A progress report on the treatment of 116 patients with adenocarcinoma of the prostate treated by external irradiation is presented. Fifteen, 60, and 41 patients presented initially with Stages A, B, and C, respectively. The majority of the patients received 7,000-7,500 rads during a period of seven to eight weeks, locally to the prostate gland. The five-year actuarial survival were 90, 70, and 40 per cent for Stages A, B, and C, respectively. The five-year survival rates for patients with well and moderately differentiated tumors were significantly better (45 per cent) than for those with poorly differentiated tumors (24 per cent). The five-year survival rate in the patients who received prior or concomitant hormone manipulation was lower (33 per cent) as compared with those receiving radiation therapy alone (43 per cent). All of the above differences were statistically significant (0.01 level). Of the patients failing, distant metastases have developed in 88 per cent suggesting that subclinical distant metastases might have been present prior to initiation of radiotherapy. The local control rate was 82 per cent. The morbidity of this mode of therapy was found to be acceptable. Radical radiation therapy is an effective method for control of carcinoma of the prostate and is potentially curative.