We investigated the effect of naftopidil an alpha1 adrenoceptor antagonist on non-bacterial chronic pelvic pain syndrome (CPPS) in middle-aged and older male patients with lower urinary tract symptoms (LUTS). Patients who had given informed consent were treated with naftopidil (daily 50 mg), and were evaluated using the Japanese edition of NIH chronic prostatitis symptom index (NIH-CPSI) and the international prostate symptom score (IPSS) at 2 and 4 weeks after the administration. The NIH-CPSI (total score) was significantly improved by naftopidil for 4 weeks (11.5+/-6.0, n=62, p<0.001) as compared with the baseline (19.8+/-5.7). Other items of NIH-CPSI of pain, urinary symptoms, and quality of life-impact, and IPSS were also ameliorated by naftopidil as compared with the baseline (n=62, p<0.001 each). One patient had slight dizziness, but no severe adverse events were noted in any patient. It is suggested that naftopidil could be an effective and safe therapeutic option for middle-aged and older male LUTS patients with CPPS.