This study evaluated the 5-year failure rate of naftopidil (NAF) or tamsulosin hydrochloride (TAM) in lower urinary tract symptoms associated with benign prostatic hyperplasia (BPH/LUTS) and compared the prognostic factor of two alpha(1)-blockers. A total of 131 patients with International Prostate Symptom Score (IPSS) >or= 8 or IPSS quality of life (IPSS-QOL) >or= 3 with BPH/LUTS receiving treatment with alpha(1)-blockers had been administered NAF or TAM, and failure rates were calculated for 5 years. Age, prostate volume (PV), acute urinary retention (AUR), overactive bladder (OAB), IPSS, IPSS-QOL and postvoiding residual volume (PVR) were evaluated as prognostic factors. No significant differences in failure rate were observed between the drugs. The failure rate was significantly high for patients with a PV >or= 35 ml, PVR >or= 30 ml, a history of AUR or complications of OAB symptoms. The failure rate for patients with a history of AUR was significantly higher than in those without AUR in the NAF group. By contrast, in the TAM group, it was significantly higher in patients who had OAB symptoms than in those without OAB. No significant differences were observed between the drugs for the failure rate. Each treatment had a unique factor for prognosis, such as history of AUR for NAF and complications of OAB for TAM. Therefore, it will be necessary to use the two alpha(1)-blockers properly, considering the patient's background.