We cross-sectionally studied the incidence and impact on quality of life of ejaculatory disorders caused by alpha-1 adrenoceptor antagonists (tamsulosin or naftopidil) in patients with benign prostatic hyperplasia (BPH). By questionnaire, we queried 88 clinical BPH patients concerning ejaculatory disorders, who were treated with tamsulosin or naftopidil between February 1999 and August 2003. We investigated the difference in the incidence and types of disorders between the two drugs. Of the 88 patients, 63 (71.6%) had sexual activities during the treatment. The incidence of ejaculatory disorders was significantly higher in the tamsulosin group (30.0%) than in the naftopidil group (3.0%). Eighty percent of patients having the disorders noticed the absence or reduced volume of semen although they experienced orgasms. The median quality of life index concerning the disorder was rated as 4, "mostly dissatisfied." Our results indicated that ejaculatory disorders occurred more frequently in the tamsulosin group. We should inform patients about this adverse effect caused by alpha-1 adrenoceptor antagonists prior to treatment.