Between 1965 and 1982 definitive external beam radiation therapy was given to 114 patients with clinically Staged A2 (32 patients) and B (82 patients) adenocarcinoma of the prostate. These patients were not considered to be surgical candidates because of age, comorbidity or disease extent, or because they had refused surgery. Total prostatic doses ranged from 60 to 70 Gy. For 90 surviving patients, follow-up duration ranged from 32 to 188 months with a median of 5 years. The 5- and 10-year uncorrected survival rates for all patients, which were 89% and 68% respectively, were no different from the survival expectation of age-matched men in the general population. Disease-free survival rates at the same time periods were 89% and 86%. There were no significant differences in disease-free survival between Stage A2 and Stage B. Four patients (3.5%) developed local recurrence. Bone metastases, which occurred in 9 of 11 treatment failures were the predominant cause of failure. An analysis of 11 potential prognostic factors was fruitless. Pelvic node irradiation did not improve the outcome. The incidence of complications was acceptable. Anorectal problems developed in 20% of patients and urinary manifestations occurred in 20%, and only 2 patients (1.8%) developed serious problems. We concluded that localized external beam high-energy radiation therapy provides excellent local control for disease limited to the prostate, with survival rates that rival those of radical surgery.