AIM: To investigate the clinical efficacy of acotiamide hydrochloride hydrate in patients with detrusor underactivity. METHODS: We measured the post-void residual urinary volume in 19 patients with underactive bladders. All these patients had been under treatment with distigmine bromide and were prescribed acotiamide hydrochloride hydrate at a dose of 100 mg three times daily for 2 weeks. RESULTS: Compared with the post-void residual urinary volume value at baseline (161.4±90.0 mL) a statistically significant reduction was observed at the end of treatment (116.3±63.1 mL) (P=0.006). The drug was generally well tolerated by the majority of patients. CONCLUSION: Maybe, acotiamide hydrochloride hydrate showed clinical efficacy in patients with underactive bladders and may, therefore, be used alternatively in patients who do not respond sufficiently to distigmine bromide.