There were declining trends of main epidemiological indices of tuberculosis in Czechoslovakia from 1966 to 1974 (Fig. 1 and 2). The smallest average yearly decrease of 4.9% was in the incidence of newly detected cases of active tuberculosis, the largest one of 21.6% in the prevalence of "tuberculous chronics" excreting tubercle bacilli in the last two years or longer. The total of newly detected cases of active tuberculosis and relapses per 100,000 inhabitants of corresponding groups of sex and age decreased in 1966--1974 in nearly all age groups of both sexes, the highest rates being in persons aged 45 years and over (Fig. 3). The participation of corresponding groups of population in BCG vaccination procedures was very high at the national scale during 1966--1974. The highest relative number of active cases of respiratory tuberculosis newly detected by photofluorography per 100,000 examinees of the appropriate group was found in persons with "fibrotic" lung lesions, less in persons investigated for their symptoms, still less in contacts with tuberculosis cases and least in persons not registered for lung lesions and investigated in mass X-ray examinations. The number of beds in institutions for special care of tuberculosis and respiratory diseases per 1,000 population by the end of the corresponding year decreased in Czechoslovakia from 1.1 in 1966 to 0.8 in 1974. The decrease of rates of tuberculous patients was accompanied by a decrease of the number of cases under ambulatory chemotherapy of tuberculosis. At the same time there was an increase in the number of cases treated for nontuberculous respiratory diseases in out-patients' and in-patients' departments of tuberculosis and respiratory diseases. In spite of the favourable epidemiological development of tuberculosis there remain large groups of the population -- especially in middle and higher age groups -- infected with tuberculosis in the past in which new cases of active tuberculosis may appear.