OBJECTIVES: Atrial fibrillation (AF) is an arrhythmia that progressively worsens and is characterized by uncoordinated atrial activation involving a rapid and irregular heart rate (Fuster et al. 2006). AF patients are likely to have concomitant congestive heart failure (CHF) and stroke (Lee et al. 2008). The prevalence of AF in adults ≥65 years is 5 - 6%, increasing with age (Go et al. 2001). The purpose of this study was to estimate the economic burden of AF in selected developed countries based on prevalence and direct health care costs. METHODS: The economic burden of AF in the United States (US), Canada, Germany, France, United Kingdom and Italy was modeled based on prevalence rates identified via a literature search. Annual probabilities of receiving health care treatment and associated costs for AF, stroke and CHF, and related disability costs were included in the model. If cost data were unavailable, the costs were imputed based on the ratio of annual per capita health expenditures between the United States and the country of interest. Cost estimates were calculated in 2010 rates of the local currencies. RESULTS: The prevalence of AF in adults aged ≥65 in the countries studied was: 172,000 in Canada; 328,000 in the United Kingdom; 348,000 in France; 391,000 in Italy; 533,000 in Germany; and 1.6 million in the United States.  The estimated annual economic burden of AF was: 597 million in Canada; 596 million in the United Kingdom; 1.23 billion in France; 840 million in Italy; 1.58 billion in Germany; and 9.75 billion in the United States (2010 local currencies). CONCLUSIONS: The economic burden of AF in developed countries is substantial, and is expected to grow as the population ages. Early detection and appropriate management of AF may help reduce this economic burden.