Under the Medicare program the Dept. of Health & Human Services (HHS) & its contractors paid a reported $330 billion in Medicare benefits in 2005. This testimony addresses Medicare physicians, health professionals, & suppliers for services related to senior health care, who received about 20% of all Medicare payments. The author was asked to determine if Medicare Part B physicians, health professionals, & suppliers have unpaid fed. taxes, & if so, to: (1) determine the magnitude of such debts; (2) identify examples of Medicare physicians & suppliers that have engaged in abusive or potentially criminal activities; & (3) assess HHS efforts to prevent delinquent taxpayers from enrolling in Medicare & levy payments to pay delinquent fed. taxes. Tables.