SC 13D

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

SIERRA HEALTH SERVICES, INC.

(Name of Issuer)

Common Stock (par value $.005)

(Title of Class of Securities)

826322109

(CUSIP Number)

Dannette L. Smith

Deputy General Counsel and Assistant Secretary

UnitedHealth Group Incorporated

9900 Bren Road East

Minnetonka, Minnesota

(952) 936-1300

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

March 11, 2007

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ¨

NOTE: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §§240.13d-7 for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

1	NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
	UnitedHealth Group Incorporated
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)  ¨
	(b)  x*
3	SEC USE ONLY
4	SOURCE OF FUNDS
	Not applicable
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) or 2(e)	¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Minnesota

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7   SOLE VOTING POWER
	0
	8  SHARED VOTING POWER
	4,372,080**
	9  SOLE DISPOSITIVE POWER
	0
	10  SHARED DISPOSITIVE POWER
	4,372,080**

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	4,372,080
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES	¨
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	7.9%
14	TYPE OF REPORTING PERSON
	CO

* See Item 4.

** Pursuant to Rule 13d-4 of the Act, the Reporting Person disclaims beneficial ownership of such shares, and this Statement shall not be construed as an admission that the Reporting Person is the beneficial owner of any securities covered by this Statement.

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Item 1. Security and Issuer.

This Statement on Schedule 13D (this “Statement”) relates to the common stock, par value $.005, of Sierra Health Services, Inc., a corporation organized under the laws of the State of Nevada (the “Company”). The Company’s principal executive offices are located at 2724 North Tenaya Way, Nevada 89128.

Item 2. Identity and Background.

This Statement is filed by UnitedHealth Group Incorporated, a corporation organized under the laws of the State of Minnesota (“UNH”). The principal executive offices of UNH are located at UnitedHealth Group Center, 9900 Bren Road East, Minnetonka, Minnesota. For information required by General Instruction C to Schedule 13D with respect to the directors and executive officers of UNH, reference is made to Exhibit 1 hereto and incorporated herein by reference.

During the last five years, neither UNH nor, to the best of its knowledge, any persons listed on Exhibit 1 hereto, has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and, as a result of such proceeding, was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Item 3. Source and Amount of Funds or Other Consideration.

Anthony M. Marlon (the “Stockholder”), on the one hand and solely in his individual capacity as a stockholder of the Company, and UNH, on the other hand, has entered into a Voting and Support Agreement (described in Item 4 of this Statement and copy of which is attached hereto as Exhibit 2) (the “Voting Agreement”) with respect to certain shares of the Company’s common stock beneficially owned by the Stockholder (the “Shares”). No shares of the Company’s common stock were purchased by UNH pursuant to the Voting Agreement, and thus no funds were used for such purpose. Exhibit 2 is specifically incorporated herein by reference in response to this Item 3.

Item 4. Purpose of Transaction.

The purpose of UNH’s entering into the Voting Agreement covering the Shares to which this Statement relates is to facilitate the transactions contemplated by the Agreement and Plan of Merger, dated as of March 11, 2007, by and among UNH, Sapphire Acquisition, Inc. (“Merger Sub”) and the Company, Exhibit 3 hereto (the “Merger Agreement”). Except as otherwise provided in this Statement, capitalized terms that are used but not otherwise defined in this Statement shall have the meaning assigned to such terms in the Merger Agreement.

Pursuant to the Instructions for Cover Page (2) to Schedule 13D, the following is a description of the relationship among UNH and the Stockholder under the Voting Agreement, but is not an affirmation by UNH of the existence of a group for purposes of Section 13(d)(3) or Section 13(g)(3) of the Act or Rule 13d-5(b)(1) thereunder. Pursuant to Rule 13d-4 of the Act, UNH disclaims beneficial ownership of the Shares.

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As a condition to entering into the Merger Agreement, UNH required that the Stockholder enter into, and the Stockholder agreed to enter into, the Voting Agreement. Pursuant to the Voting Agreement, the Stockholder agreed, among other things, to vote (or cause to be voted), in person or by proxy, or deliver a written consent (or cause a consent to be delivered) covering, all the Shares and any shares of the Company’s common stock acquired by the Stockholder after the date of the Voting Agreement and any other voting securities of the Company (whenever acquired) that are owned beneficially or of record by the Stockholder or as to which he has, directly or indirectly, the right to vote or direct the voting, (i) in favor of approval of the Merger Agreement and any other action of the Company’s stockholders requested in furtherance of the transactions contemplated by the Merger Agreement, and (ii) against any action or agreement submitted for approval of the stockholders of the Company that would reasonably be expected to result in a material breach of any covenant, representation or warranty or any other obligation or agreement of (A) the Company contained in the Merger Agreement that is reasonably likely to result in any of the conditions to Parent’s or Merger Sub’s obligations under the Merger Agreement not being fulfilled and (B) the Stockholder contained in the Voting Agreement; and (iii) against any Company Takeover Proposal (as defined in the Voting Agreement) or any other action, agreement or transaction submitted for approval to the stockholders of the Company that the Stockholder would reasonably expect is intended, or would reasonably be expected, to materially impede, interfere with, delay, postpone, discourage or adversely affect the Merger or the Voting Agreement.

The Stockholder has also granted UNH an irrevocable proxy coupled with an interest to vote the Shares as provided for in the Voting Agreement. The proxy will expire automatically and without further action by the parties upon the termination of the Voting Agreement. The Voting Agreement will terminate upon the earlier to occur of (a) the Effective Time and (b) the date and time of termination of the Merger Agreement by either or both of UNH and the Company pursuant to Section 8.1 of the Merger Agreement.

The Merger Agreement provides that, upon the terms and subject to the conditions set forth in the Merger Agreement, Merger Sub will merge with and into the Company (the “Merger”), with the Company continuing as the surviving company. At the effective time of the Merger, each issued and outstanding share of common stock of the Company (other than shares owned by UNH or Merger Sub, which shares will be cancelled), will be converted into the right to receive $43.50 in cash, on the terms specified in the Merger Agreement.

Completion of the Merger is subject to various conditions, including, among others, (i) approval of the holders of a majority of the outstanding shares of common stock, (ii) expiration or termination of the applicable Hart-Scott-Rodino Act waiting period, (iii) absence of any order, injunction or other judgment or decree prohibiting the consummation of the Merger, (iv) receipt of required governmental consents and approvals without negative regulatory action, and (v) subject to certain exceptions, the accuracy of the representations and warranties of the Company and UNH, as applicable, and compliance by the Company and UNH with their respective obligations under the Merger Agreement.

The Merger Agreement contains certain termination rights for the Company and UNH, and further provides that, upon termination of the Merger Agreement under specified circumstances, the Company may be required to pay UNH a termination fee of $85.0 million and in other circumstances, UNH may be required to pay the Company a termination fee of $25.0 million.

After the effective time of the Merger, UNH intends to cause the Company’s common stock to be delisted from the New York Stock Exchange, and may take one or more of the other actions described in the instructions to Item 4 of Schedule 13D.

The foregoing descriptions of the transactions contemplated by the Voting Agreement and the Merger Agreement are qualified in their entirety by reference to the respective agreements (Exhibits 2 and 3, respectively, to this Statement). Exhibits 2 and 3 are specifically incorporated herein by reference in answer to this Item 4.

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Except as set forth in this Statement, the Voting Agreement and the Merger Agreements, neither UNH nor, to the best of its knowledge, any of the individuals named in Exhibit 1 hereto, has any plans or proposals that relate to or would result in or relate to any of the actions specified in subparagraphs (a) through (j) of Item 4 of Schedule 13D.

Item 5. Interest in Securities of the Issuer.

(a) As a result of the Voting Agreement, UNH may be deemed to have beneficial ownership of an aggregate of 4,372,080 shares of the Company’s common stock, which constitute, based on information set forth in the Merger Agreement and assuming the exercise of all shares subject to options included in the foregoing number of shares, approximately 7.9% of the outstanding shares of voting stock of the Company. UNH, however, hereby disclaims beneficial ownership of the Shares, and this Statement shall not be construed as an admission that UNH, for any or all purposes, is the beneficial owner of the Shares.

Other than as provided above, neither UNH, nor, to the best of UNH’s knowledge, any of the persons listed on Exhibit 1 hereto, owns or has any right to acquire, directly or indirectly, any shares of the Company’s common stock.

(b) Pursuant to the Voting Agreement, UNH may be deemed to have shared power to vote and dispose of 4,372,080 shares with Anthony M. Marlon (including, according to the Voting Agreement, 3,826,954 shares held indirectly through a total of four trusts established by the Stockholder and his wife, 3,000 shares held indirectly through a limited partnership, 305,296 shares held indirectly by the AMM&RM Family Limited Partnership and 212,830 held for the Stockholder’s account under the Company’s 401(k) plan and 24,000 shares subject to stock options outstanding as of March 11, 2007). UNH, however, (i) is not entitled to any rights as a stockholder of the Company as to the Shares, except pursuant to the proxies granted under the Voting Agreement, and (ii) disclaims any beneficial ownership of the Shares.

The information required by Item 2 relating to the Stockholder is set forth in Exhibit 4 and consists of information contained in the Proxy Statement on Schedule 14A filed by the Company on April 13, 2006. Although UNH has no reason to believe that such information was not reliable as of its date, UNH only accepts responsibility for accurately reproducing such information and accepts no further or other responsibility for such information. In addition, UNH makes no representation or warranty with respect to the accuracy or completeness of such information or any representation or warranty, and the filing of this Statement shall not create any implication under any circumstances that there have been no events, or that there is no other information, including events or information not yet publicly disclosed by the Stockholder, which may affect the accuracy or completeness of such information.

(c) Except with respect to the transactions contemplated by the Voting Agreement and the Merger Agreement, neither UNH, nor, to the best of UNH’s knowledge, any of the persons listed on Exhibit 1 hereto, has effected any transaction in the Company’s common stock during the past 60 days. The descriptions of the transactions contemplated by the Voting Agreement and the Merger Agreement are qualified in their entirety by reference to the respective agreements (Exhibits 2 and 3, respectively, to this Statement). Exhibits 2 and 3 to this Statement are specifically incorporated herein by reference in answer to this Item 5.

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(d) Except as set forth in this Item 5, no other person is known by UNH to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the common stock of the Company that may be deemed to be beneficially owned by UNH as provided for herein.

(e) Not applicable.

Item 6. Contracts, Arrangements, Understanding or Relationships with Respect to Securities of the Issuer.

See “Item 4. Purpose of Transaction” for a description of the Voting Agreement and the Merger Agreement, which is qualified in its entirety by reference to the respective agreements,(Exhibits 2 and 3, respectively, to this Statement). Exhibits 2 and 3 are specifically incorporated herein by reference in answer to this Item 6.

Item 7. Material To Be Filed as Exhibits.

Exhibit	Description
1.	Directors and Executive Officers of UnitedHealth Group Incorporated
2.	Voting and Support Agreement dated as of March 11, 2007, between UnitedHealth Group Incorporated and Anthony M. Marlon
3.	Agreement and Plan of Merger dated as of March 11, 2007, by and among UnitedHealth Group Incorporated, Sapphire Acquisition, Inc. and Sierra Health Services, Inc., and incorporated by reference to Exhibit 2.1 of Sierra Health Services, Inc.’s Current Report on Form 8-K filed on March 13, 2007
4.	Certain Information Regarding the Stockholder

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SIGNATURE

After reasonable inquiry and to the best knowledge and belief of the undersigned, the undersigned certifies that the information set forth in this statement is true, complete and correct.

Date: March 20, 2007

UNITEDHEALTH GROUP INCORPORATED
By:	/s/ Dannette L. Smith
Name:	Dannette L. Smith
Title:	Deputy General Counsel and Assistant Secretary

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EXHIBIT INDEX

Exhibit	Description
Exhibit 1	Directors and Executive Officers of UnitedHealth Group Incorporated
Exhibit 2	Voting and Support Agreement, dated as of March 11, 2007, between UnitedHealth Group Incorporated and Anthony M. Marlon
Exhibit 3	Agreement and Plan of Merger dated as of March 11, 2007, by and among UnitedHealth Group Incorporated, Sapphire Acquisition, Inc. and Sierra Health Services, Inc., and incorporated by reference to Exhibit 2.1 of Sierra Health Services, Inc.’s Current Report on Form 8-K filed on March 13, 2007
Exhibit 4	Certain Information Regarding the Stockholder

EX-99.1

EXHIBIT 1

DIRECTORS AND EXECUTIVE OFFICERS OF UNH CORP

The following table sets forth the name and present principal occupation or employment, and the name, principal business and address of any corporation or other organization in which such occupation or employment is conducted of each director and executive officer of UNH. All of the directors and executive officers are citizens of the United States, except for Mr. Leatherdale, who is a citizen of Canada.

DIRECTORS OF UNH	PRESENT PRINCIPAL OCCUPATION	ADDRESS
Richard T. Burke	Non-executive Chairman of UNH	9900 Bren Road East Minnetonka, Minnesota
William C. Ballard, Jr.	Of Counsel of Greenbaum Doll & McDonald PLLC	9900 Bren Road East Minnetonka, Minnesota
Stephen J. Hemsley	President and Chief Executive Officer of UNH	9900 Bren Road East Minnetonka, Minnesota
James A. Johnson	Vice Chairman of Perseus, LLC	9900 Bren Road East Minnetonka, Minnesota
Thomas H. Kean	Director of UNH	9900 Bren Road East Minnetonka, Minnesota
Douglas W. Leatherdale	Director of UNH	9900 Bren Road East Minnetonka, Minnesota
Mary O. Mundinger, DrPH	Dean of School of Nursing, and Centennial Professor in Health Policy, and Associate Dean of Faculty of Medicine, Columbia University	9900 Bren Road East Minnetonka, Minnesota
Robert L. Ryan	Director of UNH	9900 Bren Road East Minnetonka, Minnesota
Donna E. Shalala, PhD	President, University of Miami	9900 Bren Road East Minnetonka, Minnesota
Gail R. Wilensky, PhD	Senior Fellow, Project HOPE	9900 Bren Road East Minnetonka, Minnesota

EXECUTIVE OFFICERS OF UNH	PRESENT EMPLOYMENT	ADDRESS
Stephen J. Hemsley	President and Chief Executive Officer	9900 Bren Road East Minnetonka, Minnesota
G. Mike Mikan	Executive Vice President and Chief Financial Officer	9900 Bren Road East Minnetonka, Minnesota
Richard H. Anderson	Executive Vice President of UNH and President of Commercial Services Group	9900 Bren Road East Minnetonka, Minnesota
Forrest G. Burke	Acting General Counsel	9900 Bren Road East Minnetonka, Minnesota
Lois E. Quam	Executive Vice President of UNH and President of Public and Senior Markets Group	9900 Bren Road East Minnetonka, Minnesota
Eric S. Rangen	Senior Vice President and Chief Accounting Officer	9900 Bren Road East Minnetonka, Minnesota
David S. Wichmann	Executive Vice President of UNH and President of Individual and Employer Markets Group	9900 Bren Road East Minnetonka, Minnesota

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EX-99.2

EXHIBIT 2

EXECUTION COPY

VOTING AND SUPPORT AGREEMENT

VOTING AND SUPPORT AGREEMENT, dated as of March 11, 2007 (this “Agreement”), by and between UnitedHealth Group Incorporated, a Minnesota corporation (“Parent”), and Anthony M. Marlon, solely in his individual capacity as beneficial owner of common stock of Sierra Health Services, Inc., a Nevada corporation (the “Stockholder”). Capitalized terms used but not defined herein shall have the meanings given to such terms in the Merger Agreement (as defined below).

W I T N E S S E T H:

WHEREAS, Sierra Health Services, Inc., a Nevada corporation (the “Company”) and Parent are, concurrently with the execution and delivery of this Agreement, entering into an Agreement and Plan of Merger, dated as of the date hereof (the “Merger Agreement”), pursuant to which a subsidiary of Parent will merge with and into the Company (the “Merger”); and

WHEREAS, as of the date hereof, the Stockholder is the beneficial owner (as defined under Rule 13d-3 of the Exchange Act) of the shares of the Company’s common stock listed on the signature page hereto (the “Existing Shares” and, together with any shares of the Company’s common stock and options to purchase shares or other voting capital stock of the Company acquired by the Stockholder after the date hereof, the “Shares” but excluding any shares of the Company’s common stock as to which the Stockholder acts in a fiduciary capacity on behalf of persons other than members of his immediate family);

NOW, THEREFORE, in consideration of the foregoing and the mutual representations, warranties, covenants and agreements contained herein, and intending to be legally bound hereby, the parties hereto hereby agree as follows:

ARTICLE I

VOTING

1.1 Agreement to Vote. The Stockholder agrees that, from and after the date hereof and until the date on which this Agreement is terminated pursuant to Section 4.1, at the Company Stockholders Meeting or any other meeting of the stockholders of the Company, however called, or in connection with any written consent of the stockholders of the Company, relating to any proposed action by the stockholders of the Company with respect to the matters set forth in Section 1.1(b) below, the Stockholder shall:

(a) appear at each such meeting or otherwise cause the Shares owned beneficially or of record by the Stockholder to be counted as present thereat for purposes of calculating a quorum; and

(b) vote (or cause to be voted), in person or by proxy, or deliver a written consent (or cause a consent to be delivered) covering, all of the Shares owned by the Stockholder, and any other voting securities of the Company (whenever acquired), that are owned beneficially or of record by the Stockholder or as to which he has, directly or indirectly, the right to vote or direct the voting, (i) in favor of adoption of the Merger Agreement and any other action of the Company’s stockholders requested in furtherance thereof; (ii) against any action or agreement submitted for approval of the stockholders of the Company that would reasonably be expected to result in a material breach of any covenant, representation or warranty or any other obligation or agreement of (A) the Company contained in the Merger Agreement that is reasonably likely to result in any of the conditions to Parent’s or Merger Sub’s obligations under the Merger Agreement not being fulfilled and (B) the Stockholder contained in this Agreement; and (iii) against any Company Takeover Proposal or any other action, agreement or transaction submitted for approval to the stockholders of the Company that the Stockholder would reasonably expect is intended, or would reasonably be expected, to materially impede, interfere with, delay, postpone, discourage or adversely affect the Merger or this Agreement; provided, however, that the parties acknowledge that (x) this Agreement is entered into by the Stockholder solely in his capacity as beneficial owner of the Shares, (y) the Stockholder shall not be deemed to make any agreement or understanding in this Agreement in his capacity as a director or officer of the Company and (z) nothing in this Agreement, including without limitation Section 3.1(d), shall limit or affect any actions taken by the Stockholder in his capacity as a director or officer of the Company or shall prevent the Stockholder from discharging his fiduciary duties as director or officer of the Company or any other fiduciary duties owed by the Stockholder to persons other than members of his immediate family.

Notwithstanding anything to the contrary herein, (1) in the event that the vote of the Shares is required in order to effect an amendment to the Merger Agreement, the provisions of this Agreement, including this Section 1.1, will not apply with respect to the Stockholder’s vote of the Shares and (2) nothing in this Agreement shall be deemed to require the Stockholder to exercise any options to acquire shares of the Company’s common stock or to make any other change in the form of the Stockholder’s ownership of the Shares.

1.2 No Inconsistent Agreements. The Stockholder hereby covenants and agrees that, except for actions taken in furtherance of this Agreement, the Stockholder (a) shall not enter into at any time while this Agreement remains in effect, any voting agreement or voting trust with respect to the Shares owned beneficially or of record by the Stockholder and (b) shall not grant at any time while this Agreement remains in effect, a proxy, a consent or power of attorney with respect to the Shares

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owned beneficially or of record by the Stockholder, in the case of clauses (a) and (b) which would be inconsistent with or violative of Section 1.1.

1.3 Proxy. The Stockholder hereby grants to Parent a proxy to vote the Shares owned beneficially and of record by the Stockholder in the manner indicated in Section 1.1 above (which proxy shall be limited to the matters set forth in Section 1.1). The Stockholder intends that such proxy will be irrevocable (pursuant to Section 78.355(5) of the Nevada Revised Statutes) and coupled with an interest and the Stockholder will take such further action or execute such other instruments as may be necessary to effectuate the intent of this proxy. Such proxy continues in force until it expires automatically and without further action by the parties upon termination of this Agreement. With respect to any meeting of the stockholders of the Company (including the Company Stockholders Meeting), if Parent does not attend such meeting, the Stockholder may exercise his powers as stockholder at such meeting and the vote of the Stockholder may be regarded by the Company when the votes with respect to such meeting are counted; provided, however, the Stockholder shall act in accordance with Section 1.1 hereto.

ARTICLE II

REPRESENTATIONS AND WARRANTIES

2.1 Representations and Warranties of the Stockholder. The Stockholder hereby represents and warrants to Parent as follows:

(a) Authorization; Validity of Agreement; Necessary Action. This Agreement has been duly executed and delivered by the Stockholder and, assuming this Agreement constitutes a valid and binding obligation of Parent, constitutes a valid and binding obligation of the Stockholder, enforceable against the Stockholder in accordance with its terms (subject to applicable bankruptcy, solvency, fraudulent transfer, reorganization, moratorium and other Laws affecting creditors’ rights generally from time to time in effect and to general principles of equity).

(b) Ownership. As of the date hereof, the number of shares of the Company’s common stock beneficially owned (as defined under Rule 13d-3 of the Exchange Act) by the Stockholder is listed on the signature page hereof. The Existing Shares listed on the signature page hereof are, and (except as otherwise permitted by this Agreement) any additional shares of the Company’s common stock and any additional shares subject to vested options to purchase shares of the Company’s common stock acquired by the Stockholder after the date hereof and prior to the Effective Time will be, owned beneficially by the Stockholder. As of the date hereof, the Existing Shares listed on the signature page hereof constitute all of the shares of the Company’s common stock held of record, beneficially owned by or for which voting power or disposition power is held or shared by the Stockholder in a capacity other than as a fiduciary with respect to persons other than members of his immediate family. Except for the limitations stated on

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the signature page to this Agreement, the Stockholder has and (except as otherwise permitted by this Agreement) will have at all times through the Effective Time sufficient rights and powers over the voting and disposition with respect to the matters set forth in Article I or Section 3.1 hereof, and to agree to all of the matters set forth in this Agreement, in each case with respect to all of the Existing Shares and with respect to all of the Shares at the Effective Time, with no other limitations, qualifications or restrictions on such rights, subject to applicable federal securities laws and the terms of this Agreement; provided, however, that the Shares that have been deposited in brokerage accounts may be subject to standard share lending terms, as to which Stockholder will use his reasonable best efforts to ensure that such Shares as may have been loaned will be returned to his control promptly following execution of this Agreement and will not thereafter be loaned to third parties for so long as this Agreement remains in effect. The Stockholder has good title to the Existing Shares listed on the signature page hereof, free and clear of any Liens and (except as otherwise permitted by this Agreement and subject to the terms of any applicable account agreement with a brokerage firm, including any such agreement relating to a margin account), the Stockholder will have good title to such Existing Shares and any additional shares of the Company’s common stock and options to purchase shares of the Company’s common stock acquired by the Stockholder after the date hereof and prior to the Effective Time, free and clear of any Liens.

(c) No Violation. The execution and delivery of this Agreement by the Stockholder does not, and the performance by the Stockholder of his obligations under this Agreement will not, (i) to his knowledge, conflict with or violate any law, ordinance or regulation of any Governmental Authority applicable to the Stockholder or by which any of his assets or properties is bound or (ii) conflict with, result in any breach of or constitute a default (or an event that with notice or lapse of time or both would become a default) under, or give to others any rights of termination, acceleration or cancellation of, or require payment under, or result in the creation of any Liens on the properties or assets of the Stockholder pursuant to, any Contract to which the Stockholder is a party or by which the Stockholder or any of his assets or properties is bound, except for any of the foregoing as would not reasonably be expected, either individually or in the aggregate, to prevent the Stockholder from performing his obligations hereunder.

ARTICLE III

OTHER COVENANTS

3.1 Further Agreements of Stockholder. (a) The Stockholder hereby agrees, while this Agreement is in effect, and except as expressly contemplated hereby, not to sell, transfer, pledge, encumber, assign, distribute, gift or otherwise dispose of (each, a “Transfer”) or enter into any contract, option or other arrangement or understanding with respect to any Transfer (whether by actual disposition or effective economic disposition due to hedging, cash settlement or otherwise) of, any of the Existing Shares, any additional shares of the Company’s common stock and options to purchase shares of the Company’s common stock acquired beneficially or of record by

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the Stockholder after the date hereof, or any interest therein; provided that nothing contained in this Agreement shall restrict the Stockholder from making Transfers to effect estate planning and gifts so long as the transferee in such Transfer shall execute an agreement to be bound by the terms of this Agreement and such Transfer shall not result in the incurrence of any Lien upon any Shares.

(b) In case of a stock dividend or distribution, or any change in the Company’s common stock by reason of any stock dividend or distribution, split-up, recapitalization, combination, exchange of shares or the like, the term “Shares” shall be deemed to refer to and include the Shares as well as all such stock dividends and distributions and any securities into which or for which any or all of the Shares may be changed or exchanged or that are received in such transaction.

(c) The Stockholder agrees, while this Agreement is in effect, to notify Parent promptly in writing of (i) the number of any additional shares of the Company’s common stock, any additional options to purchase shares of the Company’s common stock or other securities of the Company acquired by the Stockholder, if any, after the date hereof and (ii) with respect to the subject matter contemplated by Section 3.1(d), any such inquiries or proposals that are received by, any such information that is requested from, or any such negotiations or discussions that are sought to be initiated or continued with, the Stockholder (in each case, solely in its capacity as a stockholder of the Company).

(d) The Stockholder agrees solely in its capacity as a stockholder of the Company, while this Agreement is in effect, not to, nor to permit any investment banker, financial adviser, attorney, accountant or other representative or agent of the Stockholder to, directly or indirectly, (i) solicit, initiate, cause, knowingly encourage or knowingly facilitate, any inquiries or the making of any proposal or offer to acquire the Shares or (ii) participate in any discussions or negotiations, or furnish to any person any information in connection with or in furtherance of, any proposal to acquire the Shares; provided, however, that the Stockholder may (x) furnish information with respect to the Company and its Subsidiaries to the person making such Company Takeover Proposal (and its Representatives) if at such time the Company is permitted to do so pursuant to the Merger Agreement and (y) participate in discussions or negotiations with the person making such Company Takeover Proposal (and its Representatives) regarding such Company Takeover Proposal if at such time the Company is permitted to engage in, and is actually engaged in, discussions or negotiations with such person regarding such a Company Takeover Proposal.

(e) The Stockholder agrees, while this Agreement is in effect, not to take, agree or commit to take any action that would be reasonably likely to (or fail to take any action where such failure to act would be reasonably likely to) make any representation and warranty of the Stockholder contained in this Agreement inaccurate in any material respect as of any time during the term of this Agreement.

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ARTICLE IV

MISCELLANEOUS

4.1 Termination. This Agreement shall terminate automatically, without any action on the part of any party hereto, upon the earlier to occur of (a) the Effective Time and (b) the date and time of termination of the Merger Agreement by either or both of Parent and the Company pursuant to Section 8.1 of the Merger Agreement. Upon such termination, no party shall have any further obligations or liabilities hereunder; provided, however, such termination shall not relieve any party from liability for any willful breach of this Agreement prior to such termination.

4.2 Further Assurances. From time to time, at the other party’s request and without further consideration, each party shall execute and deliver such additional documents and take all such further action as may be reasonably necessary or desirable to consummate the transactions contemplated by this Agreement.

4.3 No Ownership Interest. Nothing contained in this Agreement shall be deemed to vest in Parent any direct or indirect ownership or incidence of ownership of or with respect to any Shares. All rights, ownership and economic benefits of and relating to the Shares shall remain vested in and belong to the Stockholder, and Parent shall have no authority to manage, direct, superintend, restrict, regulate, govern or administer any of the policies or operations of the Company or exercise any power or authority to direct the Stockholder in the voting of any of the Shares, except as otherwise provided herein.

4.4 Notices. All notices and other communications hereunder shall be in writing and shall be deemed given if delivered personally, telecopied (with confirmation) or delivered by an overnight courier (with confirmation) to the parties at the following addresses (or at such other address for a party as shall be specified by like notice):

(a) if to Parent to:

UnitedHealth Group Incorporated

UnitedHealth Group Center

9900 Bren Road East

Minnetonka, Minnesota 55343

Facsimile No.: (952) 936-0044

Attention: General Counsel

with a copy to:

Sullivan & Cromwell LLP

125 Broad Street

New York, New York 10004

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Fax: (212) 558-3588

Attention: Keith A. Pagnani

(b) if to the Stockholder to the address listed next to his name on the signature page hereto.

Any party may change the address to which notices and other communications hereunder are to be delivered by giving the other parties notice in the manner set forth herein.

4.5 Interpretation. When a reference is made in this Agreement to an Article, a Section, Exhibit or Schedule, such reference shall be to an Article of, a Section of, or an Exhibit or Schedule to, this Agreement unless otherwise indicated. The words “hereof,” “herein” and “hereunder” and words of similar import when used in this Agreement shall refer to this Agreement as a whole and not to any particular provision of this Agreement, and section references are to this Agreement unless otherwise specified. Whenever the words “include,” “includes” or “including” are used in this Agreement, they shall be deemed to be followed by the words “without limitation.” The headings contained in this Agreement are for reference purposes only and shall not affect in any way the meaning or interpretation of this Agreement. Any agreement, instrument or statute defined or referred to herein or in any agreement or instrument that is referred to therein means such agreement, instrument or statute as in effect on the date hereof.

4.6 Counterparts. This Agreement may be executed in one or more counterparts, all of which shall be considered one and the same agreement and shall become effective when one or more counterparts have been signed by each of the parties and delivered to the other party. Facsimile or other electronic transmission of any signed original document and/or retransmission of any signed facsimile or other electronic transmission will be deemed the same as delivery of an original

4.7 Entire Agreement. This Agreement (together with the Merger Agreement, to the extent referred to herein) constitutes the entire agreement and supersedes all prior agreements and understandings, both written and oral, between the parties with respect to the subject matter hereof.

4.8 Governing Law. This Agreement shall be governed by, and construed in accordance with, the Laws of the State of Nevada, regardless of the Laws that might otherwise govern under applicable principles of conflicts of laws thereof.

4.9 Amendment. This Agreement may not be amended except by an instrument in writing signed on behalf of each of the parties hereto.

4.10 Enforcement. The parties agree that irreparable damage would occur and that the parties would not have any adequate remedy at law in the event that any of the provisions of this Agreement were not performed in accordance with their specific terms or were otherwise breached. It is accordingly agreed that the parties shall be entitled to an injunction or injunctions to prevent breaches of this Agreement and to

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enforce specifically the terms and provisions of this Agreement in the United States District Court for the District of Nevada or any state court in the State of Nevada, this being in addition to any other remedy to which they are entitled at law or in equity.

4.11 Severability. If any term or other provision of this Agreement is invalid, illegal or incapable of being enforced by any rule of law or public policy, all other conditions and provisions of this Agreement shall nevertheless remain in full force and effect. Upon such determination that any term or other provision is invalid, illegal or incapable of being enforced, the parties hereto shall negotiate in good faith to modify this Agreement so as to effect the original intent of the parties as closely as possible to the fullest extent permitted by applicable Law in an acceptable manner to the end that the transactions contemplated hereby are fulfilled to the extent possible.

4.12 Assignment; Third Party Beneficiaries. Neither this Agreement nor any of the rights, interests or obligations hereunder shall be assigned, in whole or in part, by operation of Law or otherwise by any of the parties without the prior written consent of the other parties and any attempt to make any such assignment without such consent shall be null and void. Subject to the preceding sentence, this Agreement will be binding upon, inure to the benefit of, and be enforceable by, the parties and their respective successors and assigns. This Agreement is not intended to confer upon any person other than the parties hereto any rights, benefits or remedies.

[Signatures appear on following pages.]

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IN WITNESS WHEREOF, the parties hereto have signed or have caused this Agreement to be signed by their respective officers or other authorized persons thereunto duly authorized as of the date first written above.

UNITEDHEALTH GROUP INCORPORATED
By:	Stephen J. Hemsley
	Name: Stephen J. Hemsley Title: President and Chief Executive Officer

Signature Page to Voting and Support Agreement

VOTING AND SUPPORT AGREEMENT

Counterpart Signature Page

IN WITNESS WHEREOF, the Stockholder has executed this Agreement as of the date first written above. The next subsequent page of this Agreement, which contains details of the number of Shares owned beneficially and of record by the Stockholder and the Stockholder’s address for notices, is hereby incorporated in this signature page by reference.

/s/ Anthony M. Marlon                  

Anthony M. Marlon, individually

Signature Page to Voting and Support Agreement

Existing Shares Beneficially Owned by Stockholder:

Directly:                                 -0-

Indirectly:	(i)	3,826,954 shares held indirectly through a total of four trusts established by Stockholder and his wife;
	(ii)	3,000 shares held indirectly through a limited partnership (the “Partnership”);
	(iii)	305,296 shares held indirectly by the AMM&RM Family Limited Partnership “ARFLP”); and
	(iv)	212,830 shares held for Stockholder’s account under the Company’s 401(k) plan for employees, as to which Stockholder has dispositive power but as to which his right to vote is not explicitly provided in plan and plan trust documents.
Shares subject to rights to acquire:		24,000 options exercisable currently

Stockholder may be deemed to have or share voting power and/or dispositive power over the shares held by the four trusts and, therefore, to have beneficial ownership with respect to such shares. Stockholder, as managing general partner of the Partnership, has sole voting and dispositive power over the shares held by the Partnership. Stockholder, as a general partner of ARFLP, may be deemed to have or share voting and/or dispositive power over the shares held by ARFLP (a limited partnership of which Stockholder, his spouse, and a trust for the benefit of Stockholder’s adult daughter, are general and/or limited partners). In past filings with the Securities and Exchange Commission, Stockholder has disclaimed beneficial ownership as to the shares held by the four trusts, other than the 1,439,630 shares held by the Marlon Family Trust (a revocable trust of which he is a trustee), and the shares held by ARFLP.

        Address for notices:         Anthony M. Marlon c/o Sierra Health Services, Inc. 2724 North Tenaya Way Las Vegas, Nevada 89128 Facsimile No.: (702) 242-1532   with a copy to:   Morgan, Lewis & Bockius LLP 101 Park Avenue New York, New York 10178 Facsimile No.: (212) 309-6001 Attention: Stephen P. Farrell, Howard L. Shecter and R. Alec Dawson

The following persons, which have or may have rights with respect to Existing Shares or Shares beneficially owned by the Stockholder, hereby agree and consent to the terms of this Agreement insofar as they affect the rights of the undersigned:

AMM&RM FAMILY LIMITED PARTNERSHIP
By:	/s/ Anthony M. Marlon, M.D.
	Name: Anthony M. Marlon, M.D. Title: General Partner and Limited Partner

AMM&RM FAMILY PARTNERS, LTD.
By:	/s/ Renee Marlon
	Name: Renee Marlon Title: General Partner and Limited Partner

MARLON FAMILY TRUST DATED OCTOBER 23, 1985

/s/ Anthony M. Marlon, M.D.
Name:	Anthony M. Marlon, M.D.
Title:	Trustee

/s/ Renee Marlon
Name:	Renee Marlon
Title:	Trustee

ANTHONY M. MARLON CHARITABLE REMAINDER TRUST DATED APRIL 7, 1993

/s/ Anthony M. Marlon, M.D.
Name:	Anthony M. Marlon, M.D.
Title:	Trustee

/s/ Erin E. MacDonald
Name:	Erin E. MacDonald
Title:	Trustee

RENEE MARLON CHARITABLE REMAINDER TRUST DATED APRIL 7, 1993

By:	/s/ Anthony M. Marlon, M.D.
	Name: Anthony M. Marlon, M.D. Title: Trustee

By:	/s/ Erin E. MacDonald
	Name: Erin E. MacDonald Title: Trustee

AMRM FAMILY TRUST DATED AUGUST 11, 1993

By:	/s/ Erin E. MacDonald
	Name: Erin E. MacDonald Title: Trustee

By:	/s/ William R. Godfrey
	Name: William R. Godfrey Title: Trustee

EX-99.4

EXHIBIT 4

CERTAIN INFORMATION REGARDING THE STOCKHOLDER

The information disclosed in this Exhibit 4 relating to the Stockholder is based on information contained in the Proxy Statement on Schedule 14A filed by the Company on April 13, 2006.

The following table sets forth the name and present principal occupation or employment, and the name and principal business address of any corporation or other organization in which such occupation or employment is conduct. The business address of the Stockholder is 2724 North Tenaya Way, Nevada 89128. The Stockholder is a citizen of the United States.

STOCKHOLDER	PRESENT PRINCIPAL OCCUPATION
Anthony M. Marlon, M.D.	Chief Executive Officer/President and Director, Sierra Health Services, Inc.

To the best of UNH’s knowledge, the Stockholder has not during the last five years (a) been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors), or (b) been a party to any civil proceeding of a judicial or administrative body of competent jurisdiction as a result of which such person was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, Federal or State securities laws or finding any violation with respect to such laws.