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                   PRELIMINARY COPY -- SUBJECT TO COMPLETION
 
                             [RED LION LETTERHEAD]
 
                                                                October   , 1996
 
To the Stockholders of Red Lion Hotels, Inc.:
 
     You are cordially invited to attend a Special Meeting of Stockholders (the
"Special Meeting") of Red Lion Hotels, Inc. ("Red Lion") to be held on
day, November   , 1996, at 9:00 a.m. (local time), at             .
 
     At the Special Meeting, you will be asked to consider and vote upon a
proposal to approve and adopt an Agreement and Plan of Merger dated as of
September 12, 1996 (the "Merger Agreement"), by and among Red Lion, Doubletree
Corporation ("Doubletree") and RLH Acquisition Corp., a wholly owned subsidiary
of Doubletree ("Merger Sub"), and the merger of Merger Sub with and into Red
Lion (the "Merger"). Under the terms of the Merger Agreement, each share of
Common Stock, par value $.01 per share, of Red Lion ("Red Lion Common Stock")
which is outstanding immediately prior to the Merger will be converted into the
right to receive (i) $21.30 in cash and (ii) 0.2398 shares of common stock, par
value $.01 per share, of Doubletree (such cash and stock consideration,
together, the "Merger Consideration"), subject to adjustment under certain
circumstances as described in the accompanying Proxy Statement/Prospectus.
Detailed information concerning the proposed Merger are set forth in the
accompanying Notice of the Special Meeting and Proxy Statement/Prospectus, which
you are urged to read carefully.
 
     AFTER CAREFUL CONSIDERATION, THE BOARD OF DIRECTORS OF RED LION HAS
UNANIMOUSLY DETERMINED THAT THE TERMS OF THE PROPOSED MERGER ARE FAIR TO, AND IN
THE BEST INTERESTS OF, RED LION AND ITS STOCKHOLDERS. YOUR BOARD OF DIRECTORS
HAS CAREFULLY REVIEWED AND CONSIDERED THE TERMS AND CONDITIONS OF THE MERGER
AGREEMENT AND THE OPINION OF SMITH BARNEY INC., RED LION'S FINANCIAL ADVISOR,
STATING THAT, AS OF THE DATE OF SUCH OPINION, THE MERGER CONSIDERATION TO BE
RECEIVED BY THE HOLDERS OF RED LION COMMON STOCK WAS FAIR FROM A FINANCIAL POINT
OF VIEW TO SUCH HOLDERS. ACCORDINGLY, THE BOARD HAS UNANIMOUSLY APPROVED THE
MERGER AGREEMENT AND THE MERGER, AND UNANIMOUSLY RECOMMENDS THAT ALL
STOCKHOLDERS VOTE FOR APPROVAL AND ADOPTION OF THE MERGER AGREEMENT AND THE
MERGER.
 
     The affirmative vote of the holders of not less than a majority of the
outstanding shares of Red Lion Common Stock will be necessary for approval and
adoption of the Merger Agreement and the Merger. As of October   , 1996, Red
Lion, a California Limited Partnership (the "Partnership") beneficially owned
20,900,000 shares (or approximately 66.7% of the then outstanding shares) of Red
Lion Common Stock entitled to vote at the Special Meeting, and therefore the
Partnership has sufficient voting power to constitute a quorum and to approve
and adopt the Merger Agreement and the Merger, regardless of the vote of any
other stockholder. Pursuant to a separate agreement, the Partnership has agreed
to vote in favor of approval and adoption of the Merger Agreement and the
Merger. As a result, upon the vote of the Partnership in accordance with such
agreement, approval and adoption of the Merger Agreement and the Merger by the
stockholders of Red Lion is assured.
 
     Nevertheless, because of the significance to Red Lion of the Merger, your
participation in the Special Meeting, in person or by proxy, is important. IN
ORDER TO ENSURE THAT YOUR INTERESTS ARE REPRESENTED AT THE SPECIAL MEETING,
PLEASE COMPLETE, SIGN, DATE AND RETURN THE ACCOMPANYING PROXY IN THE ENCLOSED
ENVELOPE, WHETHER OR NOT YOU PLAN TO ATTEND THE SPECIAL MEETING. If you attend
the Special Meeting in person you may, if you wish, vote personally on all
matters brought before the Special Meeting even if you have previously returned
your Proxy.
 
                                          Sincerely,
 
                                          David J. Johnson
                                          Chairman of the Board,
                                          Chief Executive Officer and President