ------------------------

<S>                                          <C>                        <C>
State of Wisconsin Investment Board            800,000                  $     997,600.00
121 East Wilson Street
Madison, WI 53702
Facsimile: (608) 266-2436

State of Wisconsin Investment Board            200,000                        249,400.00
121 East Wilson Street
Madison, WI 53702
Facsimile: (608) 266-2436

Charter Ventures II, L.P.                    1,000,000                      1,247,000.00
525 University Avenue
Suite 1500
Palo Alto, CA 94301
Facsimile: (650) 325-4762

Lombard Odier & Cie                          1,000,000                      1,247,000.00
11, Rue de la Corraterie
1204 Geneva
Switzerland
Facsimile: +41-22-709-38-31

Dr. Edith Martin                                36,000                         44,892.00
P.O. Box 11090
Jackson, WY 83002

Zesiger Capital Group LLC
320 Park Avenue
New York, NY 10022
Facsimile: (212) 508-6339/6329

         NFIB Corporate Account*                77,000                         96,019.00

         Norwalk Employees' Pension Plan*      108,000                        134,676.00
</TABLE>


<PAGE>   28


<TABLE>
<CAPTION>
Name and Address of Purchaser               Total Number of Shares     Aggregate Purchase Price
-----------------------------               ----------------------     ------------------------

<S>                                         <C>                        <C>
         Public Employee Retirement           385,000                  $     480,095.00
         System of Idaho*

         City of Stamford Firemen's            38,000                         47,386.00
         Pension Fund*

         Lazar Foundation*                     38,000                         47,386.00

         Roanoke College*                      38,000                         47,386.00

         HBL Charitable Unitrust*              38,000                         47,386.00

         Psychology Associates*                38,000                         47,386.00

         Peter Looram*                         38,000                         47,386.00

         Mary C. Anderson*                     77,000                         96,019.00

         Murray Capital, LLC*                  38,000                         47,386.00

         The Meehan Investment                 58,000                         72,326.00
         Partnership I, L.P.*

         Domenic J. Mizio*                     77,000                         96,019.00

         Theeuwes Family Trust,                77,000                         96,019.00
         Felix Theeuwes Trustee*

         Wells Family LLC*                    231,000                        288,057.00

         Albert L. Zesiger*                   115,000                        143,405.00

         Barrie Ramsay Zesiger*                58,000                         72,326.00

         John J. & Catherine H. Kayola*         8,000                          9,976.00

                  Zesiger Total             1,537,000                      1,916,639.00

Total                                       4,573,000                  $   5,702,531.00
</TABLE>


                                      -2-
<PAGE>   29


                                    EXHIBIT A

                [LETTERHEAD OF WILSON SONSINI GOODRICH & ROSATI]

February 6, 2001

To the Purchasers of
Common Stock of Heska Corporation
listed on Exhibit A attached hereto

Ladies and Gentlemen:

We have acted as counsel for Heska Corporation, a Delaware corporation (the
"Company"), in connection with the issuance and sale to you of 4,573,000 shares
of the Company's Common Stock (the "Shares") pursuant to the Heska Corporation
Stock Purchase Agreement dated as of February 1, 2001 between the Company and
each of the Purchasers listed on Exhibit A hereto (the "Agreement"). We are
rendering this opinion pursuant to Section 3(d)(iii) of the Agreement. Except as
otherwise defined herein, capitalized terms used but not defined herein have the
respective meanings given to them in the Agreement.

We have made such legal and factual examinations and inquiries as we have deemed
advisable or necessary for the purpose of rendering this opinion. In addition,
we have examined originals or copies of such corporate records of the Company,
certificates of public officials and such other documents which we consider
necessary or advisable for the purpose of rendering this opinion. In such
examination we have assumed the genuineness of all signatures on original
documents, the authenticity and completeness of all documents submitted to us as
originals, the conformity to original documents of all copies submitted to us
and the due execution and delivery of all documents where due execution and
delivery are a prerequisite to the effectiveness thereof.

As used in this opinion, the expression "to our knowledge," "known to us" or
similar language with reference to matters of fact means that, after an
examination of documents made available to us by the Company, and after
inquiries of officers of the Company, but without any further independent
factual investigation, we find no reason to believe that the opinions expressed
herein are factually incorrect. Further, the expression "to our knowledge",
"known to us" or similar language with reference to matters of fact refers to
the current actual knowledge of the attorneys of this firm who have worked on
matters for the Company. Except to the extent expressly set forth herein or as
we otherwise believe to be necessary to our opinion, we have not undertaken any
independent investigation to determine the existence or absence of any fact, and
no inference as to our knowledge of the existence or absence of any fact should
be drawn from our representation of the Company or the rendering of the opinion
set forth below.

For purposes of this opinion, we are assuming that you have all requisite power
and authority, and have taken any and all necessary corporate or partnership
action, to execute and deliver the Agreement, and we are assuming that the
representations and warranties made by the Purchasers in


<PAGE>   30


the Agreement and pursuant thereto are true and correct. We are also assuming
that the Purchasers have purchased the Shares for value, in good faith and
without notice of any adverse claims within the meaning of the Delaware General
Corporation Law. We are also assuming that the representations and warranties
made by the Company in the Agreement and pursuant thereto are true and correct
as to matters of fact.

         The opinions hereinafter expressed are subject to the following
qualifications:

                           (a) We express no opinion as to the effect of
applicable bankruptcy, insolvency, reorganization, moratorium or other similar
federal or state laws affecting the rights of creditors;

                           (b) We express no opinion as to the effect of rules
of law governing specific performance, injunctive relief or other equitable
remedies (regardless of whether any such remedy is considered in a proceeding at
law or in equity);

                           (c) We express no opinion as to compliance with the
anti-fraud provisions of applicable securities laws;

                           (d) We express no opinion as to the enforceability of
the indemnification provisions contained in the Agreement to the extent the
provisions thereof may be subject to limitations of public policy and the effect
of applicable statutes and judicial decisions;

                           (e) We are members of the Bar of the State of
California and, with respect to the securities laws of other states, we express
no opinion as to any matter relating to the laws of any jurisdiction other than
the federal laws of the United States of America, the laws of the State of
California and the Delaware General Corporation Law. To the extent this opinion
addresses applicable securities laws of states other than the State of
California or Delaware, we have not retained nor relied on the opinion of
counsel admitted to the bar of such states, but rather have relied on
compilations of the securities laws of such states contained in reporting
services presently available to us.

On the basis of the foregoing, in reliance thereon and with the foregoing
qualifications, we are of the opinion that:

1. The Company has been duly incorporated and is validly existing in good
standing under the laws of the State of Delaware. The Company is qualified to do
business as a foreign corporation and is in good standing in the State of
Colorado. The Company has the requisite corporate power to own or lease its
property and assets and to conduct its business as currently conducted.

2. The Company has all requisite legal and corporate power to execute and
deliver the Agreement, to sell and issue the Shares thereunder, and to carry out
and perform its obligations under the terms of the Agreement. The Agreement has
been duly authorized, executed and delivered by the Company.


                                      -2-
<PAGE>   31


3. The Shares have been duly authorized and when issued, delivered and paid for
in accordance with the terms of the Agreement, will be validly issued, fully
paid and nonassessable and free of any pre-emptive or similar rights.

4. To our knowledge and except as disclosed in filings with the Securities and
Exchange Commission, there are no actions, suits, proceedings or investigations
pending against the Company or its properties before any court or governmental
agency (nor, to our knowledge, has the Company received any actual threat
thereof), which, either in any case or in the aggregate, are likely to result in
any material adverse change in the business or financial condition of the
Company or any of its properties, or in any material impairment of the right or
ability of the Company to carry on its business as now conducted, or which
questions the validity of the Agreement or any action taken or to be taken by
the Company in connection therewith.

5. Subject to the accuracy of the Purchasers' representations in Section 5 of
the Agreement and their responses (if any) to the Company's inquiries, we are of
the opinion that the offer and sale of the Shares by the Company to the
Purchasers is exempt from the registration requirements of the Securities Act of
1933, as amended, subject to timely filing of a Form D pursuant to Securities
and Exchange Commission Regulation D.

6. The execution and delivery of the Agreement by the Company and the
consummation of the sale of the Shares by the Company as contemplated therein do
not violate any provisions of the Company's Certificate of Incorporation or
By-laws; or any provision of any applicable federal or state law, rule or
regulation; or any material agreements to which the Company is a party.

7. All consents, approvals, authorizations, or orders of, and filings,
registrations and qualifications with any regulatory authority or governmental
body in the United States required for the issuance by the Company of the Shares
as contemplated by the Agreements, have been made or obtained, except for (i)
the filing of a Form D pursuant to Securities and Exchange Commission Regulation
D and (ii) filings required to be made by the Purchasers under the
Hart-Scott-Rodino Antitrust Improvement Act of 1976.

8. This opinion is intended solely for your benefit and is not to be made
available to or be relied upon by any other person, firm, or entity without our
prior written consent.

                                            Very truly yours,


                                            WILSON, SONSINI, GOODRICH & ROSATI
                                            Professional Corporation


                                      -3-
<PAGE>   32


                                    EXHIBIT B

                             SCHEDULE OF EXCEPTIONS



                                      None.

<PAGE>   33



                                   APPENDIX I

                                HESKA CORPORATION

                         STOCK CERTIFICATE QUESTIONNAIRE


         Pursuant to Section 3 of the Agreement, please provide us with the
         following information:

1.       The exact name that your Shares are to be registered in (this is the
         name that will appear on your stock certificate(s)). You may use a
         nominee name if appropriate:

         ----------------------------------

2.       The relationship between the Purchaser of the Shares and the Registered
         Holder listed in response to item 1 above:
                                                   -----------------------------

3.       The mailing address of the Registered Holder listed in response to item
         1 above:

         -----------------------------------

         -----------------------------------

         -----------------------------------

         -----------------------------------

4.       The Social Security Number or Tax Identification Number of the
         Registered Holder listed in response to item 1 above:

         -----------------------------------



<PAGE>   34


                                   APPENDIX II

                                HESKA CORPORATION

                      REGISTRATION STATEMENT QUESTIONNAIRE


         In connection with the preparation of the Registration Statement,
please provide us with the following information:

1.       Pursuant to the "Selling Stockholder" section of the Registration
         Statement, please state your or your organization's name exactly as it
         should appear in the Registration Statement:

         -------------------------------------------------------

2.       Please provide the number of shares that you or your organization will
         own immediately after Closing, including those Shares purchased by you
         or your organization pursuant to this Purchase Agreement and those
         shares purchased by you or your organization through other
         transactions:
                       ---------------------------------------------

3.       Have you or your organization had any position, office or other
         material relationship within the past three years with the Company or
         its affiliates?

                  _____ Yes         _____ No



         If yes, please indicate the nature of any such relationships below:

         -------------------------------------------------------
         -------------------------------------------------------
         -------------------------------------------------------
         -------------------------------------------------------
<PAGE>   35


                                  APPENDIX III

                   PURCHASER'S CERTIFICATE OF SUBSEQUENT SALE


         The undersigned, an officer of, or other person duly authorized by



--------------------------------------------------------------------------------
              [fill in official name of individual or institution]

hereby certifies that he/she/it is the Purchaser of the shares evidenced by the
attached certificate, and as such, sold such shares on ________________, 200__
in accordance with Registration Statement number 333-________________, and
complied with the requirement of delivering a current prospectus in connection
with such sale.

PRINT OR TYPE:

Name of Purchaser (Individual or Institution):


--------------------------------------------------------------------------------


Name of Individual representing Purchaser (if an Institution)


--------------------------------------------------------------------------------


Title of Individual representing Purchaser (if an Institution):


--------------------------------------------------------------------------------


SIGNATURE:

Individual Purchaser or Individual representing Purchaser:


--------------------------------------------------------------------------------