Medicare is the government program that insures many of the nation’s retirees and Americans with disabilities. Coverage for prescription medicines filled at a pharmacy first became available in 2006 under the Medicare Part D program. Private health plans administer the program and compete for beneficiary enrollment. These plans also negotiate with manufacturers, without government interference, to secure to secure savings on medicines. This market-based approach has been successful since the program’s beginning, but some in Washington now are considering fundamental change.