The rate of the compromised host tend to increase in the pulmonary tuberculosis due to long term use of immunosuppressive drugs, such as anti-cancer drugs and corticosteroids. On the one hand, the incidence of tuberculosis has reduced in Japan, so, many doctors consider tuberculosis as a disease of the past, and doctor's delay is the serious problem. We investigated pulmonary tuberculosis in the compromised host. 1) Chiba University Hospital. For five years, the 77 cases were diagnosed as pulmonary tuberculosis, for their sputum examination were positive. The 54 cases didn't have other diseases, the 17 cases had various type of cancer, and only one case was administrated with corticosteroid. 2) National Chiba-Higashi Hospital. For 6 years, the 82 cases had various type of cancer and the 21 cases were administrated with corticosteroids, in the 1954 cases of pulmonary tuberculosis patients in our hospital. In the cases having cancer, the 18 cases had lung cancer, the 36 cases had cancer of the digestive organs. In the cases of having lung cancer, the 12 cases died of cancer and no cases died of pulmonary tuberculosis. In the cases of having cancer of the digestive organs, the 17 cases died of cancer and the 3 cases died of pulmonary tuberculosis. In the cases administrated with corticosteroids, the 17 cases had been treated for collagen disease. In these cases, many patients were progressive state on chest roentogenograms. When their onset of pulmonary tuberculosis, the 12 cases were administrated with low dose of corticosteroids. In all cases, chemoprophylaxis had not been done.(ABSTRACT TRUNCATED AT 250 WORDS)