This excerpt taken from the UNH 10-K filed Mar 6, 2007.
Key Business Developments
The results of PacifiCare Health Systems, Inc. (PacifiCare), which we acquired in December 2005 for total cash and stock consideration of approximately $8.8 billion, were included for the full year 2006. This acquisition significantly strengthened our resources by enhancing our capabilities on the Pacific Coast and in other Western states and broadening the scope of our product offerings for a host of specialized services.
On January 1, 2006, we began serving as a plan sponsor offering Medicare Part D prescription drug insurance coverage under a contract with the Centers for Medicare & Medicaid Services (CMS). As of December 31, 2006, we had enrolled approximately 5.7 million members in the Part D program, including approximately 4.5 million in the stand-alone prescription drug plans and approximately 1.2 million in Medicare Advantage plans incorporating Part D coverage.