A total of 100 patients with benign prostatic hyperplasia (BPH) and overactive bladder (OAB) symptoms (BPH/OAB), enrolled between June 2006 to March 2008, were randomly divided into 2 groups of morning medication (M) and evening medication (E) groups, then 50 mg of naftopidil was given once a day after breakfast or supper for 8 weeks. Data were available for efficacy analysis on 80 patients (M group ; 43, E group ; 37). Naftopidil significantly improved the overall international prostatic symptom score ; from 19.2±7.9 to 11.7±5.8 in the M group and from 19.4±6.4 to 12.3±6.8 in the E group (p<0.0001), QOL score from 4.9±0.8 to 3.2±1.4 in the M group and from 5.0±0.8 to 3.6±1.3 in the E group (p<0.0001), and OAB symptom score from 7.8±2.6 to 5.0±2.5 in the M group (p<0.0001) and from 8.6±2.9 to 5.8± 3.3 in the E group (p<0.0001). There was no significant difference in the incidence of adverse effects between the M group (6.1%) and E group (2.2%). These results suggest that naftopidil improves storage symptoms as well as voiding symptoms regardless of timing of administration.