OBJECTIVE: With a prevalence up to 20 % IBS is one of the most common diseases in the western world. IBS is characterized by a combination of persistent an recurrent abdominal pain and abnormal bowel habit (diarrhoea, constipation or both). IBS is said to be the second most common cause of work absenteeism. Nevertheless, the economic burden of IBS is often underestimated. The presented study is the first one in Germany showing the burden of mixed and constipation typed IBS. METHODS: In the present study the data from 200 patient records were documented by physicians’ interviews. 100 patients were interviewed directly. Resource use in the past 12 months (physicians’ data) and 6 months (patients’ data) as well as quality of life data were documented. RESULTS: The average annual societal costs of IBS were DM 2,300.- per patient. Thereof, DM 1,729.- had to be paid by the social sickness funds. The costs increased with severity of disease (defined by subjects global assessment - SGA) from DM 1,874.- (mild) to DM 3,386.- (severe/very severe) from societal perspective and from DM 1,552.-to DM 2,703,- from health insurance’s perspective. Cost drivers were drug expenditures (33 %), inability to work (21 %) and outpatient treatment (20 %). Quality of life, documented with a generic (EQ-5D) and a disease-specific questionnaire (IBSQOL), showed that patients are severely affected by IBS. The EQ-5D tariff was decreased to 0.63. The IBSQOL showed that people are strongly discomforted in daily activities, mood and food intake. CONCLUSION: It is obvious that a reduction in severity of disease will reduce societal as well as social sickness fund costs. In a further step we will use the data to model the estimated cost savings reached through the introduction of new therapeutic options with increased effectiveness.