Thirty-four patients with carcinoma of the prostate treated by prostatectomy received postoperative external beam radiation. Sixteen patients were treated within 4 months of radical prostatectomy (group 1), 12 patients were treated for prostate carcinoma following initial enucleative prostatectomy for benign hypertrophy (group 2) and 6 patients were treated for palpable local recurrence 4 to 10 years following radical prostatectomy (group 3). The indications for postoperative radiotherapy following radical prostatectomy included extracapsular extension, seminal vesicle invasion, peri-prostatic soft tissue involvement, positive margins or palpable local recurrence. Eighty-five percent of the patients received whole pelvic radiation. All patients then had a 2-week treatment rest followed by a reduced portal to the prostate bed to a dose of 6500 cGy. The local control rate after radiotherapy was 100% with a median follow-up of 4 years. The 5-year actuarial survival and disease-free survival rates for all patients were 82 and 72%, respectively. In group 1, the 5-year actuarial survival and disease-free survival rates were 100 and 91%, respectively. In group 2, these rates were 77 and 64%. Three of the six patients in group 3 died within 30 months of radiotherapy. Fourteen patients (41%) had mild to moderate treatment related symptoms including seven patients (21%) with lower extremity or genital edema, five patients (15%) with urinary stress incontinence, two patients (6%) with urethral stricture and three patients (9%) with proctitis. Six of eight patients who were potent prior to radiation retained potency thereafter. No severe complications occurred. We conclude that external beam radiation therapy administered after prostatectomy resulted in an acceptable therapeutic ratio with 100% local regional control, and an acceptable complication rate (41%).