AIM The aim of this study was to compare the efficacy and safety of alpha1-adrenoceptor (alpha1-AR) antagonist monotherapy with combination therapy using alpha1-AR antagonist and anticholinergic agent for benign prostatic hyperplasia (BPH) with storage symptoms as the chief complaint. METHODS In this prospective comparative study, either 25-75 mg/day of naftopidil monotherapy (monotherapy group) or combination therapy using 25-75 mg/day of naftopidil and an anticholinergic agent (10-20 mg/day of propiverine hydrochloride or 2-6 mg/day of oxybutynin hydrochloride; cotherapy group) were administered for 12 weeks to 101 BPH patients with storage symptoms. RESULTS International prostate symptom score (IPSS) and quality of life (QOL) index improved significantly in both groups, with no marked differences between groups. Maximum flow rate (Qmax) and residual urine volume (RUV) tended to improve in both groups, again with no marked differences between groups. However, median post-therapeutic RUV was significantly worse for the cotherapy group (45.0 mL) than for the monotherapy group (13.5 mL; P = 0.0210). Ratio of patients with increased RUV was also significantly worse for cotherapy (22.9%) than for monotherapy (5.0%; P = 0.038). CONCLUSIONS Although the anticholinergic dosage was low, the present results suggest that naftopidil monotherapy was as useful as combination therapy of naftopidil and an anticholinergic agent. Therefore, naftopidil is a useful agent as the first choice in BPH patients with storage symptoms.