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                                                                   EXHIBIT 10.31


                         PACIFICARE HEALTH SYSTEMS, INC.
                             3120 LAKE CENTER DRIVE
                            SANTA ANA, CA 92704-6917

February 8, 2001


UniHealth Foundation
3400 Riverside Drive
Burbank, CA  91505
Attention: David R. Carpenter


RE:  MODIFICATION OF STOCK PURCHASE AGREEMENT

Ladies and Gentlemen:

This letter (the "Letter Agreement") is written to confirm our agreement
regarding the modification of the Stock Purchase Agreement dated May 4, 1999 by
and between PacifiCare Health Systems, Inc. ("PacifiCare") and UniHealth
Foundation ("UniHealth") (the "Stock Purchase Agreement"). Capitalized terms
used but not defined herein shall have the meanings given to them in the Stock
Purchase Agreement.

Under the Stock Purchase Agreement, PacifiCare agreed to purchase, and UniHealth
agreed to sell, most of the shares of PacifiCare Common Stock held by UniHealth,
subject to and in accordance with the terms of the Stock Purchase Agreement. The
parties have agreed upon certain modifications to the Stock Purchase Agreement.
The Stock Purchase Agreement is hereby modified as follows:

1.   PacifiCare agrees that, notwithstanding subsections 7.1(d) and 7.1(k) of
     the Stock Purchase Agreement, UniHealth may sell up to One Million
     (1,000,000) UniHealth Shares (the "Saleable Shares") in one or more open
     market sales or sales made pursuant to Rule 144 of the Securities Act of
     1933, as amended; provided, however, that UniHealth may not sell more than
     Two Hundred Fifty Thousand (250,000) UniHealth Shares on any given day. In
     connection with the modification to the Stock Purchase Agreement provided
     for in this paragraph 1, PacifiCare waives enforcement of any breach of the
     covenant set forth in subsection 7.1(l) of the Stock Purchase Agreement.

2.   PacifiCare waives any right of first refusal that it may have with respect
     to the Saleable Shares, provided that any such sale or disposition closes
     within thirty (30) days following February 9, 2001 and; provided, further,
     however, that UniHealth may not sell more than Two Hundred Fifty Thousand
     (250,000) UniHealth Shares on any given day. Any shares that UniHealth does
     not sell pursuant to this waiver shall remain subject to the right of first
     refusal under the Stock Purchase Agreement.

3.   In consideration for the right to sell the Saleable Shares granted in
     paragraph 1 above, UniHealth agrees that it will not exercise any right it
     may have pursuant to Section 9.2 of the Stock Purchase Agreement to sell to
     PacifiCare any of the Final Shares, and further

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     acknowledges and agrees that, upon execution of this Letter Agreement, any
     right to request that PacifiCare purchase the Final Shares will be
     terminated and extinguished in its entirety.

4.   Each of PacifiCare and UniHealth agree that, notwithstanding the definition
     of Final Closing Date set forth in Section 1.1(i) of the Stock Purchase
     Agreement, upon execution of this Letter Agreement, the Final Closing shall
     have occurred.

5.   Except as expressly stated herein, the Stock Purchase Agreement is and
     shall remain unmodified and in full force and effect.

6.   The Stock Purchase Agreement and any other agreements entered into
     contemporaneously therewith, together with this Letter Agreement, set forth
     the entire agreement of the parties and are intended to supersede all prior
     negotiations, understandings, and agreements and cannot be altered,
     amended, changed or modified in any respect or particular unless each such
     alteration, amendment, change or modification shall have been agreed to by
     PacifiCare and UniHealth and reduced to writing in its entirety and signed
     and delivered by each party.

7.   This Letter Agreement may be executed in counterparts, each of which
     together shall comprise one and the same instrument.


Please confirm your acceptance to the terms and provisions of this agreement by
signing below.



Very truly yours,

PACIFICARE HEALTH SYSTEMS, INC.


By:
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Its:
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AGREED AND ACCEPTED:

UNIHEALTH FOUNDATION

By:
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Its:                                         Date:
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