In order to improve the survival rate of patients with clinically inoperable but localized bronchogenic carcinoma, we have developed the following three forms of radiotherapy and analyzed the results in comparison with those obtained by conventional radiotherapy: 1. Irradiation under 95% O2 plus 5% CO2 inhalation, 2. Uneven fractionation irradiation, 3. Intraoperative irradiation. The tumor regression rate was most pronounced in the 95% O2 plus 5% CO2 breathing group and the one-year survival rate was significantly increased. However, the longterm survival rate was almost the same as that of patients treated by conventional radiotherapy. In uneven fractionation irradiation, the follow-up period is short, but the preliminary results seem most encouraging. Intraoperative irradiation is well indicated for patients with poor pulmonary functions, in whom the localized malignant lesions were left behind following excision of the main mass. The reason is that a cancerocidal dose can be delivered directly to the unresectable remnants without affecting normal structures.