Abstract We examined the effects of propiverine hydrochloride and naftopidil on the urinary ATP level and bladder activity after bladder stimulation in rats. Thirty-nine female rats were divided into a control group, a propiverine group, and a naftopidil group. Rats in the propiverine and naftopidil groups were administered 1 ml/day of propiverine or naftopidil dissolved in water at 5 mg/ml, while animals in the control group were administered 1 ml of water only. After 2 weeks, 18 rats (6 per group) underwent continuous cystometry with physiological saline or 0.1% acetic acid solution and their bladder activity was recorded. In the remaining 21 rats (7 per group), 0.1% acetic acid solution was infused into the bladder and the urinary ATP level was measured before and after stimulation (days 0–7). During cystometry with acetic acid in the control group, the interval between bladder contractions was shorter and the maximum bladder contraction pressure was higher than the results for cystometry with physiological saline. The maximum bladder contraction pressure was also increased in the naftopidil group, but such a change was not seen in the propiverine group. The urinary ATP level increased significantly in all three groups after the infusion of acetic acid, but the increase of ATP was smaller in the propiverine group (45% of control) and the naftopidil group (62% of control) than in the control group on day 0. Therefore, the inhibitory effect of propiverine and naftopidil on bladder activity may be partly due to blocking ATP release from the bladder epithelium.