We administered adjuvant radiation therapy to 56 selected patients with carcinoma of the prostate whose disease was upstaged to stage C or D1 after radical prostatectomy and pelvic lymphadenectomy. The complications associated with radiation therapy were minimal. The local recurrence rate was 2% after mean follow-ups of 67 and 53 months for patients with stage C and D1 disease, respectively. The actuarial 5-year survival rate free of disease was 76% for patients with stage C and 72% with stage D1a cancer. Further exploration of the role of adjuvant radiation therapy in the treatment of patients with pathological stage C or D1a disease is warranted.