A randomized controlled trial has started in Japan to evaluate radiotherapy and endocrine therapy for prostate-specific antigen (PSA) failure after radical prostatectomy. Patients who have PSA failure after radical prostatectomy for localized prostate cancer (T1-2N0M0) are randomized into treatment groups of either radiotherapy +/- endocrine therapy or endocrine therapy alone. The Urologic Oncology Study Group (UOSG) in the Japan Clinical Oncology Group (JCOG) composed of 36 specialized institutions will recruit 200 patients. The primary end-point is time to treatment failure (TTF) of bicalutamide, and secondary end-points are TTF of protocol treatment, progression-free survival, overall survival, adverse events and quality of life (QOL). The Clinical Trial Review Committee of the JCOG approved the protocol on April 13, 2004, and the study was activated on May 17, 2004.