Our objectives were to ascertain the tolerability and efficacy of trospium chloride in doses of 20 mg twice daily for long-term therapy (52 weeks) in patients with urge syndrome. The trial comprised a total of 358 patients with urge syndrome or urge incontinence. After randomisation in the ratio of 3:1, participants were treated continuously for 52 weeks with either trospium chloride (20 mg twice daily) or oxybutynin (5 mg twice daily). At intervals of 4-8 weeks, patients were physically examined with measurements of blood pressure and pulse rate, were questioned about any adverse events, checked for compliance and underwent relevant laboratory tests. As an additional safety measure, an ECG was made at 26 and 52 weeks. Urodynamic measurements were performed at the beginning, and at 26 and 52 weeks to determine the maximal cystometric bladder capacity. Among others things, the frequencies of micturition, incontinence and number of urgency events were recorded in patient diary protocols in weeks 0, 2, 26 and 52. The evaluation of vital parameters, laboratory results and ECGs did not show any relevant changes attributable to the action of the anticholinergics. Analysis of the micturition diary clearly indicated a reduction of the micturition frequency, incontinence frequency, and a reduction of the number of urgencies in both treatment groups. Mean maximum cystometric bladder capacity increased during treatment with trospium chloride by 92 ml after 26 weeks and 115 ml after 52 weeks (P=0.001). Further comparison with oxybutynin did not reveal any statistically significant differences in urodynamic variables between the drugs. Adverse events occurred in 64.8% of the patients treated with trospium chloride and 76.7% of those treated with oxybutynin. The main symptom encountered in both treatment group was dryness of the mouth. For patients on trospium chloride, the estimated risk of an unexpected adverse event was 0.027 per patient per week for all adverse events and 0.009 for dryness of the mouth, resulting in a considerably lower risk during treatment given with trospium chloride than with oxybutynin (0.045 and 0.021, respectively). An overall assessment for each of the drugs reveals a comparable efficacy level and a better benefit-risk ratio for trospium chloride than for oxybutynin due to better tolerability.