Optimal treatment for patients with localized carcinoma of prostate is controversial. Radiation therapy is an established modality; reports indicate that results are comparable to those of radical prostatectomy. A retrospective review was carried out of 963 patients with carcinoma of the prostate treated with definitive irradiation (65 to 71 Gy in 6.5 to 7 weeks). Survival, incidence of local recurrence and distant metastases, and postirradiation PSA data were analyzed. Ten-year disease-free survival with external irradiation was 100% for clinical stage A1 (T1a), 69% for stage A2 (T1b,c), 57% for clinical stage B (T2), and 41% for stage C (T3). Initial PSA level closely correlated with probability of freedom from chemical failure (PSA elevation) after definitive irradiation in 317 patients with stage T1b,c and T2 tumors (96% and 89%, respectively, with initial PSA of < 10 ng/ml and 75% and 65% with higher PSA levels). Although modern irradiation techniques produce results comparable to those of radical prostatectomy in localized prostate carcinoma, we must continue to critically assess treatment policies, develop appropriately designed prospective clinical trials, and define optimal management of these patients.