OBJECTIVE: Irritable bowel syndrome (IBS) is associated with increased use of health care services. This study aims to estimate the costs of IBS in relation to differing diagnostic criteria of IBS, duration of symptoms, gender, and age. MATERIAL AND METHODS: A two-phase postal survey. Questionnaire I covering gastrointestinal (GI) symptoms by Manning and Rome II criteria was mailed to 5000 randomly selected adults. Questionnaire II, mailed to those fulfilling IBS criteria of Questionnaire I, recorded data on physician visits, medications, and diagnostic procedures performed. RESULTS: Proportion of GI consulters was 48% (95% CI 41-55%) and 32% (95% CI 28-36%) for Rome II and Manning groups. Annual GI related individual costs were euro 497 (95% CI euro 382-621) and euro 295 (95% CI euro 246-347) by Rome II and Manning criteria. Societal GI costs were euro 82 million and euro 154 million by Rome II and Manning criteria. Direct non-GI costs amounted to euro 43 million and euro 126 million by Rome II and Manning criteria. Duration of GI symptoms, gender, or age had no impact on GI costs. CONCLUSIONS: IBS incurs substantial GI and non-GI costs corresponding to a share of up to 5% of the national direct outpatient and medicine expenditures. The more restrictive Rome II criteria identify an IBS population incurring higher GI related individual costs than Manning criteria. Costs due to GI endoscopies are not lower for those with a long history of symptoms suggesting that guideline recommendations for avoiding repeated diagnostic procedures may not be followed.