We evaluated the efficacy of an alpha1a/d blocker, naftopidil, on storage symptoms in patients with benign prostatic hyperplasia (BPH), using frequency/volume charts (FVC). A total of 81 patients with BPH (52-91 years, mean age 69.0 years) were studied. The inclusion criteria were: (i) one or more episode(s) of urinary urgency/day; (ii) a score of eight or more points on the International Prostate Symptom Score (I-PSS); and (iii) three or more points in any of the scores for three items (frequency, nocturia, and urgency) of the I-PSS. The patients received 50-75 mg/day of naftopidil for 6 weeks. All the patients were examined for 2-day FVC before and after the administration of naftopidil. I-PSS, quality of life index, and uroflowmetry were also evaluated. Total I-PSS decreased from 19.1 to 10.5 points (P < 0.0001), with significant improvement of both storage and voiding symptom scores (P < 0.0001, both). The score for urgency decreased from 3.1 to 1.4 (P < 0.0001). Daytime and night-time frequency decreased from 9.3 to 8.0 (P < 0.0001) and from 2.7 to 2.0 (P = 0.0009), respectively. Mean volume/void increased from 174.0 to 188.6 mL (P = 0.0453). Nocturia decreased from 3.2 to 2.3 (P < 0.0001) in 40 patients who suffered from nocturia two times or more. Notably, significant improvement of nocturia was observed in the patients both with and without nocturnal polyuria (P = 0.0006 and 0.0135, respectively). The alpha1a/d blocker naftopidil improves not only voiding symptoms but also storage symptoms, and is effective for nocturia in patients with BPH regardless of the existence of nocturnal polyuria.