<PAGE>
                                                                   Exhibit 10.31


                                LETTER AMENDMENT


                                                    Dated as of January 23, 2002


To the banks, financial institutions and
   other institutional lenders (collectively,
   the "Lender Parties") parties to the Credit
   Agreement referred to below and to Bank of
   America, N.A., as administrative agent (the
   "Administrative Agent") for the Lender
   Parties


Ladies and Gentlemen:

                  We refer to the Amended and Restated Credit Agreement dated as
of August 20, 2001 among PacifiCare Health Systems, Inc., a Delaware
corporation, formerly known as N-T Holdings, Inc. (the "Borrower"), the
Subsidiary Guarantors parties thereto (together with the Borrower, the "Loan
Parties"), the banks, financial institutions and other institutional lenders
listed on the signature pages thereof as the Initial Lenders (the "Initial
Lenders"), the bank listed on the signature pages thereof as the Initial Issuing
Bank (the "Initial Issuing Bank" and, together with the Initial Lenders, the
"Initial Lender Parties") and the Swing Line Bank referred to therein, Banc of
America Securities LLC ("Banc of America Securities") and J.P. Morgan Securities
Inc. as co-lead arrangers (the "Co-Lead Arrangers"), Banc of America Securities,
J.P. Morgan Securities Inc. and Salomon Smith Barney Inc. as joint book-running
managers (the "Joint Book-Running Managers"), Bank of America, N.A. ("Bank of
America"), as collateral agent (together with any successor collateral agent
appointed pursuant to Article VII thereto, the "Collateral Agent"), and Bank of
America, as administrative agent (together with any successor administrative
agent appointed pursuant to Article VII thereto, the "Administrative Agent" and,
together with the Collateral Agent, the "Agents") for the Lender Parties
thereto, as amended by the Letter Amendment dated August 30, 2001 (such Amended
and Restated Credit Agreement, as amended hereby and as otherwise amended,
amended and restated, supplemented or modified from time to time, the "Credit
Agreement"). Capitalized terms not otherwise defined in this Letter Amendment
have the meanings specified in the Credit Agreement.

                  We hereby request that you agree to the following amendments:

                  (a) amend Section 1.01 to add the following new term:

                  "RESTRUCTURING CHARGES" has the meaning specified in Section
5.01(o).


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                           PacifiCare Letter Amendment
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                  (b) amend the definition of Net Income in Section 1.01 to
delete the "and" before clause (iii) and substitute a "," therefor and add new
clauses (iv) and (v) which read as follows: ", (iv) for purposes of the
covenants in Sections 5.04(a) and (b) and the definitions related thereto,
after-tax Restructuring Charges shall be excluded and (v) for purposes of
calculating Excess Cash Flow, any non-cash portion of Restructuring Charges
(other than any such charges that represent an accrual of future cash charges)
shall be excluded."

                  (c) amend Section 5.01(o) to the Credit Agreement in its
entirety to read in full as follows:

                  "(o) Appointment of Financial Consultant. Upon the earlier to
         occur of (i) an Event of Default or (ii) the reduction of Consolidated
         Net Income to less than zero in any 3 month rolling period (excluding
         the results from certain charges relating to the restructuring program
         implemented during the fourth quarter of 2001 (including, without
         limitation, the reduction in the Borrower's employee work force), to
         the extent deducted from revenues in calculating Net Income for such
         period in an amount not to exceed $60,000,000 (the "RESTRUCTURING
         CHARGES")) the Borrower shall appoint a financial consultant
         satisfactory to the Required Lenders that shall report to the Lenders
         through the coordination of the Administrative Agent."

                  (d) amend Section 5.01(p) to the Credit Agreement by deleting
the reference to 45 therein and substituting 60 therefor.

                  We agree to pay to the Administrative Agent, for the pro rata
benefit of the Lenders that execute this Letter Amendment by 5:00 p.m. (New York
time) on January 23, 2002, an amendment fee equal to 0.10% of the sum of the
outstanding principal balance of the Term A Advances and Revolving Credit
Commitments of such Lenders under the Credit Agreement as of the date hereof,
such fee payable once this Letter Amendment shall become effective, as specified
below.

                  The provisions of this Letter Amendment shall become effective
as of the date first above written, provided, however, that the Administrative
Agent shall have first received (i) counterparts of this Letter Amendment
executed by the Borrower and the Required Lenders and (ii) counterparts of the
Consent to this Letter Amendment executed by each Subsidiary Guarantor. Further,
it shall be a condition precedent to the effectiveness of this Letter Amendment
that the Borrower shall have paid all accrued fees of the Agents and the Lender
Parties (including, without limitation, the amendment fee referred to above for
this Letter Amendment).

                  The Borrower hereby confirms that on and as of the date hereof
and after giving effect to the terms of this Letter Amendment (i) the
representations and warranties contained in the Loan Documents are correct in
all material respects (other than any such representations and warranties, that,
by their terms, refer to a specific date), and (ii) no event has occurred and is
continuing which constitutes a Default.


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                           PacifiCare Letter Amendment
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                  The Credit Agreement and each of the other Loan Documents,
except to the extent they are modified by the amendment specifically set forth
above, are and shall continue to be in full force and effect and are hereby in
all respects ratified and confirmed. Without limiting the generality of the
foregoing, the Loan Documents and all of the Collateral described therein do and
shall continue to secure the payment of all Obligations of the Loan Parties
under the Loan Documents. The execution, delivery and effectiveness of this
Letter Amendment shall not, except as expressly provided herein, operate as a
waiver of any right, power or remedy of any Lender Party or the Administrative
Agent under the Credit Agreement or any other Loan Document, nor constitute a
waiver of any provision of the Credit Agreement or any other Loan Document.

                  If you agree to the terms and provisions of this Letter
Amendment, please evidence such agreement by executing and returning at least
two counterparts first via facsimile then by mail to Laurie Kolpinski at
Shearman & Sterling, 599 Lexington Avenue, New York, NY 10022, facsimile (212)
848-7179.

                  This Letter Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of a signature page to this Letter Amendment by telecopier shall be
effective as delivery of a manually executed counterpart of this Letter
Amendment.


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                           PacifiCare Letter Amendment
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                  This Letter Amendment shall be governed by, and construed in
accordance with, the laws of the State of New York.



                                        Very truly yours,


                                        PACIFICARE HEALTH SYSTEMS, INC.,
                                        as Borrower


                                        By ______________________________
                                           Title:


                           PacifiCare Letter Amendment
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                                        BANK OF AMERICA, N.A.,
                                        as Administrative Agent, Collateral
                                        Agent and as Initial Lender


                                        By ______________________________
                                           Title:


                           PacifiCare Letter Amendment
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Agreed as of the date first above written:


                                      __________________________________
                                      [Please type or print name of institution]

                                      By  ______________________________
                                          Title:


                           PacifiCare Letter Amendment
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                                     CONSENT


                                                    Dated as of January 23, 2002



           Each of the undersigned, as Subsidiary Guarantors under the Amended
and Restated Credit Agreement dated as of August 20, 2001, as amended by the
Letter Amendment dated August 30, 2001 (the "Credit Agreement") in favor of the
Lender Parties to the Credit Agreement referred to in the foregoing Letter
Amendment dated as of the date hereof, hereby consent to the said Letter
Amendment and hereby confirm and agree that the Subsidiary Guaranty is, and
shall continue to be, in full force and effect and is hereby ratified and
confirmed in all respects except that, upon the effectiveness of, and on and
after the date of, the said Letter Amendment, each reference in the Credit
Agreement to the Loan Documents or any "thereof", "thereunder", "thereof" or
words of like import shall mean and be a reference to the Loan Documents or such
Loan Document as amended by the said Letter Amendment.

                            [Signature pages follow]


                 PacifiCare Letter Amendment - Guarantor Consent
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                  IN WITNESS WHEREOF, each Subsidiary Guarantor has caused this
Consent to be duly executed and delivered by its officer thereunto duly
authorized as of the date first above written.

                                        PACIFICARE HEALTH PLAN
                                        ADMINISTRATORS, INC.,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                                        PACIFICARE eHOLDINGS, INC.,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                                        SENIORCO, INC.,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                                        RxCONNECT ACQUISITION CORPORATION,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                                        Rx SOLUTIONS, INC.,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                 PacifiCare Letter Amendment - Guarantor Consent
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                                        PACIFICARE BEHAVIORAL
                                        HEALTH, INC.,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                                        SECUREHORIZONS USA, INC.,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                                        PACIFICARE VENTURES, INC.,
                                        as Subsidiary Guarantor


                                        By  ______________________________
                                        Title:


                 PacifiCare Letter Amendment - Guarantor Consent