The purpose of this study was to assess the effect of Health Care Financing Administration (HCFA) regulations on radiology fellowship training.Surveys were sent to 157 fellowship program directors in body imaging and vascular/interventional radiology. Questions addressed program accreditation status, faculty supervision of fellows, and any change in faculty supervision of fellows in response to HCFA's revised plan for Medicare Part B reimbursement.Eighty of 157 (51%) surveys were returned. Thirty (37%) respondents indicated supervision of fellows had changed after institution of the new HCFA rules in July 1996. Vascular/interventional program directors (n = 25, 49%) were more likely to have changed their practice than body imaging program directors (n = 5, 17%). Nearly all respondents (29 of 30, 97%) indicating a change stated supervision had increased. Twenty-seven (33%) respondents also indicated faculty supervision was beyond that necessary for patient care and house staff education; most of these respondents (21 of 27, 78%) stated the new HCFA regulations were responsible. Many program directors also expressed concern the HCFA regulations might prevent fellows from obtaining sufficient experience to effectively learn independent clinical decision-making.HCFA regulations intended to address attending physician billing practices at teaching institutions may have had the unintended effect of substantively altering the training of radiology fellows.