<PAGE>

                                                                     EXHIBIT 4.6

                             SUPPLEMENTAL INDENTURE

         SUPPLEMENTAL INDENTURE (this "Supplemental Indenture") dated as of
September 29, 2000, among IASIS Finance, Inc., a Delaware corporation (the
"Guaranteeing Subsidiary"), a subsidiary of IASIS Healthcare Corporation, a
Delaware corporation (the "Company"), and The Bank of New York, as trustee under
the indenture referred to below (the "Trustee").

                              W I T N E S S E T H:

         WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture (the "Indenture"), dated as of October 15, 1999, providing
for the issuance of an aggregate principal amount at maturity of $230,000,000 of
13% Senior Subordinated Notes due 2009 (the "Notes");

         WHEREAS, the Indenture provides that under certain circumstances the
Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental
indenture pursuant to which the Guaranteeing Subsidiary shall unconditionally
guarantee all of the Company's Obligations under the Notes and the Indenture on
the terms and conditions set forth herein (the "Subsidiary Guarantee"); and

         WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

         NOW THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the
Guaranteeing Subsidiary and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Notes as follows:

         1.       Capitalized Terms. Capitalized terms used herein without
definition shall have the meanings assigned to them in the Indenture.

         2.       Agreement to Guarantee. The Guaranteeing Subsidiary hereby
agrees as follows:

                  (a)      Along with all Guarantors named in the Indenture, to
         jointly and severally Guarantee to each Holder of a Note authenticated
         and delivered by the Trustee and to the

<PAGE>

         Trustee and its successors and assigns, irrespective of the validity
         and enforceability of the Indenture, the Notes or the obligations of
         the Company hereunder or thereunder, that:

                           (i)      the principal of and interest on the Notes
                  will be promptly paid in full when due, whether at maturity,
                  by acceleration, redemption or otherwise, and interest on the
                  overdue principal of and interest on the Notes, if any, if
                  lawful, and all other obligations of the Company to the
                  Holders or the Trustee hereunder or thereunder will be
                  promptly paid in full or performed, all in accordance with the
                  terms hereof and thereof; and

                           (ii)     in case of any extension of time of payment
                  or renewal of any Notes or any of such other obligations, that
                  same will be promptly paid in full when due or performed in
                  accordance with the terms of the extension or renewal, whether
                  at stated maturity, by acceleration or otherwise. Failing
                  payment when due of any amount so guaranteed or any
                  performance so guaranteed for whatever reason, the Guarantors
                  shall be jointly and severally obligated to pay the same
                  immediately.

                  (b)      The obligations hereunder shall be unconditional,
         irrespective of the validity, regularity or enforceability of the Notes
         or the Indenture, the absence of any action to enforce the same, any
         waiver or consent by any Holder of the Notes with respect to any
         provisions hereof or thereof, the recovery of any judgment against the
         Company, any action to enforce the same or any other circumstance which
         might otherwise constitute a legal or equitable discharge or defense of
         a guarantor.

                  (c)      The following is hereby waived: diligence
         presentment, demand of payment, filing of claims with a court in the
         event of insolvency or bankruptcy of the Company, any right to require
         a proceeding first against the Company, protest, notice and all demands
         whatsoever.

                  (d)      This Subsidiary Guarantee shall not be discharged
         except by complete performance of the obligations contained in the
         Notes and the Indenture.

                                       2

<PAGE>

                  (e)      If any Holder or the Trustee is required by any court
         or otherwise to return to the Company, the Guarantors, or any
         Custodian, Trustee, liquidator or other similar official acting in
         relation to either the Company or the Guarantors, any amount paid by
         either to the Trustee or such Holder, this Subsidiary Guarantee, to the
         extent theretofore discharged, shall be reinstated in full force and
         effect.

                  (f)      The Guaranteeing Subsidiary shall not be entitled to
         any right of subrogation in relation to the Holders in respect of any
         obligations guaranteed hereby until payment in full of all obligations
         guaranteed hereby.

                  (g)      As between the Guarantors, on the one hand, and the
         Holders and the Trustee, on the other hand, (x) the maturity of the
         obligations guaranteed hereby may be accelerated as provided in Article
         6 of the Indenture for the purposes of this Subsidiary Guarantee,
         notwithstanding any stay, injunction or other prohibition preventing
         such acceleration in respect of the obligations guaranteed hereby, and
         (y) in the event of any declaration of acceleration of such obligations
         as provided in Article 6 of the Indenture, such obligations (whether or
         not due and payable) shall forthwith become due and payable by the
         Guarantors for the purpose of this Subsidiary Guarantee.

                  (h)      The Guarantors shall have the right to seek
         contribution from any non-paying Guarantor so long as the exercise of
         such right does not impair the rights of the Holders under the
         Guarantee.

                  (i)      The obligations hereunder shall be subject to the
         subordination provisions of the Indenture.

         3.       Execution and Delivery. Each Guaranteeing Subsidiary agrees
that the Subsidiary Guarantees shall remain in full force and effect
notwithstanding any failure to endorse on each Note a notation of such
Subsidiary Guarantee.

         4.       Guaranteeing Subsidiary May Consolidate, Etc. on Certain
Terms.

                  (a)      The Guaranteeing Subsidiary may not consolidate with
         or merge with or into (whether or not such Guarantor is

                                       3

<PAGE>

         the surviving Person) another corporation, Person or entity whether or
         not affiliated with such Guarantor unless:

                           (i)      subject to Section 11.05 of the Indenture,
                  the Person formed by or surviving any such consolidation or
                  merger (if other than a Guarantor or the Company)
                  unconditionally assumes all the obligations of such Guarantor,
                  pursuant to a supplemental indenture in form and substance
                  reasonably satisfactory to the Trustee, under the Notes, the
                  Indenture and the Subsidiary Guarantee on the terms set forth
                  herein or therein; and

                           (ii)     immediately after giving effect to such
         transaction, no Default or Event of Default exists.

                  (b)      In case of any such consolidation, merger, sale or
         conveyance and upon the assumption by the successor corporation, by
         supplemental indenture, executed and delivered to the Trustee and
         satisfactory in form to the Trustee, of the Subsidiary Guarantee
         endorsed upon the Notes and the due and punctual performance of all of
         the covenants and conditions of the Indenture to be performed by the
         Guarantor, such successor corporation shall succeed to and be
         substituted for the Guarantor with the same effect as if it had been
         named herein as a Guarantor. Such successor corporation thereupon may
         cause to be signed any or all of the Subsidiary Guarantees to be
         endorsed upon all of the Notes issuable hereunder which theretofore
         shall not have been signed by the Company and delivered to the Trustee.
         All the Subsidiary Guarantees so issued shall in all respects have the
         same legal rank and benefit under the Indenture as the Subsidiary
         Guarantees theretofore and thereafter issued in accordance with the
         terms of the Indenture as though all of such Subsidiary Guarantees had
         been issued at the date of the execution hereof.

                  (c)      Except as set forth in Articles 4 and 5 of the
         Indenture, and notwithstanding clauses (a) and (b) above, nothing
         contained in the Indenture or in any of the Notes shall prevent any
         consolidation or merger of a Guarantor with or into the Company or
         another Guarantor, or shall prevent any sale or conveyance of the
         property of a Guarantor as an entirety or substantially as an entirety
         to the Company or another Guarantor.

                                       4

<PAGE>

         5.       Releases.

                  (a)      In the event of a sale or other disposition of all of
         the assets of any Guarantor, by way of merger, consolidation or
         otherwise, or a sale or other disposition of all to the capital stock
         of any Guarantor, then such Guarantor (in the event of a sale or other
         disposition, by way of merger, consolidation or otherwise, of all of
         the capital stock of such Guarantor) or the corporation acquiring the
         property (in the event of a sale or other disposition of all or
         substantially all of the assets of such Guarantor) will be released and
         relieved of any obligations under its Subsidiary Guarantee; provided
         that the Net Proceeds of such sale or other disposition are applied in
         accordance with the applicable provisions of the Indenture, including
         without limitation Section 4.10 of the Indenture. Upon delivery by the
         Company to the Trustee of an Officers' Certificate and an Opinion of
         Counsel to the effect that such sale or other disposition was made by
         the Company in accordance with the provisions of the Indenture,
         including without limitation Section 4.10 of the Indenture, the Trustee
         shall execute any documents reasonably required in order to evidence
         the release of any Guarantor from its obligations under its Subsidiary
         Guarantee.

                  (b)      Any Guarantor not released from its obligations under
         its Subsidiary Guarantee shall remain liable for the full amount of
         principal of and interest on the Notes and for the other obligations of
         any Guarantor under the Indenture as provided in Article 11 of the
         Indenture.

         6.       No Recourse Against Others. No past, present or future
director, officer, employee, incorporator, stockholder or agent of the
Guaranteeing Subsidiary, as such, shall have any liability for any obligations
of the Company or any Guaranteeing Subsidiary under the Notes, any Subsidiary
Guarantees, the Indenture or this Supplemental Indenture or for any claim based
on, in respect of, or by reason of, such obligations or their creation. Each
Holder of the Notes by accepting a Note waives and releases all such liability.
The waiver and release are part of the consideration for issuance of the Notes.
Such waiver may not be effective to waive liabilities under the federal
securities laws and it is the view of the SEC that such a waiver is against
public policy.

                                       5

<PAGE>

         7.       NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW
YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT
WITHOUT GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT
THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED
THEREBY.

         8.       Counterparts. The parties may sign any number of copies of
this Supplemental Indenture. Each signed copy shall be an original, but all of
them together represent the same agreement.

         9.       Effect of Headings. The Section headings herein are for
convenience only and shall not affect the construction hereof.

         10.      The Trustee. The Trustee shall not be responsible in any
manner whatsoever for or in respect of the validity or sufficiency of this
Supplemental Indenture or for or in respect of the recitals contained herein,
all of which recitals are made solely by the Guaranteeing Subsidiary and the
Company.

         IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed and attested, all as of the date first above
written.

         Dated: September 29, 2000

                                 IASIS FINANCE, INC.

                                 By: /s/ John K. Crawford
                                     -----------------------------------
                                     Name: John K. Crawford
                                     Title: Executive Vice President and
                                            Chief Financial Officer

                                 THE BANK OF NEW YORK,
                                   as Trustee

                                 By: /s/ Robert A. Massimillo
                                     -------------------------------
                                     Name: Robert A. Massimillo
                                     Title: Assistant Vice President

                                       6