This is a report of pulmonary actinomycosis which has been treated with long chemotherapy under the misdiagnosis of pulmonary tuberculosis for 14 years and has finally diagnosed by the specimens of excised lung. Pulmonary actinomycosis is very few in recent report by the use of penicillin and sulfonamide, but for the difficult differential diagnosis with pulmonary tuberculosis and carcinoma, It is a choice of treatment for resect for the localized lesions.[KTCS 1973;1:23-28]