PURPOSE: We investigated bladder function, with a special focus on nonvoiding contractions (NVCs), in awake rats with chronic chemical cystitis and bladder outlet obstruction (BOO) by use of simultaneous registrations of intravesical and intraabdominal pressures. In addition, we tested the effects of tolterodine on the NVCs in these models. METHODS: A total of 20 female Sprague-Dawley rats were used in this study. In eight rats, chemical cystitis was induced by intravesical instillation of HCl. Twelve rats were subjected to sham instillations or partial BOO. Four weeks after intravesical instillation or 2 weeks after partial BOO, cystometrograms were obtained by use of simultaneous recording of intravesical and intraabdominal pressure in all unanesthetized, unrestrained rats in metabolic cages. RESULTS: A total of 17 rats survived. In the rats with acute injury by HCl, 50% showed detrusor overactivity (DO), which was not seen in the sham group. The cystitis group had lower DO pressure without a difference in DO frequency compared with the BOO group. After the administration of tolterodine, the cystitis group showed no difference in DO frequency or pressure, whereas the BOO group showed decreased values for both parameters. CONCLUSIONS: Our study showed that toleterodine produced no effect on DO during the filling phase in rats with chronic chemical cystitisbut decreased the frequency and pressure of DO in rats with BOO. Clinically, studies are needed to improve the treatment effect of anticholinergic drugs ininterstitial cystitis patients with overactive bladder.