Between 1976 and 1989, 114 patients undergoing radical retropubic prostatectomy and bilateral pelvic lymph node dissection for prostatic adenocarcinoma were found to have stage PcN0 lesions. Postoperative adjuvant radiation therapy without hormonal treatment was given to 95 of these patients (83%): 26 (27%) with stage C1, 37 (39%) with stage C2 and 32 (34%) with stage C3 disease. The median radiation dose was 45 Gy. given at 180 cGy. daily. Median followup was 4.4 years (range 1.4 to 13.3). The overall 5 and 10-year actuarial rates for the patients were 94% and 70%, respectively. Disease-specific 5 and 10-year actuarial survival rates were 99% and 78%, respectively. At 5 and 10 years the chance of clinical recurrence was estimated as 6% and 13%, respectively, and the chance of recurrence (clinical or indicated by prostate specific antigen levels) was estimated to be 34% and 46%, respectively. Patients with high Gleason scores (8 to 10) and seminal vesicle involvement (stage C3) fared worst. There were 5 patients with clinical distant metastases, 1 with a clinical local recurrence and 1 with both conditions. Detectable elevation of prostate specific antigen without clinically evident recurrence was noted in 25 patients. Radiation therapy was well tolerated with minimal morbidity. Disease-specific survival and survival without clinical recurrence were improved over historical control in patients with stage PcN0 prostate cancer treated by radical prostatectomy alone. These data support a role for adjuvant radiation therapy in stage PcN0 prostate adenocarcinoma following radical prostatectomy.