[en] We assessed the variations in stage, prostate specific antigen at diagnosis, Gleason score, risk classification and primary therapy in Japanese prostate cancer patients, and compared with those of the United States (US) patients. Between 2004 and 2006, the distribution of primary therapy and clinical characteristics of 2303 newly diagnosed patients at Nara Medical University and its 23 affiliated hospitals were assessed to compare with those of the Cancer of the Prostate Strategic Urological Research Endeavor data and to clarify the differences in data between the USA and Japan. The proportions of clinical T stage of 3-4, prostate specific antigen at diagnosis >20 ng/ml, Gleason score of 8-10 and high-risk group were greater in our study than those of the Cancer of the Prostate Strategic Urological Research Endeavor data (T3-4, 26.2 vs. 3.5-11.8%; prostate-specific antigen, 34.1 vs. 8.1-27.0%; Gleason score, 29.3 vs. 9.7-12.1%). Regarding the primary treatments, 51% of patients received primary androgen deprivation therapy, 30% underwent radical prostatectomy, 14% received radiation therapy and 2% had watchful waiting in our study, while the corresponding figures in the Cancer of the Prostate Strategic Urological Research Endeavor data were: radical prostatectomy, 44%; radiation therapy, 23%; primary androgen deprivation therapy 20% and watchful waiting 10%. The Japanese prostate cancer patients still have higher prostate-specific antigen at diagnosis, higher Gleason score and higher clinical stage than the US patients. The trends of primary therapy for prostate cancer were different from those in the USA. The higher rate of primary androgen deprivation therapy is characteristic for the Japanese patients. (author)