Growing need for healthcare services. The U.S. Census Bureau estimates that the number of individuals age 65 and older has grown 1.3% compounded annually over the past 20 years and is expected to grow 3.0% compounded annually over the next 20 years, approximately three times faster than the overall population. We believe the anticipated increase in the number of individuals age 65 and older, together with expansion of health coverage, increased prevalence of chronic conditions such as diabetes and advances in technology will drive demand for our specialized medical services and generally favor providers that possess integrated networks and a wide array of services and capabilities

Exhibit 10.91

May 26, 2011

Blackstone Management Partners IV L.L.C.
c/o The Blackstone Group, L.P.
345 Park Avenue
New York, NY 10154

Metalmark Management LLC
c/o Metalmark Capital LLC
1177 Avenue of the Americas
New York, NY 10036

Ladies and Gentlemen:

     Reference is made to that certain Transaction and Monitoring Fee Agreement dated as of September 23, 2004 (the “Agreement”) among Blackstone Management Partners IV L.L.C. (“BMP”), Metalmark Management LLC (“MSCP Manager”, and collectively with BMP, the “Sponsor Management Entities”) and Vanguard Health Systems, Inc. (the “Company”).

     Pursuant to Section 3(a) of the Agreement, the Sponsor Management Entities are entitled to receive additional compensation from the Company for providing investment banking or other financial advisory services to the Company by mutual agreement of the Company and the Sponsor Management Entities. The Company hereby acknowledges that the Sponsor Management Entities at the request of the Company have provided and are providing certain financial advisory services to the Company during its current fiscal year ending June 30, 2011; and, as a result, the Company agrees with the Sponsor Management Entities that, to reflect their contributions to the Company’s accomplishments to date during its current fiscal year, each of BMP and MSCP Manager shall be entitled to financial advisory fees from the Company in consideration of such services in the amounts of $10.0 million and $1.5 million, respectively, such fees payable by June 30, 2011.

     Please execute and return to the Company an executed counterpart of this letter agreement acknowledging your agreement with the foregoing.

Exhibit 10.91

THE FOREGOING IS AGREED AS OF
THE DATE FIRST SET FORTH ABOVE:
BLACKSTONE MANAGEMENT PARTNERS IV L.L.C.
By:		/s/ Michael A. Dal Bello   Michael A. Dal Bello
		Managing Director
Date: May 26, 2011
METALMARK MANAGEMENT LLC
By:		/s/ M. Fazle Husain   M. Fazle Husain
		Managing Director
Date: May 26, 2011