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                                                                    EXHIBIT 99.1
 
 
                                     LOGO
                           LAM RESEARCH CORPORATION
                             4650 CUSHING PARKWAY
                           FREMONT, CALIFORNIA 94538
                                                                   July 7, 1997
 
Dear Stockholder:
 
  You are cordially invited to attend a special meeting ("Lam Special
Meeting") of the stockholders of Lam Research Corporation ("Lam") to be held
at the offices of Lam, 4650 Cushing Parkway, Fremont, California, on August 5,
1997, at 2:00 p.m., local time. At the Lam Special Meeting, you will be asked
to consider and vote on, (i) a proposal (the "Share Issuance") to approve the
issuance of shares of common stock of Lam, par value $0.001 per share ("Lam
Common Stock") pursuant to an Agreement and Plan of Merger dated as of March
24, 1997 (the "Merger Agreement"), pursuant to which OnTrak Systems, Inc.
("OnTrak") will be acquired by Lam by means of a merger (the "Merger") of
Omega Acquisition Corporation, a wholly-owned subsidiary of Lam, with and into
OnTrak, resulting in OnTrak becoming a wholly-owned subsidiary of Lam; (ii) a
proposal to approve and adopt the Lam Research Corporation 1997 Stock
Incentive Plan (the "Lam 1997 Stock Plan"); (iii) a proposal to amend the
Certificate of Incorporation of Lam (the "Certificate") to eliminate
stockholder action by written consent (the "Written Consent Amendment"); and
(iv) a proposal to amend the Certificate to eliminate cumulative voting in the
election of members of the Board of Directors (the "Cumulative Voting
Amendment" and together with the Written Consent Amendment, the "Certificate
of Incorporation Amendments").
 
  The Merger Agreement provides for the conversion and exchange of each
outstanding share of common stock of OnTrak, par value $0.0001 per share
("OnTrak Common Stock"), into 0.83 of a share of Lam Common Stock subject to
the following adjustment (the "Exchange Ratio"). If the average of the daily
closing sale prices per share of the Lam Common Stock as reported on the
Nasdaq National Market on the ten trading days ending the eighth trading day
preceding the special meeting of stockholders of OnTrak (the "Lam Closing
Value") falls below certain thresholds specified in the Merger Agreement, then
Lam may elect to adjust the Exchange Ratio to that number of shares of Lam
Common Stock equal to $24.90 divided by the Lam Closing Value. If Lam
determines not to adjust the Exchange Ratio in those circumstances, then
OnTrak has the option to terminate the Merger Agreement. If adjusted, the
Exchange Ratio will be fixed prior to the Lam Special Meeting and the special
meeting of stockholders of OnTrak. Stockholders may ascertain whether Lam has
adjusted the Exchange Ratio or whether OnTrak has terminated the Merger
Agreement by phoning 1-888 LAM-TRAK or logging onto the World Wide Web at
http://www.lamrc.com at any time after July 25, 1997. If, subsequent to the
mailing of the Proxy Card, you wish to revoke or change your vote, you may do
so by phoning 1-888-LAM-TRAK or logging onto the World Wide Web at
http://www.lamrc.com at any time after July 25, 1997, and following the
instructions provided by the messages thereon.
 
  Following the Merger, based on the number of shares of Lam Common Stock and
OnTrak Common Stock outstanding as of March 31, 1997, and an Exchange Ratio of
0.83 of a share of Lam Common Stock for each share of OnTrak Common Stock, the
former stockholders of OnTrak will hold approximately 6,422,165 shares, or
17.3% of Lam Common Stock. In addition, each outstanding option or right to
purchase OnTrak Common Stock under OnTrak's stock option and stock purchase
plans will be assumed by Lam and will be converted into an option or right to
purchase Lam Common Stock, with appropriate adjustments, based upon the
Exchange Ratio, made to the number of shares issuable under the option and to
the exercise or purchase price per share of each option or right. On June 25,
1997, the last practicable date prior to printing of the Joint Proxy
Statement/Prospectus, the last sale prices of Lam Common Stock and OnTrak
Common Stock as reported on the Nasdaq National Market, were $35.75 and
$28.75, respectively.
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  Pursuant to the Merger Agreement, an Office of the Chairman will be created
at Lam and will include James W. Bagley, currently the Chairman and Chief
Executive Officer at OnTrak, and me. I will be the Chairman of the Board, and
as contemplated by the Merger Agreement, Lam will enter into an employment
agreement with Mr. Bagley pursuant to which he will serve as Chief Executive
Officer of Lam. In addition, the Lam Board of Directors will be expanded and
Mr. Bagley and Richard J. Elkus, Jr., currently directors of OnTrak, will be
appointed to the Board of Directors of Lam.
 
  In the material accompanying this letter, you will find a Notice of Special
Meeting of Stockholders, a Joint Proxy Statement/Prospectus and a Proxy Card.
In addition to describing the terms and conditions of the Merger Agreement,
the enclosed Joint Proxy Statement/Prospectus sets forth information,
including summary financial data, about Lam and OnTrak. The complete text of
the Merger Agreement appears as Annex A to the Joint Proxy
Statement/Prospectus. Please carefully review all of these materials and
consider the information contained in them. Your vote on the Share Issuance is
important.
 
  Approval of each of the Share Issuance and the Lam 1997 Stock Plan requires
the affirmative vote of the majority of the total votes cast in person or by
proxy at the Lam Special Meeting. Approval of each of the Written Consent
Amendment and the Cumulative Voting Amendment requires the affirmative vote of
the holders of a majority of the outstanding shares of Lam Common Stock.
 
  AFTER CAREFUL CONSIDERATION, YOUR BOARD OF DIRECTORS HAS UNANIMOUSLY
APPROVED THE MERGER AND THE TRANSACTIONS CONTEMPLATED THEREBY, INCLUDING THE
SHARE ISSUANCE AND THE LAM 1997 STOCK PLAN, AND THE CERTIFICATE OF
INCORPORATION AMENDMENTS, AND HAS CONCLUDED THAT APPROVAL AND ADOPTION OF
THESE PROPOSALS ARE IN THE BEST INTERESTS OF LAM AND ITS STOCKHOLDERS. YOUR
BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT STOCKHOLDERS VOTE FOR APPROVAL
OF THE SHARE ISSUANCE, FOR APPROVAL AND ADOPTION OF THE LAM 1997 STOCK PLAN
AND FOR APPROVAL OF THE CERTIFICATE OF INCORPORATION AMENDMENTS.
 
  Stockholders are urged to review carefully the information contained in the
accompanying Notice of Special Meeting and Joint Proxy Statement/Prospectus,
including in particular the information under the captions "Risk Factors,"
"Lam Special Meeting--Recommendations of Lam Board of Directors," "The Merger
and Related Transactions--Joint Reasons For the Merger," "--Lam's Reasons For
the Merger" and "--Material Contacts and Board Deliberations" prior to making
any voting decision in connection with their Lam Common Stock.
 
  Regardless of the size of your holdings, it is important that your shares be
voted at the Lam Special Meeting. All stockholders are invited to attend the
Lam Special Meeting in person. Whether or not you plan to attend the Lam
Special Meeting in person, please complete, sign and promptly return the
enclosed Proxy Card in the enclosed postage-prepaid envelope to assure
representation of your shares. You may revoke your proxy at any time before it
has been voted, and if you attend the Lam Special Meeting you may vote in
person even if you have previously returned your Proxy Card. Your prompt
cooperation will be greatly appreciated.
 
                                          Sincerely,
 
                                          /s/Roger D. Emerick
                                          Roger D. Emerick
                                          Chairman of the Board and Chief
                                           Executive Officer
 
                YOUR PROXY IS IMPORTANT--PLEASE VOTE PROMPTLY.
