Morbidity and mortality associated with atrial fibrillation are mainly related to thromboembolic complications, particularly ischemic strokes. The prevention of thromboembolism is an important component in the management of patients with atrial fibrillation. The choice of optimum antithrombotic therapy for a given patient depends on the risk of thromboembolism, on the one hand, and the risk of intracerebral hemorrhage, on the other hand. Concerning the benefit-to-risk stratification the problem lies in the similar and sometimes even identical risk factors for both thromboembolism and haemorrhage.At present, oral vitamin K antagonists are recommended for patients with atrial fibrillation at moderate or high risk of ischemic stroke. The thromboembolic risk should be assessed using validated stratification schemes, such as the CHADS(2) score. Aspirin alone is recommended for patients at low risk of thromboembolic complications. A combination of anticoagulant and antiplatelet drugs is necessary in patients with atrial fibrillation undergoing percutaneous coronary intervention and stent implantation, but the optimal therapeutic management of these patients has not yet been defined. Hopefully, the development of new antithrombotic agents being easier to use and having a superior benefit-to-risk ratio will extend effective prevention of thromboembolic events to a greater part of the atrial fibrillation population at risk.