We prospectively evaluated rates of tuberculin skin test (TST) conversion from July 1992 to June 1997 among house staff in the Emory University Affiliated Hospitals Training Program following implementation of expanded infection control measures for tuberculosis at Grady Memorial Hospital (Atlanta), which cares for ∼200 patients with tuberculosis per year. Over 5 years, documented TST conversions occurred for 52 (2.4%) of 2,144 house staff. Conversion rates decreased after the first 6 months from 5.98 to 1.09 per 100 person-years worked over the next 4.5 years (P < .001). Multivariate analysis revealed that risk factors for TST conversion included graduation from a foreign medical school and being part of the house staff in the Department of Medicine; race or ethnicity, gender, and age were not risk factors. Over the last 4.5 years, the TST conversion rate among U.S. medical school graduate house staff (n = 1,928) was 0.72 per 100 person-years worked, and there was no significant difference in conversion rates between house staff in the Department of Medicine and house staff in other departments. In summary, TST seroconversion rates decreased significantly following full implementation of expanded infection control measures for tuberculosis and were low (<1% per year) among U.S. medical school graduates despite their caring for large numbers of patients with tuberculosis at an inner-city public hospital.