Method:Patients with IBS, fulfilling Rome III criteria, and aged between 18 and 70, were recruited from the University Hospital of Vienna, from primary care physicians and the Austrian IBS patients' organisation by an information letter with an invitation to participate in this RCT. Patients were invited for an interview at the University hospital to confirm the IBS diagnosis according to the guidelines. Exclusion criteria were: pregnancy, bowel surgery, mental retardation, insufficient knowledge of German, a concomitant severe organic and/or psychiatric disease, and recently indicated treatment with anti-depressants. Anti-depressants at a stable dose for longer than three months were allowed for admission to the study. The time for patients to reach the hospital was not to be longer than one hour. Patients with lactose and fructose intolerance as diagnosed by breath tests were not excluded if they had had an adequate diet over a period of more than three weeks without any change of their IBS symptoms.