Following the implementation of Medicare+Choice, many health care plans terminated their contracts & fully withdrew from the program or partially withdrew by reducing the geographic areas they served, & more have announced that they will withdraw for the 2001 contract year. This report (1) determines the geographic distribution & the distribution among plans of enrollees affected by the recent plan withdrawals, (2) identifies the factors associated with plans that terminated or reduced their participation in the program, & (3) examines the likely role of payment rates in affecting plans' decisions. Analyzes enrollment & plan participation data. Tables.