The author reported a patient, aged 32, with many cysts in his left lung. Since he had suffered from fever in suckling age, he caught cold often. bnt was not confined to his bed. A physician diagnosed him as lung tuberculosis on a recent occasion of health examination but intracutaneous tuberculin-reaction and tuberculous bacilli in sputum proved negative. Many cysts of variable sizes with niveau were recognized by means of bronchograph. Wassermann's reaction in serum was positive. By penicillin-therapy his main complaint of thorakalgia and much expectoration was markedly diminished.