Exhibit 24.1

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Thomas L. Strickland, Christopher J. Walsh and Dannette L. Smith, and each of them, his/her true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution, to sign, execute and file with the Securities and Exchange Commission (or any other governmental or regulatory authority), for us and in our names in the capacities indicated below, a registration statement on Form S-3 (including all amendments thereto) with all exhibits and any and all documents required to be filed with respect thereto, granting unto said attorneys-in-fact and agents and each of them, full power and authority to do and to perform each and every act and thing necessary or desirable to be done in and about the premises in order to effectuate the same as fully to all intents and purposes as he himself/she herself might or could do if personally present, hereby ratifying and confirming all that said attorneys-in-fact and agents, or any of them, may lawfully do or cause to be done by virtue hereof.

/s/    STEPHEN J. HEMSLEY

Stephen J. Hemsley

Director, President and Chief Executive Officer

(principal executive officer)

Dated: January 31, 2008

/s/    GEORGE L. MIKAN III

George L. Mikan III

Executive Vice President and Chief Financial Officer

(principal financial officer)

Dated: January 31, 2008

/s/    ERIC S. RANGEN

Eric S. Rangen

Senior Vice President and Chief Accounting Officer

(principal accounting officer)

Dated: January 31, 2008

/s/    WILLIAM C. BALLARD, JR.

William C. Ballard, Jr.

Director

Dated: January 31, 2008

/s/    RICHARD T. BURKE

Richard T. Burke

Director

Dated: January 31, 2008

/s/    ROBERT J. DARRETTA

Robert J. Darretta

Director

Dated: January 31, 2008

/s/    MICHELE J. HOOPER

Michele J. Hooper

Director

Dated: January 31, 2008

/s/    James A. Johnson

James A. Johnson

Director

Dated: January 31, 2008

/s/    THOMAS H. KEAN

Thomas H. Kean

Director

Dated: January 18, 2008

/s/    DOUGLAS W. LEATHERDALE

Douglas W. Leatherdale

Director

Dated: January 31, 2008

/s/    MARY O. MUNDINGER, DR. P.H.

Mary O. Mundinger, Dr. P.H.

Director

Dated: January 22, 2008

/s/    ROBERT L. RYAN

Robert L. Ryan

Director

Dated: January 31, 2008

/s/    GAIL R. WILENSKY, PH.D.

Gail R. Wilensky, Ph.D.

Director

Dated: January 31, 2008