The present study examined certain medical and social aspects of TB based on analysis of 630 cases selected from 1,480 patients having chronic pulmonary TB in Finland, in 1964. The findings of the studies were: Median age of the patients was 50.2 years for men and 45.2 years for women; the duration of roentgenologic history of TB was an average of 12.3 years and of the bacteriologic history, 10.1 years. About 15% of close contacts (family members) developed TB during the patients' illness. Resistance to M. TB was found among 80% of the cases examined for it. The disease was far advanced in 50% of the cases. Only 18% of the patients had no other diseases and the most common concurrent afflictions were vascular and psychiatric diseases. Two-thirds of the patients came from the two lowest social classes. In a fairly large number of cases, neglect of earlier therapy was encountered in the data. A comparison of data from the present study with the corresponding situation in Helsinki at the beginning of 1961 (which comprised of patients with positive sputa findings for a minimum of two years) showed that the age and sex distribution in both studies and the occurrence of resistance to first-line drugs were almost identical. It was concluded that at least half of the chronic pulmonary tuberculotics could be treated to bacilli-free state and that chronic cases could only be treated from the epidemiological point of view. When the age structure, disability due to the lungs being affected, psychic and additional somatic diseases were considered, little success could be expected from rehabilitating the patients for productive work.