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                                                                    EXHIBIT 10.1

                     AMENDMENT TO STOCK PURCHASE AGREEMENT


        This Amendment to Stock Purchase Agreement (this "Amendment") is made as
of the 18th day of April, 2001 between ChromaVision Medical Systems, Inc., a
Delaware corporation (the "Company"), and VennWorks LLC, a Delaware limited
liability company formerly named incuVest LLC, (the "Purchaser").

RECITALS

        The Company and the Purchaser are parties to a Stock Purchase Agreement
made as of January 31, 2001 (the "Stock Purchase Agreement") providing for the
purchase by the Purchaser from the Company of $5,000,000 in aggregate purchase
price of shares of Common Stock of the Company on the terms and at the dates set
forth in the Stock Purchase Agreement. The parties now desire to amend the Stock
Purchase Agreement on the terms set forth in this Amendment.

AMENDMENT

        The parties hereby agree that the Stock Purchase Agreement shall be
amended as follows:

        1. Section 3 of the Stock Purchase Agreement is amended to read in full
as follows:

                "The Company has requested, pursuant to the Stock Purchase
        Agreement, that the Purchaser purchase the first $2,000,000 of aggregate
        purchase price of shares of the Company's Common Stock. Such purchases
        shall be made (without further request or notice from the Company) of
        the numbers of shares which have the aggregate purchase prices set forth
        below on the dates set forth below:

                        (a)     $100,000 on each of April 23 and April 27, 2001;

                        (b)     $200,000 on each of May 4, May 11, May 18 and
                                May 25, 2001; and

                        (c)     $250,000 on each of June 1, June 8, June 15 and
                                June 22, 2001.

                The number of shares to be purchased in each of the weekly
        purchases referred to above shall be determined by dividing the
        aggregate purchase price for that particular purchase set forth above by
        the greater of (i) $7 plus interest thereon at the rate of 8% per annum
        from April 20, 2001 until the date the shares are purchased or (ii) the
        average of the closing prices per share of Common Stock on the Nasdaq
        National Market for each of the twenty trading days ending three
        business days before the date of each such purchase but in no event more
        than $14 per share. For purposes of (i) above, the increase in the $7
        per share price resulting from the interest shall be rounded to the
        nearest one-hundredth of one cent, and in the event the foregoing
        results in a fractional share for the aggregate purchase on any day, the
        fraction shall be rounded down and the purchase price of the fractional
        share shall not be paid. In the event the shares of Company



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        Common Stock are no longer quoted on the Nasdaq National Market, the
        purchase price shall be determined in like manner by reference to the
        principal market where the shares are then quoted for each day in the
        twenty day trading period. If the shares do not trade on any of the
        twenty trading days referred to above, that day shall be ignored in
        calculating the average. Each date set forth in (a) through (c) above
        shall be deemed to be a Closing Day for purposes of the Stock Purchase
        Agreement, as amended by this Amendment.

                In addition, the Company will have the right to request that the
        Purchaser purchase shares having up to the maximum aggregate price set
        forth below during the periods set forth below:

                        (A) $4,000,000 on a Closing Date between July 1, 2001
                and September 28, 2001 less the aggregate purchase price of the
                shares, if any, purchased pursuant to (a) through (c) above; and

                        (B) $5,000,000 on a Closing Date between October 1, 2001
                and December 28, 2001 less the aggregate purchase price of the
                shares, if any, purchased pursuant to (a) through (c) and (A)
                above."

        Section 4 of the Stock Purchase Agreement shall apply only to purchases
pursuant to (A) and (B) above. The failure of the Company to exercise its option
to request the purchase of any of the shares referred to in (A) or (B) above
shall not affect its right to request the purchase of shares during any later
period, except that in no event will the Company have the right to request the
purchase of shares on a Closing Date after December 28, 2001. The purchase price
of shares purchased pursuant to (A) and (B) shall be the amount set forth in
Section 2 of the Agreement.

        2. Acceleration for Default. In the event of an Event of Default the
Company will have the right at any time thereafter to request that Purchaser
purchase the entire amount of shares referred to in Section 1 of this Amendment
(including the shares referred to in (a) through (c) as well as (A) and (B) of
said Section 1) to the extent they have not been previously purchased. The
Closing Date for any such purchase shall be three business days after the giving
of written notice by the Company to the Purchaser of its election to exercise
its rights under this Section 2. "Event of Default" means any of the following:
(i) any default in the performance of any obligation under this Agreement which
is not cured within fifteen (15) days after delivery of written notice of the
default by the Company to Purchaser and (ii) any inaccuracy in any
representation or warranty made by Purchaser pursuant to Section 4(a) through
(c) of this Amendment or pursuant to the Stock Purchase Agreement.

        3. Closing of Purchases. Section 5 of the Stock Purchase Agreement is
hereby amended to read in full as follows:

                "The closing of each purchase and sale of shares shall be held
        on the Closing Date for the purchase specified in Section 3 (as amended
        by Section 1 of this Amendment). Each closing will be accomplished by
        the delivery of immediately available funds in the amount of the
        purchase price to be paid by wire transfer to the account of the
        Company. Promptly upon being notified by its



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        bank of receipt of the funds by wire transfer, the Company will cause a
        certificate for the shares purchased to be delivered to the Purchaser by
        hand delivery or by recognized overnight courier at 530 Madison Avenue,
        New York, N.Y 10017. The wire transfer shall be sent in accordance with
        the following instructions or such other instructions as the Company may
        provide to the Purchaser in writing at least two business days prior to
        the date any such wire transfer is to be sent:

                               Bank of America
                               ABA #121000358
                               Account #14178-03031
                               Account Name:  ChromaVision Medical Systems, Inc"

        4. Representations and Warranties of the Purchaser. The Purchaser hereby
represents and warrants to the Company as follows:

                (a) As of April 6, 2001 and as of the date of this Agreement the
        Purchaser does not have in its possession or subject to its control the
        $2,000,000 in cash or cash equivalents (as defined in accordance with
        generally accepted accounting principles) required to meet its
        obligations under Section 3(a) of the Stock Purchase Agreement as in
        effect prior to this Amendment. Purchaser represents and warrants to the
        Company that approximately $4 million in cash reflected on its balance
        sheet is subject to the terms of an agreement or agreements with HSBC
        that prohibit its use to purchase the Company's Common Stock.

                (b) Each of the financial statements delivered by the Purchaser
        shall have been prepared in accordance with generally accepted
        accounting principles consistently applied except that the footnote
        disclosure required by generally accepted accounting principles shall
        not be required.

                (c) All of the representations and warranties set forth in the
        Stock Purchase Agreement are true and correct as of the date of this
        Amendment.

        5. Representations and Warranties of the Company. The Company represents
and warrants that all of its representations and warranties set forth in the
Stock Purchase Agreement are true and correct as of the date of this Amendment.

        6. Obligation to Provide Financial Statements. Concurrently with the
execution and delivery of this Amendment, the Purchaser is providing to the
Company its most recent available financial statements consisting of an income
statement, balance sheet and statement of cash flows, which shall be as of a
date not earlier than February 28, 2001 and for the monthly period then ended
and the calendar year to date. The Company agrees to keep the financial
statements confidential and not to make them available or disclose the contents
thereof to any person or entity except to its Chief Executive Officer, Chief
Financial Officer and outside legal counsel, except as required by law and
except that the Company can provide a verbal summary of the contents of the
financial statements to its Board of Directors.



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        7. Unconditional Nature of Purchaser's Obligation. Purchaser
acknowledges that this Amendment is being entered into because Purchaser is
unable to meet its obligations to purchase $2;,000,000 in aggregate purchase
price of shares of Company Common Stock in accordance with the terms of the
Stock Purchase Agreement. Purchaser agrees that its obligation to purchase the
shares pursuant to this Amendment is unconditional and will not be affected by
any change in the business, financial condition, results of operations or
prospects of the Company, whether occurring before or after this Agreement.
Purchaser further acknowledges that the Company has made no representation or
warranty, express or implied, to the Purchaser except as specifically set forth
in this Agreement and has provided to the Purchaser all information and
documents and answered all questions asked by the Purchaser in order for the
Purchaser to evaluate this Amendment and the Stock Purchase Agreement and the
risks to it of the transactions contemplated hereby and thereby.

        8. Continued Effect of Stock Purchase Agreement. Except as amended
hereby, the Stock Purchase Agreement shall remain in full force and effect.

        9. Counterparts. This Amendment 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 of the parties hereto and
delivered to the other party by telephone facsimile, personal delivery, delivery
by overnight courier of recognized standing or by first class U.S. mail.

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

CHROMAVISION MEDICAL SYSTEMS, INC.          VENNWORKS LLC

By:                                         By:
   -------------------------------             ---------------------------------
Name:                                       Name:
     -----------------------------               -------------------------------
Title:                                      Title:
      ----------------------------                ------------------------------



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