Exhibit (a)(31)

January 21, 2008

Board of Directors

Ventana Medical Systems, Inc.

1910 Innovation Park Drive

Tucson, Arizona 85755

Members of the Board of Directors:

Ventana Medical Systems, Inc. (the “Company”), Roche Holdings, Inc. (the “Acquiror”) and Rocket Acquisition Corporation, a newly formed, wholly owned subsidiary of the Acquiror (the “Acquisition Sub”), are entering into an Agreement and Plan of Merger, dated as of January 21, 2008 (the “Agreement”), pursuant to which (i) the Acquiror and the Acquisition Sub would amend the tender offer (the “Tender Offer”) for all outstanding shares of the common stock, par value $0.001 per share, of the Company (the “Company Shares”) to increase the purchase price to $89.50 per share, net to the seller in cash (the “Consideration”), and (ii) Acquisition Sub would be merged with the Company in a merger (the “Merger”), in which each Company Share not acquired in the Tender Offer, other than Company Shares held in treasury or held by the Acquiror or its subsidiaries, or as to which dissenter’s rights have been perfected, would be converted into the right to receive the Consideration. The Tender Offer and the Merger, taken together, are referred to as the “Transaction”.

You have asked us whether, in our opinion, the Consideration to be received by the holders of the Company Shares pursuant to the Transaction is fair from a financial point of view to such holders, other than the Acquiror, the Acquisition Sub and their respective affiliates.

In arriving at the opinion set forth below, we have, among other things:

(1)	Reviewed certain publicly available business and financial information relating to the Company that we deemed to be relevant;
(2)	Reviewed certain information, including financial forecasts, relating to the business, earnings, cash flow, assets, liabilities and prospects of the Company furnished to us by the Company;
(3)	Conducted discussions with members of senior management of the Company concerning the matters described in clauses 1 and 2 above;
(4)	Reviewed the market prices and valuation multiples for the Company Shares and compared them with those of certain other publicly traded companies that we deemed to be relevant;
(5)	Reviewed the results of operations of the Company and compared them with those of certain other publicly traded companies that we deemed to be relevant;
(6)	Compared the proposed financial terms of the Transaction with the financial terms of certain other transactions that we deemed to be relevant;

Board of Directors
Ventana Medical Systems, Inc.
January 21, 2008
Page 2

(7)	Participated in certain discussions and negotiations among representatives of the Company and the Acquiror and their financial and legal advisors;
(8)	Reviewed the Agreement; and
(9)	Reviewed such other financial studies and analyses and took into account such other matters as we deemed necessary, including our assessment of general economic, market and monetary conditions.

In preparing our opinion, we have assumed and relied on the accuracy and completeness of all information supplied or otherwise made available to us, discussed with or reviewed by or for us, or publicly available, and we have not assumed any responsibility for independently verifying such information or undertaken an independent evaluation or appraisal of any of the assets or liabilities of the Company or been furnished with any such evaluation or appraisal, nor have we evaluated the solvency or fair value of the Company under any state or federal laws relating to bankruptcy, insolvency or similar matters. In addition, we have not assumed any obligation to conduct any physical inspection of the properties or facilities of the Company. With respect to the financial forecast information furnished to or discussed with us by the Company, we have assumed that they have been reasonably prepared and reflect the best currently available estimates and judgment of the Company’s management as to the expected future financial performance of the Company.

Our opinion is necessarily based upon market, economic and other conditions as they exist and can be evaluated on, and on the information made available to us as of, the date hereof.

We are acting as financial advisor to the Company in connection with the Transaction and will receive a fee from the Company for our services, a significant portion of which is contingent upon the consummation of the Transaction. In addition, the Company has agreed to indemnify us for certain liabilities arising out of our engagement.

We have, in the past, provided financial advisory and financing services to the Acquiror and its affiliates unrelated to the Transaction and have received fees for the rendering of such services. In addition, in the ordinary course of our business, we or our affiliates may actively trade the Company Shares and other securities of the Company, as well as securities of the Acquiror, for our own account and for the accounts of customers and, accordingly, may at any time hold a long or short position in such securities.

This opinion is for the use and benefit of the Board of Directors of the Company. Our opinion does not address the merits of the underlying decision by the Company to engage in the Transaction and does not constitute a recommendation to any shareholder as to whether such shareholder should tender any Company Shares pursuant to the Tender Offer and how such shareholder should vote on the proposed Merger or any matter related thereto. In addition, you have not asked us to address, and this opinion does not address, the fairness to, or any other consideration of, the holders of any class of securities, creditors or other constituencies of the Company, other than the holders of the Company Shares. In rendering this opinion, we express no view or opinion with respect to the fairness (financial or otherwise) of the amount or nature or any other aspect of any compensation payable to or to be received by any officers, directors, or employees of any parties to the Transaction, or any class of such persons, relative to the Consideration. Our opinion has been authorized for issuance by the U.S. Fairness Opinion (and Valuation Letter) Committee of Merrill Lynch.

Board of Directors
Ventana Medical Systems, Inc.
January 21, 2008
Page 3

On the basis of and subject to the foregoing, we are of the opinion that, as of the date hereof, the Consideration to be received by the holders of the Company Shares pursuant to the Transaction is fair from a financial point of view to the holders of such shares, other than the Acquiror, the Acquisition Sub and their respective affiliates.

Very truly yours,

MERRILL LYNCH, PIERCE, FENNER & SMITH

INCORPORATED