OBJECTIVE: To determine the prevalence of tuberculous infection among a sample of physicians at Barnes Hospital and to determine the frequency of tuberculin skin testing and the adequacy of follow-up for physicians with positive tuberculin skin tests. DESIGN: Convenience sample. SETTING: 1,000-bed, university-affiliated tertiary care hospital. SUBJECTS: Physicians attending departmental conferences were screened for tuberculosis. Prior history of tuberculosis, antituberculous therapy, BCG vaccination, and previous tuberculin skin test results were obtained with a standardized questionnaire. Tuberculin skin tests were performed on those who were previously skin-test negative. OUTCOME MEASURE: Tuberculosis infection, prophylactic therapy. RESULTS: Eighty-six (24.5%) of 351 physicians in the study were skin test positive by history or currently performed skin test. Of 61 who reported a previously reactive skin test, 40 (66%) had been eligible for isoniazid prophylaxis, but only 15 (37.5%) of 40 had completed at least six months of therapy. Of 290 physicians reporting a previously negative skin test, 25 conversions (8.6%) were identified. Previously undiagnosed, asymptomatic pulmonary tuberculosis was identified in one physician. CONCLUSIONS: Infection with Mycobacterium tuberculosis is common among physicians. Physicians were screened irregularly for tuberculosis, and the use of prophylactic therapy was inconsistent. Aggressive tuberculosis screening programs for healthcare workers should be instituted (Infect Control Hosp Epidemiol 1994;15:95-100).