Therapeutic results of Cs¹³⁷ for malignant tumors in 105 patients, who visited the E.N.T. clinic of this hospital from July 1962 to August 1963, have been investigated. The results are as follows. 1) Male patients (85 cases) were four times as many as the female (20 cases). 2) Most patients (80%) were distributed between the fourtieth and sixtieth decades of age. 3) A large proportion of them (70%) visited this clinic for the first time 3 to 12 months following their subjective onsets of the disease. 4) Laryngeal tumors comprised the highest incidence (26%) followed in order by the tumors of maxillary sinus (15%), tongue (10%), and those of palate (8%). 5) Histopathologically, the tumors were carcinomas (80 cases), sarcomas (13 cases), and other malignant tumors (12 cases). 6) They were classified according to the degree of progression as follows : Third degree (63 cases), second degree (23 cases), fourth degree (15 cases), and first degree (4 cases). 7) Therapeutic results of Cs¹³⁷ in full dosage among 57 patients were good in 12 patients, fair in 39, palliative in 4, and negative in 2.