Aim : This study was designed to test the hypothesis that propofol, ketamine, and midazolam could alter the contractile activity of detrusor smooth muscle. Materials and Methods : Four detrusor muscle strips isolated from each rat bladder (n = 12) were placed in 4 tissue baths containing Krebs-Henseleit solution. The carbachol (10 -8 to 10 -4 mol/L)-induced contractile responses as well as 5, 10, 20, 30, 40, 50 Hz electrical field stimulation (EFS)-evoked contractile responses of the detrusor muscles were recorded using isometric contraction measurements. After obtaining basal responses, the in vitro effects of propofol, ketamine, midazolam (10−5 to 10−3 mol/L), and saline on the contractile responses of the detrusor muscle strips were recorded and evaluated. Results : All the 3 drugs reduced the carbachol-induced and/or EFS-evoked contractile responses of rat detrusor smooth muscles in different degrees. Midazolam (10−4 to 10−3 mol/L) caused a significant decrease in the contractile responses elicited by either EFS or carbachol (P=0.000-0.013). Propofol (10−3 mol/L) caused a decrease only in EFS-evoked contractile responses (P=0.001-0.004) and ketamine (10−3 mol/L) caused a decrease only in carbachol-induced contractile responses (P=0.001-0.034). Conclusion : We evaluated the effects of the 3 different intravenous anesthetics on detrusor contractile responses in vitro and found that there are possible interactions between anesthetic agents and detrusor contractile activity. The depressant effects of midazolam on the contractile activity were found to be more significant than ketamine and propofol. Despite the necessity of further studies, it could be a piece of wise advice to clinicians to keep the probable alterations due to intravenous anesthetics in mind, while evaluating the results of urodynamic studies in children under sedation.