The National Institutes of Health Chronic Prostatitis Symptom Index (NIH-CPSI) is the standard questionnaire that determines the degree of symptoms and efficacy of treatment in patients with chronic prostatitis/chronic pelvic pain syndrome. Because there was no officially approved Japanese version of the NIH-CPSI, the Japanese Urological Association (JUA) formed a committee to develop one chaired by Dr. Masayuki Takeda, who also chairs the special field of voiding function and neurourology in the JUA. Consequently, the committee produced a Japanese version, referring to previous proposals and the Japanese version of the International Prostate Symptom Score. The committee strongly expects that the Japanese version of the NIH-CPSI will be taken full advantage of in future clinical research.