Clinical investigative studies of the ototoxic effects of streptomycin are presented on 198 cases of admission at Masan National Hospital for treatment of pulmonary tuberculosis. The results were as follows : 1. General ototoxic complications such as vertigo, tinnitus and hearing disturbance were occurred in 59 cases (29.8%). Of 198 cases, 33.8% manifested vestibular damage and 15.2% manifested cochlear damage. 2. The hearing loss by streptomycin sulfate chiefly in high frequency range, occurred relatively higher incidence but hearing loss in the middle and low frequency range was relatively lower. 3. There is no relationship between incidence of streptomycin deafness and dosage of streptomycin administered. 4. There is close relationship between streptomycin deafness and age, higher incidence in order to increase age. 5. The cases who received 1.0gm streptomycin daily resulted in more frequent incidence of hearing disturbance (17.4%) than that (2.9%) of 1.0gm single dose, twice a week. 6. Abrupt descending type of audiogram is 48%, and horizontal type is 30.0%. 7. In general, a definite relation exist between the severity of deafness and greater dosage of streptomycin administered.