EXHIBIT 99.(a)(1)(E)

                          OFFER TO PURCHASE FOR CASH
                    All Outstanding Shares of Common Stock
                       (Including the Associated Rights)
                                      of
                       ProVantage Health Services, Inc.
                                      at
                             $12.25 Net Per Share
                                      by
                             PV Acquisition Corp.

                    an indirect wholly owned subsidiary of
                               Merck & Co., Inc.

        THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
       NEW YORK CITY TIME, ON WEDNESDAY, JUNE 14, 2000, UNLESS EXTENDED.


                                                                   May 10, 2000

To Our Clients:

   Enclosed for your consideration are the Offer to Purchase, dated May 10,
2000 (the "Offer to Purchase"), and the related Letter of Transmittal (which
together constitute the "Offer"), relating to the offer by PV Acquisition
Corp., a Delaware corporation ("Offeror") and wholly owned indirect subsidiary
of Merck & Co., Inc., a New Jersey corporation ("Parent"), to purchase all of
the outstanding shares of Common Stock, $0.01 par value per share, of
ProVantage Health Services, Inc., a Delaware corporation (the "Company"),
including the associated preferred share purchase rights issued pursuant to
the Rights Agreement, dated as of March 12, 1999, and amended as of May 4,
2000, by and between the Company and Norwest Bank Minnesota, N.A., as Rights
Agent (the "Rights," and the shares of Common Stock inclusive of their
respective Rights, the "Shares"), at a price of $12.25 per Share, net to the
seller in cash, without interest thereon, upon the terms and subject to the
conditions set forth in the Offer. The Offer is being made in connection with
the Agreement and Plan of Merger, dated as of May 4, 2000, among Parent,
Offeror and the Company (the "Merger Agreement"). Offeror is a corporation,
newly formed by Parent in connection with the Offer and the transactions
contemplated thereby. This material is being forwarded to you as the
beneficial owner of Shares carried by us in your account but not registered in
your name.

   We are (or our nominee is) the holder of record of Shares held by us for
your account. A tender of such Shares can be made only by us as the holder of
record and pursuant to your instructions. The Letter of Transmittal is
furnished to you for your information only and cannot be used to tender Shares
held by us for your account.

   Accordingly, we request instructions as to whether you wish us to tender on
any or all of the Shares held by us for your account, pursuant to the terms
and conditions set forth in the Offer.

   Please note the following:

     1. The tender price is $12.25 per Share, net to the seller in cash,
  without interest.

     2. The Offer is conditioned upon, among other things, (i) there being
  validly tendered and not withdrawn immediately prior to the expiration of
  the Offer that minimum number of shares which would represent at least a
  majority of the Shares entitled to vote that are outstanding on a fully
  diluted basis after giving effect to the exercise or conversion of all
  options, rights and securities exercisable or convertible into or
  exchangeable for Shares or such voting securities and (ii) the waiting
  period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
  amended, and the regulations thereunder having expired or been terminated
  prior to the expiration of the Offer. The Offer is also subject to the
  satisfaction of certain other conditions. See Section 15 of the Offer to
  Purchase.


     3. The Offer is being made for all of the outstanding Shares.

     4. Tendering stockholders will not be obligated to pay brokerage fees or
  commissions or, except as otherwise provided in Instruction 6 of the Letter
  of Transmittal, transfer taxes on the purchase of Shares by Offeror
  pursuant to the Offer. However, federal income tax backup withholding may
  be required, unless an exemption is provided or unless the required
  taxpayer identification information is provided. See of Important Tax
  Information of the Letter of Transmittal.

     5. The Board of Directors of the Company has unanimously (by all those
  directors present) approved the Offer, the Merger (as defined in the Offer
  to Purchase) and the Merger Agreement, has determined that the terms of the
  Offer and the Merger are fair to, and in the best interests of, the
  stockholders of the Company, and has recommended that the stockholders of
  the Company accept the Offer and approve the Merger and the Merger
  Agreement.

     6. In all cases, payment for Shares tendered and accepted for payment
  pursuant to the Offer will be made only after timely receipt by the
  Depositary of (i) certificates for such Shares or timely confirmation of a
  book-entry transfer of such Shares into the Depositary's account at The
  Depository Trust Company, pursuant to the procedures set forth in Section 3
  of the Offer to Purchase, (ii) a properly completed and duly executed
  Letter of Transmittal (or a manually signed facsimile thereof) with all
  required signature guarantees or, in the case of a book-entry transfer, an
  Agent's Message (as defined in Section 2 of the Offer to Purchase) and
  (iii) any other documents required by the Letter of Transmittal.

   If you wish to have us tender any or all of the Shares held by us for your
account, please so instruct us by completing, executing, detaching and
returning to us the instruction form set forth below. If you authorize the
tender of your Shares, all such Shares will be tendered unless otherwise
specified below. Please forward your instructions to us to allow us ample time
to tender your Shares on your behalf prior to the expiration of the Offer.

   The Offer is not being made to, nor will tenders be accepted from or on
behalf of, holders of Shares residing in any jurisdiction in which the making
of the offer or the acceptance thereof would not be in compliance with the
securities, blue sky or other laws of such jurisdiction. However, Offeror may,
in its discretion, take such action as it may deem necessary to make the Offer
in any jurisdiction and extend the Offer to holders of Shares in such
jurisdiction.

   In any jurisdiction where the securities, blue sky or other laws require
the Offer to be made by a licensed broker or dealer, the Offer will be deemed
to be made on behalf of Offeror by J.P. Morgan Securities Inc., the Dealer
Manager for the Offer, or one or more registered brokers or dealers that are
licensed under the laws of such jurisdiction.

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                         INSTRUCTIONS WITH RESPECT TO
                        THE OFFER TO PURCHASE FOR CASH
                    ALL OUTSTANDING SHARES OF COMMON STOCK
                       (INCLUDING THE ASSOCIATED RIGHTS)
                                      OF
                       PROVANTAGE HEALTH SERVICES, INC.
                                      BY
                             PV ACQUISITION CORP.

   The undersigned acknowledge(s) receipt of your letter, the enclosed Offer
to Purchase dated May 10, 2000, and the related Letter of Transmittal (which
together constitute the "Offer") in connection with the offer by PV
Acquisition Corp., a Delaware corporation and indirect wholly owned subsidiary
of Merck & Co., Inc., a New Jersey corporation, to purchase all outstanding
shares of Common Stock, $0.01 par value per share, of ProVantage Health
Services, Inc., a Delaware corporation (the "Company"), including the
associated preferred share purchase rights issued pursuant to the Rights
Agreement, dated as of March 12, 1999, and amended as of May 4, 2000, by and
between the Company and Norwest Bank Minnesota, N.A., as Rights Agent (the
"Rights," and the shares of Common Stock inclusive of their respective Rights,
the "Shares"), at a purchase price of $12.25 per Share, net to the seller in
cash, without interest, upon the terms and subject to the conditions set forth
in the Offer.

   This will instruct you to tender to Offeror the number of Shares indicated
below (or if no number is indicated below, all Shares) which are held by you
for the account of the undersigned, upon the terms and subject to the
conditions set forth in the Offer.

 Number of Shares to be
  Tendered:*


                                                       SIGN HERE

Account Number: _____________________    _____________________________________

Date: ____________________________ ,     _____________________________________
                                                      Signature(s)

                                         _____________________________________

                                         _____________________________________
                                                    (Print Name(s))

                                         _____________________________________

                                         _____________________________________
                                                  (Print Addresss(es))

                                         _____________________________________
                                                (Area Code and Telephone
                                                     Number(s))

                                         _____________________________________
                                              (Taxpayer Identification or
                                             Social Security Number(s))

- --------
* Unless otherwise indicated, it will be assumed that all Shares held by us
  for your account are to be tendered.


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