A double-blind, randomized parallel group trial comparison involving 712 patients with irritable bowel syndrome was performed. Over a treatment period of 4 weeks hyoscine-N-butylbromide (30 mg/day p.o.) plus paracetamol (1 500 mg/day p.o.), hyoscine-N-butylbromide (30 mg/day p.o.), paracetamol (1. 500 mg/day p.o.) or placebo (3 tablets/day p.o.) were administered. Patients kept a diary and entered a daily rating of their symptoms (visual analogue scale). At the end of the four weeks 81% of the patients in the Buscopan plus group were deemed "responder" (marked or some improvement in symptoms). In the Buscopan group 76%, in the paracetamol group 72% and in the placebo group 64% of the patients were responders. The differences between the Buscopan plus group and the placebo group, and between the Buscopan group and the placebo group were statistically significant. The daily rating on the analogue scale showed a statistically significant improvement in abdominal pain intensity in the Buscopan plus group versus the placebo group and in the Buscopan plus group versus the paracetamol group. Thirty-eight patients ( = 5%, no differences between the treatment groups) experienced adverse effects, that did not require treatment. Buscopan plus and Buscopan are suitable for the treatment of the irritable bowel syndromes.