Background. The incidence of pathologic upstaging to stage T3 is a common occurrence in patients undergoing radical prostatectomy for clinical stage T1-2 prostate cancer. There is a considerable risk of local recurrence following radical prostatectomy for pathologic stage T3 cancers. Postoperative adjuvant radiation therapy has been used to reduce the incidence of local recurrence. Methods. The available data in series using radiation therapy following radical prostatectomy are reviewed. Results. The available data demonstrate that adjuvant pelvic radiation therapy reduces the risk of clinical local failure from 30-60% to 0-10% in patients with high risk pathologic features following radical prostatectomy. Most patients who receive radiation therapy to the pelvis for a persistently elevated serum prostate specific antigen (PSA) level following radical prostatectomy will have a subsequent decrease in the serum PSA level. The incidence of severe complications related to postprostatectomy radiation therapy is 5-10%, and there is no evidence that the risk of incontinence or urethral stricture is increased with the addition of radiation therapy. Conclusions. Radiation therapy following radical prostatectomy can reduce the rate of clinical local failure in patients with high risk features following radical prostatectomy. Radiation therapy can be administered following radical prostatectomy with acceptable treatment-related morbidity. There is no evidence that postprostatectomy radiation therapy improves disease free survival.