Background: Salvage radiotherapy (S-RT) for patients with prostate cancer who developed PSA failure after radical prostatectomy is widely applied. However, current status of this approach in Japan has not been surveyed so far. The aim of this study was to reveal the present conditions and outcomes of S-RT for Japanese patients with biochemically recurrent prostate cancer. Methods: Clinical data of the S-RT was gathered by sending a questionnaire to participating facilities to the Japanese Radiation Oncology Study Group (JROSG). The S-RT was defined as external-beam radiotherapy delivered to the prostate bed to patients with prostate cancer who eventually developed PSA failure, although their PSA value had once reached <0.2 ng/ml after prostatectomy. In addition, the interval between prostatectomy and the S-RT should essentially be six months or longer. PSA failure-free survival (PFFS) and clinical failure-free survival (CFFS) was calculated by the Kaplan-Meier estimation. Results: 371 cases were registered from 38 facilities. Among them, hormonal therapy was combined with S-RT in 151 patients. In 3 cases, chemotherapy was combined before or after the S-RT. The rests of the cases were treated by S-RT alone. However, prognostic information was insufficient in 28 cases, and PSA nadir was >0.2 ng/ml in 3 cases. Therefore, outcome studies were conducted in the remaining 186 cases. The median age was 67 years old. The nadir value of the PSA after prostatectomy and the PSA value at the initiation of S-RT were 0.0135 ng/ml and 0.292 ng/ml, respectively. The median period between prostatectomy and the S-RT was 18.6 months. Median follow-up period was 58 months. The 5-year PFFS and CFFS were 50.1% (95%CI: 42.8 – 57.9) and 90.1% (95%CI: 86.4 – 95.7), respectively. PFFS was significantly superior in patients with PSA values <= 0.3 ng/ml at the initiation of S-RT than those of PSA values > 0.3. (57.5% vs. 40.5%, p = 0.027) Conclusions: In Japan, hormonal therapy was combined with S-RT in about 40% of the cases. The 5-year PFFS and CFFS rates of cases treated by S-RT alone were 50.1% and 90.1%, respectively. A PSA value of 0.3 was significant cut-off point for predicting PFFS.