OBJECTIVE: Although overuse of antibiotics in children has been well documented, relatively little information is known about provider and facility characteristics associated with this prescribing practice. This study was done to evaluate the differences in overuse of antibiotics among staff physicians and resident/interns (housestaff [HS]) who work in hospital-based outpatient clinics. METHODS: This cross-sectional study involved patient encounters in outpatient departments that were included in the US National Hospital Ambulatory Medical Care Survey database from 1995 to 2000. Encounters with patients who were aged <18 years and had a primary diagnosis suggestive of viral respiratory tract infection were evaluated. Patients with comorbid conditions that might justify antibiotic use were excluded. RESULTS: This study included 1952 patient encounters with a primary diagnosis suggestive of a viral infection and 33.2% of these patients receiving antibiotics. Overall, antibiotic use was significantly less among HS (19.5%) than staff physicians (36.4%; odds ratio [OR]: 0.44; 95% confidence interval [CI]: 0.33-0.59). This difference between HS (19.5%) and staff physicians (32.5%) persisted even within teaching hospitals (OR: 0.5; 95% CI: 0.4-0.7). Among staff physicians, antibiotic use was greater among those who work in nonteaching (39.6%) compared with teaching hospitals (32.5%; OR: 1.51; 95%: CI 1.15-1.98). Controlling for other patient and provider variables, antibiotic use occurred less among HS than among staff physicians in teaching hospitals (OR: 0.53; 95% CI: 0.38-0.75). CONCLUSIONS: Antibiotic prescribing in the context of an outpatient visit for a diagnosis suggestive of a viral respiratory tract illness occurs more commonly among staff physicians than trainees and among staff physicians more commonly in nonteaching compared with teaching institutions.