The incidence of thromboembolic events in unselected patients with class II-III congestive heart failure is 1.6-3.5% per year. Marked limitation of exercise capacity and the presence of echocardiographic left ventricular thrombus appear to be associated with an increased risk of thromboembolism. Several studies have reported that anticoagulant therapy does not eliminate the occurrence of thromboembolism. Because the benefit and risks of anticoagulant therapy in patients with congestive heart failure have not been examined in controlled studies, it is difficult to make well-founded recommendations.