To clarify the characteristics of the tuberculosis situation in Japan, it was analysed in comparison with those in other developed countries. The results are summarized as follows: 1. The tuberculosis epidemic peaked at the end of 1910s in Eastern Japan, and in the 1940s in Western Japan. It is estimated that the annual risk of tuberculosis infection was 4% or more until the end of the World War II. Tuberculosis has spread much later and was much more prevalent up through the 1940s in Japan than in other developed countries. 2. A modern tuberculosis control programme including active case-finding, isolation of infectious cases, charge free medication and BCG vaccination was launched in 1951, and in 1961 an effective case-holding system was established. Tuberculosis incidence decreased rapidly thereafter. As the rate of decrease was almost the same as that of the Inuit (Eskimo) (Fig. 1), one might say that Japan is one of the countries where tuberculosis incidence decreased most rapidly. 3. Incidence of tuberculosis in children is 2.1 per 100,000 in 1991 which is lower than that of the U.S.A. (3.1 per 100,000). 4. Incidence of tuberculosis among the aged is much higher than that of other developed countries as shown in Fig. 3. Of course, this is mainly caused by the fact that a higher percentage of Japanese aged 55 years or more was infected with tubercle bacilli in the past.(ABSTRACT TRUNCATED AT 250 WORDS)