The success following irradiation in 370 patients with clinically localized prostate carcinoma was measured by overall patient survival as well as the cumulative incidence with time of treated patients who developed either local tumor regrowth or progression with distant metastases. With a minimum follow-up of 5 years in living patients, we evaluated the cumulative frequency curves using both univariate and multivariate (Cox) analyses. Overall patient survival and probability of progression with distant metastases were significantly influenced by initial tumor stage and the degree of histologic differentiation. The results at 8 years are significantly better for patients with T2 (B) tumors (local regrowth in 8%, distant metastases in 18%) than for patients with T3-T4 (C) tumors (local regrowth in 28%, distant metastases in 60%). Patient tolerance of external-beam radiation therapy was carefully analyzed in 121 consecutively treated patients in 1980 and 1981 for subsequent radiation-related sequelae. Minor transient intestinal and urologic sequelae were observed in 21% and 23% of the patients, respectively. These mild to moderate symptoms resolved in all but 7% of the patients who are continuing with mild symptoms. One patient had a major complication, i.e., a cystectomy required for persistent bleeding. Erectile potency has been maintained in 63% of potent patients. No specific benefit or detriment in outcome was seen in the minority of 51 patients who were irradiated by iodine-125 implantation.(ABSTRACT TRUNCATED AT 250 WORDS)