Clinlcal significances of the anti-lung antibody were studied on the course of the 287 cases of lung tuberuculosis patients. The results summarized as follows; 1. The sera of the patients with various kind of lung diseases were tested for anti-lung-antibody activity against human lung antigen, using the complement fixation reaction. The cases with the positive anti-lung-antibody were in 2 cases out of 4 cases of bronchoectasis, in 2 cases of 4 cases of lung abscess, in 9 cases of thoracic empyema, in 126 cases of 287 cases of lungc tuberuclosis. From the correlation between clinical types (Gakuken's classification in Japan) and antilung antibody the incidence of the positive anti-lung-antibody was as the flloowing ordet. A>B>F>C>D A: Exsudative Form B: Infiltrating-caseous Form C: Fibrose-caseous Form D: Fibrose Form E: Disseminated For F: Serious Mixed Form 2. In the positive anti-lung-antibody cases with lung tuberuculosis the cases with the positive anti-luny-antibody increased in titer gradually and the cases with the continuous or occassional positive anti-lung-antibody for a long period became week and the clinical signs worsened. On the other hand, the cases with the anti-lung-antibody decreased gradually in titer greatly improved. 3. On the course of the lung tuberuculosis circulating antilung-antibody increased in titer in parallel with the increased titer of complete tuberuculin antibody in peripheral blood. 4. After administration of anti-tuberculosis drugs and/or after surgical treatments in the cases with tuberuculosis of the lung the circulating anti-lung-antibody decreased in titer and was not detected in peripheral blood. 5. In the cases with tuberuculoma or lung cavity, the more the capsules of tuberuculoma or the walls of lung cavity were thin, the more the positive anti-lung-antibody cases increased in number, 6. From the distribution of the anti-lung-antibody or complete tuberuculin antibody in the lung of human tuberuculosis, it was found that the amount of complete tuberuculin antibody relatively increased in the focus of tuberuculous lesions supirior to that of anti-lung-antibody, but in the peripheral aroa of the lung tuberuculosis the amount of anti-lung-antibody was detected in higher titer that of complete tuberuculin antibody.