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                                                                   Exhibit 10.18


                                 LEASE GUARANTY

      THIS LEASE GUARANTY, dated as of December 28th, 2000 ("the Guaranty") is
made by Sierra Health Services, Inc., a Nevada corporation ("Guarantor") in
favor of CPSIEM, PLC, a Delaware limited liability company ("Landlord") with
reference to the following facts:

      A. Southwest Medical Associates, Inc., a Nevada corporation ("Tenant") is
a wholly owned subsidiary of the Guarantor;

      B. In order to induce Landlord to enter into a lease (the "Lease") of even
date herewith with Tenant covering the premises located at 2316 West Charleston
Boulevard, Las Vegas, Nevada, the Guarantor is executing and delivering this
Guaranty to Landlord;

      NOW, THEREFORE, in consideration of Landlord entering into the Lease, the
Guarantor hereby agrees as follows:

      l. Guarantee of Obligations

      (a) Guarantor hereby guarantees to Landlord the full and prompt payment
when due of all Basic Rent (as defined in the Lease), Additional Rent (as
defined in the Lease) and other charges payable by Tenant under the Lease, and
the full and prompt performance of all the covenants and conditions therein
provided to be performed by Tenant (the "Obligations"); and Guarantor does
hereby become surety to Landlord for all of the Obligations.

      (b) If a default (after giving effect to any applicable notice and cure
periods set forth in the Lease) shall at any time be made by Tenant, its
successors and assigns, in the payment of any such rent or other charges payable
by Tenant under the Lease or in performance of any of the covenants or
conditions contained in the Lease, Guarantor shall forthwith pay such rent or
other charges to Landlord and any arrears thereof, and will forthwith faithfully
perform all of such covenants and conditions, and will forthwith pay to Landlord
all damages and expenses actually incurred by Landlord that arise out of such
default by Tenant, its successors and assigns, under the Lease (including,
without limitation, all reasonable attorneys' fees incurred by Landlord or
caused by any such default or by the enforcement of this Guaranty and all late
charges incurred by Landlord under the Loan (hereafter defined). So long as
the Indenture (hereafter defined) has not been discharged or the Loan has not
been repaid in full, all payments due from Guarantor to Landlord hereunder shall
be made by Guarantor to Lender in accordance with section 15 hereof. After the
Indenture has been discharged and the Loan has been repaid in full, Guarantor
shall make all payments due to Landlord hereunder by wire transfer in
immediately available funds into the account specified by Landlord by notice to
Guarantor under section 8 hereof or if no such account has been specified, by
check delivered to Landlord at its address shown in the Lease.


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      (c) In addition, in case the Lease shall be terminated, modified or in any
way affected as a result of the rejection or disaffirmance thereof in any
bankruptcy, insolvency, reorganization, dissolution or similar proceeding,
Guarantor's obligations hereunder shall continue to the same extent as if the
Lease had not been so terminated, modified, rejected or disaffirmed. Guarantor
waives all rights and benefits which might accrue to it by reason of any such
proceeding, and Guarantor agrees that it shall be liable for the full amount of
the Obligations without regard to any limitation or discharge of liability of
Tenant that may result from any such proceeding.

      2. Unconditional Obligations. This Guaranty is a primary obligation of the
Guarantor and is an unconditional and absolute guarantee of payment and
performance (and not merely of collection) and the enforceability of this
Guaranty shall not be impaired or affected by any reduction, termination,
defense (other than the defense of prior payment or performance), offset,
counterclaim or recoupment whatsoever (all of which are hereby expressly waived
by Guarantor) irrespective of (a) the making of a demand, the institution of
suit or the taking of any other action to enforce Tenant's performance of the
Obligations, (b) the validity or enforceability of the Lease or any of the
Obligations or credit support therefor or right to offset with respect thereto
at any time held by Landlord, (c) any defense, set-off or counterclaim (other
than the defense of prior payment or performance) that may at any time be
available to Tenant or the Guarantor against Landlord, (d) any attempt to
collect from Tenant or any other entity or to perfect or enforce any security or
(e) upon any other action or circumstances whatsoever. The Guarantor waives any
requirement that Landlord shall have instituted any action or proceeding or
taken any steps to enforce any rights against Tenant or any other person or
entity to compel any such performance or to collect such amount pursuant to the
provisions of the Lease or at law or in equity.

      3. Amendments, etc., with Respect to the Obligations. The Guarantor shall
remain obligated hereunder notwithstanding that, without any reservation of
rights against Guarantor and without notice to or further assent by Guarantor,
(a) any demand for payment or performance of any of the Obligations made by
Landlord may be rescinded by Landlord and any of the other Obligations continue
to be in effect; (b) the Obligations and any collateral security or guarantee
therefor or right of offset with respect thereto, may be renewed, modified,
accelerated, waived, or released by Landlord; and (c) the Lease or other
guarantee or document executed and delivered in connection therewith may be
modified or terminated, in accordance with its terms, as the parties thereto may
deem advisable. Landlord shall not have any obligation to secure, perfect or
insure any lien at any time held as security for the Obligations or for this
Guaranty or any property subject thereto. For purposes hereof, "demand" shall
include, without limitation, the commencement and continuance of any legal
proceedings.

      4. The Guarantor's Obligations Not Affected. The duties and obligations of
the Guarantor under this Guaranty shall remain in full force and effect, without
the necessity of any


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reservation of rights against the Guarantor or notice to the Guarantor and shall
not be impaired or discharged by:

      (a) any failure to enforce any right, power or remedy with respect to the
Obligations,

      (b) the lack of genuineness, unenforceability or invalidity of the
Obligations or the lack of genuineness, unenforceability or invalidity of any
agreement relating thereto;

      (c) any change in the ownership of Tenant or the insolvency, bankruptcy or
any other change in the legal status of Tenant, Landlord or Guarantor or any
rejection or modification of the Obligations of Tenant or those of any person as
a result of any bankruptcy, reorganization or similar proceeding;

      (d) the existence of any claim, set off or other rights or defenses (other
than the defense of prior payment or performance) that the Guarantor may have at
any time against Tenant or Landlord or any other person and the existence of any
claim, setoff or other rights or defenses that Tenant may have against
Guarantor, Landlord or any other person in connection with the Lease or with an
unrelated transaction;

      (e) any merger or consolidation of Tenant or the Guarantor with any other
entity, or any sale, lease or transfer of any or all of the assets of Tenant or
the Guarantor to any other entity;

      (f) the rights, powers or privileges Landlord may now or hereafter have
against any person or collateral;

      (g) any defect in title, condition or fitness of use of the Premises (as
defined in the Lease), any casualty or condemnation affecting the Premises or
any sublease, assignment, renewal, or other transfer or continuation of Tenant's
rights under the Lease or any other Obligations, whether in accordance with the
terms of the Lease or otherwise; or

      (h) any other action, omission, occurrence or circumstance whatsoever
which may in any manner or to any extent vary the risk or effect a legal or
equitable defense or discharge of the Guarantor hereunder as a matter of law or
otherwise.

      5. Waiver by the Guarantor. The Guarantor unconditionally waives and
releases, to the fullest extent permitted by applicable law (a) notice of the
acceptance of this Guaranty and of any change in Tenant's financial condition;
(b) notices of the creation, renewal, extension or accrual of any Obligation or
acceptance of this Guaranty (the Obligations shall conclusively be deemed to
have been created, renewed, amended or waived in reliance upon this Guaranty and
all dealings between Tenant, the Guarantor and Landlord shall be conclusively
presumed to have


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been had in reliance upon this Guaranty); (c) notices which may be required by
statute, rule of law or otherwise, now or hereafter in effect, to preserve
intact any rights of Landlord against the Guarantor; (d) the right to interpose
all substantive and procedural defenses of the law of guaranty, indemnification
and suretyship, except the defenses of prior payment or prior performance by
Tenant or the Guarantor of the Obligations; (e) all rights and remedies accorded
by applicable laws and regulations to guarantors or sureties, including any
extension of time conferred by any law now or hereafter in effect; (f) any right
or claim of right to cause a marshaling of Tenant's assets or to cause Landlord
to proceed against Tenant or any collateral held by Landlord at any time or in
any particular order; (g) rights to the endorsement, assertion or exercise by
Landlord of any right, power, privilege or remedy conferred herein or in the
Lease or otherwise; (h) requirements of promptness or diligence on the part of
Landlord; (i) any notices of the sale, transfer or other disposition of any
right, title to or interest in the Premises or the Lease; (j) rights and
defenses arising out of an election of remedies by Landlord even though that
election of remedies has destroyed the Guarantor's rights of subrogation and
reimbursement against Tenant by operation of law or otherwise; or (k) other
circumstances whatsoever (except the defenses of prior payment or prior
performance by Tenant or the Guarantor of the Obligations) which might otherwise
constitute a legal or equitable discharge, release or defense of a guarantor or
surety, or which might otherwise limit recourse against the Guarantor. No
failure to exercise and no delay in exercising, on the part of Landlord, any
right, power or privilege hereunder shall operate as a waiver thereof, nor shall
any single or partial exercise of any right, power or privilege preclude any
other or further exercise thereof, or the exercise of any other power or right.
The rights and remedies herein provided are cumulative and not exclusive of any
rights or remedies provided by law.

      6. Reinstatement. This Guaranty shall continue to be effective, or be
reinstated, as the case may be, if at any time payment, in whole or in part, of
any of the Obligations (i) is rescinded or must otherwise be restored or
returned by Landlord upon the bankruptcy, insolvency, reorganization,
dissolution, or the like, of Tenant or the Guarantor, or as a result of, the
appointment of a receiver, trustee or other officer with similar powers with
respect to Tenant or the Guarantor or any substantial part of either's
respective property, or otherwise, or (ii) is returned to Tenant or Guarantor by
reason of a decree, moratorium or other sovereign act of any governmental
authority, in each case, all as though such payment had not been made
notwithstanding any termination of this Guaranty or the Lease.

      7. Representations and Warranties of the Guarantor. The Guarantor
represents and warrants to Landlord that as of the date hereof:

      (a) The execution and delivery of this Guaranty by Guarantor has been in
all respects authorized and approved by Guarantor; Guarantor has full power and
authority to enter into this Guaranty; each party acting on its behalf in
connection with the delivery of this Guaranty is duly authorized to execute and
deliver this Guaranty and to execute and deliver each of the


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documents, certificates, affidavits and instruments to which it is a party in
connection with the transaction described herein; and each such document,
certificate, affidavit and instrument, including without limitation this
Guaranty, is valid and binding against Guarantor, and enforceable in accordance
with its terms.

      (b) Guarantor is free from bankruptcy, reorganization or arrangement
proceedings and has not made a general assignment for the benefit of creditors,
and to the best of its knowledge and belief, no such proceedings or assignment
is pending or threatened against it.

      (c) Certain of Guarantor's regulated subsidiaries have a "financial
strength" rating from Fitch IBCA, Inc. of BB+.

      8. Notices. All notices required or permitted by the terms hereof shall be
in writing and shall be given in accordance with Section 6.1 of the Lease with a
copy to Lender and, in the case of the Guarantor, shall be addressed and sent to
Sierra Health Services, Inc., 2716 N. Tenaya Way, Las Vegas, Nevada 89128, Attn:
Administrative Services, with a copy to Tenant.

      9. Amendments and Waivers; Successors and Assigns.

      (a) This Guaranty may not be amended except by an instrument in writing
signed by the Guarantor and Landlord.

      (b) This Guaranty shall be binding upon the Guarantor and its successors
and assigns and shall inure to the benefit of Landlord and its successors and
assigns.

      10. Termination. Subject to the provisions of Section 6 hereof, this
Guaranty shall remain in full force and effect until the date on which all
Obligations and the obligations of the Guarantor hereunder shall have been
satisfied by indefeasible payment and performance in full.

      11. Entire Agreement. This Guaranty constitutes the entire agreement and
supersedes all prior agreements and understandings, both written and oral
between or among the Guarantor, Tenant and Landlord with respect to the subject
matter hereof.

      12. WAIVER OF JURY TRIAL. GUARANTOR HEREBY IRREVOCABLY AND UNCONDITIONALLY
WAIVES TRIAL BY JURY IN ANY LEGAL ACTION OR PROCEEDING RELATING TO THIS
GUARANTY.

      13. Governing Law. This Guaranty shall in all respects be governed by the
laws of the State of Nevada. Guarantor consents to venue and jurisdiction in any
state or federal court located in Clark County, Nevada, and waives any defense
of forum non conveniens.


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      14. Subrogation. So long as this Guaranty is in effect, Guarantor shall
have no rights (direct or indirect) of subrogation, contribution, reimbursement,
indemnification or other rights of payment or recovery from any person or entity
(including, without limitation, the Tenant) for any payments made by the
Guarantor hereunder.

      15. Guarantor Consent to Assignment. Landlord has assigned its rights
under this Guaranty to Heller Healthcare Finance, Inc., a Delaware corporation
(collectively, with its successors and assigns, "Lender") pursuant to that
certain Deed of Trust and Assignment of Rents of even date herewith (singly and
collectively, as the same may be amended from time to time together with all
replacements thereof, the "Indenture"). The Indenture secures repayment of a
loan, which loan including all accrued interest and other amounts payable
thereunder by Landlord is referred to herein as the "Loan". Guarantor hereby
acknowledges the assignment to Lender of all amounts to be paid by Guarantor to
Landlord under this Guaranty, and all other rights, powers and remedies, but
none of the obligations, of Landlord under this Guaranty and confirms that this
Guaranty shall remain in full force and effect.

      (a) So long as the Indenture has not been discharged and the Loan has not
been repaid in full, Landlord irrevocably authorizes and directs Guarantor, and
Guarantor hereby agrees:

      (i) to pay to Lender all amounts due or to become due and payable by
Guarantor to Landlord under this Guaranty in immediately available United
States Dollar denominated funds by wire transfer into the account referenced in
Exhibit A attached hereto or to such other account as Lender shall specify by
notice to Guarantor not less than seven days prior to the effectiveness of any
such change of account;

      (ii) to accept any notices, waivers or consents given and actions taken on
behalf of Landlord by Lender, and Guarantor agrees that: (A) notices, waivers
and consents given on behalf of Landlord by Lender shall have the same force and
effect as notices, waivers and consents given by Landlord, and (B) in the event
of inconsistent notices, waivers or consents from Landlord and Lender, notices,
waivers and consents from Lender shall control. In no event shall Guarantor have
any liability to Landlord based upon any action taken or omitted to be taken by
Guarantor in reliance upon any notice, waiver or consent received by Guarantor
from Lender.

      (b) Guarantor agrees that so long as the Indenture has not been discharged
and the Loan has not been repaid in full, this Guaranty shall not be modified or
terminated without the prior written consent of Lender.

      (c) Guarantor agrees that if Lender or its designee acquires title to the
Premises (as defined in the Lease), Landlord's interest thereunder is freely
assignable by Lender to any person without the consent of Guarantor and, upon
any such assignment, Guarantor shall affirm its obligations under this Guaranty
in writing upon reasonable prior request by Lender or its


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designee. Guarantor waives any defense based on a termination of the Lease
following a foreclosure (or similar proceeding) with respect to the Premises.

      (d) Concurrently herewith, Lender and Tenant have executed a
Subordination, Non-Disturbance and Attornment Agreement ("SNDA"). Guarantor
hereby waives any defense based on the assertion that the terms of the tenancy
have changed (or a new tenancy has been created) by operation of the SNDA in any
respect, including without limitation following a foreclosure or similar
proceeding.

      16. Financial Statements; Certificates. Guarantor will cause to be
delivered to Landlord and Lender, for itself, each of the financial statements,
notices and other information required to be delivered by Tenant pursuant to
Section 6.2(b) of the Lease. In addition, Guarantor agrees upon prior written
request to meet with Landlord and Lender during normal business hours at
mutually convenient times, from time to time, to discuss such information about
Guarantor's business and financial condition requested by Landlord or Lender.

      IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be executed
as of the day and year first set forth above.

SIERRA HEALTH SERVICES, INC., a Nevada corporation

By: /s/ Frank Collins
    --------------------------------
Name:

Title:


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                                   EXHIBIT A

                  LENDER'S WIRE TRANSFER INFORMATION

Mellon Bank (Pittsburgh, Pennsylvania), ABA No.: 043000261, Account Name: Heller
Healthcare Finance, Inc., Account No.: 078-7384. All such payments should
reference Loan No. 20-401.



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