Prospective payment has created incentives for hospitals to identify physicians who are responsible for high or excessive rates of resource use. However, at teaching hospitals it is unclear whether individual attending or resident physicians account for a substantial portion of the observed variations in hospital resource use. To explore this issue, case-mix adjusted hospital length of stay and ancillary resource use at a university teaching hospital for 7,667 consecutive discharges on general medicine wards and 7,566 discharges on medical subspecialty wards were evaluated. After controlling for case mix and patient characteristics (patients' age, sex, marital status, insurance status, and ward service), only 2% of the length of stay variance (log transformed) was attributable to the attending physician on general medicine wards (p = 0.06) and 1% on subspecialty medicine wards (p <0.01). For total ancillary resource use, about 2% of the variance was attributable to general medicine and subspecialty ward attendings. Similar associations were found for resident physicians, although the overlap of attending and resident physicians' month-long rotations prevented critical appraisal of their independent contributions to resource use. Furthermore, labeling attending physicians as high or low hospital resource utilizers based on data from one month of attending duty (mean admissions = 33±7) would be scarcely better than randomly classifying them (kappas ranged from -0.05 for length of stay on subspecialty services to 0.18 for pharmacy use on general medicine services). In conclusion, in this university teaching hospital, attendings and residents account for a small, although statistically significant, amount of the variation in hospital resource use. It would be impractical for the hospital to reliably profile the resource use intensity of individual physicians.