A 44-year-old man was admitted to the hospital because of acute promyelocytic leukemia. A nodular shadow (2.5 cm in diameter) was seen in the right upper lung field on a chest roentgenogram. During the administration of combination chemotherapy for the leukemia, diffuse granular shadow appeared in all lung fields. Transbronchial lung biopsy findings indicated tuberculosis. The patient was given streptomycin, isoniazid, rifampicin and ethambutol, but the nodular show enlarged and a pleural effusion appeared on the right side. Cytologic examination of the pleural effusion revealed adenocarcinoma. Similar findings were obtained from a second transbronchial lung biopsy. The frequency of association of lung cancer and other malignancy is about 4%. The incidences of primary lung cancer found during the course of active tuberculosis, active pulmonary tuberculosis found during the course of primary lung cancer, and tuberculosis found during the course of acute leukemia are 0.9 to 1.4%, 0.4 to 4.3%, and 2.4 to 4.5%, respectively. To our knowledge, this is the first case in Japan in which adenocarcinoma of the lung was associated with acute promyelocytic leukemia and tuberculosis.