The incidence of tuberculosis among immigrants to the United States is 12 times that in the native-born population. Screening immigrants for tuberculosis is complicated by the widespread use of bacille Calmette-Guérin (BCG) vaccination. To determine the utility of tuberculin testing in adults who have been vaccinated with BCG vaccine, we studied the tuberculin reactions of 80 adults who came to us for naturalization physical examinations. No adverse effects were reported from tuberculin testing. Subjects from regions with a low prevalence of tuberculosis who had received BCG vaccine were significantly more likely to have a positive reaction than subjects who had not received BCG vaccine. However, among subjects from regions with a high prevalence of tuberculosis, there was no difference in the prevalence of positive reactions between those who reported having BCG vaccinations and those who said they had not. Interpretation of tuberculin reactions in immigrants who receive BCG vaccinations depends on the prevalence of tuberculosis in the country of origin. Adults receiving BCG vaccination who have a positive reaction and no evidence of active tuberculosis should receive prophylactic therapy or be observed carefully.