AIM: To determine the prevalence, symptom pattern and impact of the irritable bowel syndrome, across eight European countries, using a standardized methodology. METHODS: A community survey of 41 984 individuals was performed using quota sampling and random digit telephone dialing to identify those with diagnosed irritable bowel syndrome or those meeting diagnostic criteria, followed by in-depth interviews. RESULTS: The overall prevalence was 11.5% (6.2-12%); 9.6% had current symptoms, 4.8% had been formally diagnosed and a further 2.9%, 4.2% and 6.5% met the Rome II, Rome I or Manning criteria, respectively. Bowel habit classification varied by criteria: 63% had an 'alternating' bowel habit by Rome II vs. 21% by self-report. On average, 69% reported symptoms lasting for 1 h, twice daily, for 7 days a month. Irritable bowel syndrome sufferers reported more peptic ulcer (13% vs. 6%), reflux (21% vs. 7%) and appendectomy (17% vs. 11%), but not hysterectomy, cholecystectomy or bladder procedures. Ninety per cent had consulted in primary care and 17% in hospital; 69% had used medication. Irritable bowel syndrome substantially interfered with lifestyle and caused absenteeism. CONCLUSIONS: Irritable bowel syndrome is common with major effects on lifestyle and health care. The majority of cases are undiagnosed and the prevalence varies strikingly between countries. Diagnostic criteria are associated with varying prevalences and bowel habit sub-types. This limits their utility in clinical practice and the transferability of research findings using them.