The diagnosis and differential diagnosis of pulmonary tuberculosis--in spite of its general decline in frequency--remains an important task, even today. There are certain types of opacification which should make one think of TB. A pulmonary nodule--with or without hilar involvement--in an adult may represent primary TB. Postprimary disease is usually located in the first or second lung segment, occasionally also in the sixth. Abnormal findings in the apices are usually tuberculous in origin. Bilateral foci in both upper lobes with similar or identical opacification patterns are especially typical of tuberculosis. Without treatment, there is apico-caudal progression. With tuberculostatic therapy, there usually is rapid regression with relative little scar formation. Residuals of cavities can present as a ring like shadow. Tests for TB-bacteria are usually negative in these cases. Circumscribed older lung lesions in asymptomatic healthy appearing patients mandate supervision of these patients to detect reactivation of the disease, which occurs fairly frequent and to prevent the infection of others.