AIMS: There is evidence that antimuscarinic drugs have depressant influence not only on bladder muscle activity, but also on bladder sensations. The aim of this study was to evaluate the effect of a single dose tolterodine extended release (ER) 4 and 8 mg on bladder sensations during filling cystometry. METHODS: After approval of the local ethics committee, 30 healthy female subjects (23.7 +/- 2.3 years) were included and randomly assigned to three groups: (A) placebo, (B) tolterodine ER 4 mg, and (C) tolterodine ER 8 mg in a double blind manner. Measurements were performed at baseline and 4 hr postmedication in each group, consisting of: (1) Filling cystometry with 25 ml/min at which subjects had to indicate first sensation of filling (FSF), first desire to void (FDV), and strong desire to void (SDV). (2) Uroflowmetry and ultrasound control for residual urine. RESULTS: In the placebo group, filling volumes at FDV and SDV decreased significantly posttreatment. This effect could not be observed for the tolterodine 8 mg group and only at SDV in the 4 mg group. No significant difference between groups was found regarding uroflowmetry parameters and postvoid residual volume. CONCLUSIONS: No increase of filling volumes in healthy subjects could be observed with tolterodine. However, the results suggest that tolterodine is able to alleviate irritation caused by repeated catheterization and cystometry. There was no significant influence of tolterodine ER 4 or 8 mg on voiding function.