OBJECTIVES: Atrial Fibrillation (AF) is an important public health problem. The aim of the study is to assess the costs of AF in the German health care system. METHODS: From a payer´s perspective we determined annual direct medical costs of patients with paroxysmal, persistent and permanent AF based on 2008 prices. Cost calculation is based on a bottom-up approach. Resource items (e.g. laboratory tests) and quantity of resource use were identified by literature research and by consulting medical experts. Prices for outpatient treatment and drugs were obtained from official catalogues considering prices. Inpatient treatment was priced by use of the German Diagnosis Related Groups System. Costs were calculated in a cost database by relating resource use and corresponding price. Appropriate discounts and rebates were taken into consideration. RESULTS: The annual average aggregated costs of paroxysmal AF are €1394, of persistent AF are €2130 and of permanent AF are €1073 without the costs for diagnostic investigations. Including these costs there are €1644 for paroxysmal AF and €2441 for persistent AF. Permanent AF is not considered, because patients are not diagnosed as permanent by the first doctor´s contact. From payer’s perspective, the main cost driver was hospitalization (€756 to 1809), especially due to the procedures of electrical cardioversion. CONCLUSIONS: The cost evaluation shows that AF is related with high costs for the social health insurance in Germany. Because the data used are predominantly taken from publications, it might not reflect the real resource use for Germany. In the same way data raised by experts opinion do not reflect a generally applicable resource use. Despite these limitations the present study shows valid data of costs for AF in Germany. Our results are comparable with the results of another German cost-of-illness-analyses and the results of the German Competence Network on AF.