The clinical features of tracheobronchial tuberculosis are distinct from those of pulmonary tuberculosis in some aspects. Streptomycin (SM) is claimed by some investigators that it has a tendency to promote the development of bronchial stenosis due to scarred healing of the involved endobronchial mucosa, and, for that reason, they recommend not to use it in treatment of bronchial tuberculosis. In some patients with pulmonary tuberculosis, who have renal or hearing disturbance, SM avoided. Yet unless SM is used improvement of tuberculosis could be delayed. It is the purpose of the present investigation to point out that aerosol therapy of SM is useful for patients with respiratory tuberculosis. Furthermore, we wish to demonstrate that we can safely treat the patients with respiratory tuberculosis who suffer from renal function or hearing disorder by use of aerosol therapy of SM. Prior to clinical application of the inhalation therapy, we confirmed that the therapy was not harmful. Serum concentration of SM, when inhaled, was measured in 9 volunteers. Before and after administration of SM aerosol, spirograms were examined in 4 volunteers, nevertheless, no special abnormality was recognized. It seemed that serum concentration of SM after the administration was two low to evoke adverse reactions (less than 3.0 gamma). In 6 patients with pulmonary tuberculosis, blood gases were measured and no obvious change was observed. As a result, it was demonstrated that the endobronchial tuberculous lesions improved faster when treated by inhalation of aerosolized SM as compared with the conventional injection therapy, without evoking any apparent adverse reactions. In some of the patients with pulmonary tuberculosis, it seemed that the therapy was useful.(ABSTRACT TRUNCATED AT 250 WORDS)