Patients with chronic kidney disease (CKD) have an increased risk for cardiovascular morbidity and mortality. Little attention has been paid to the problem of atrial fibrillation, although this arrhythmia is very frequent with a prevalence of 13 to 27% in patients on long-term hemodialysis. Because of the large number of pathophysiologic mechanisms involved, these patients have a high risk for both thromboembolic events and hemorrhagic complications. Stroke is a frequent complication in CKD: The US Renal Data System reports an incidence of 15.1% in hemodialysis patients compared with 9.6% in patients with other stages of CKD and 2.6% in a control cohort without CKD. The 2-yr mortality rates after stroke in these subgroups were 74, 55, and 28%, respectively. Although oral coumadin is the treatment of choice for atrial fibrillation, its use in patients with CKD is reported only in limited studies, all in hemodialysis patients, and is associated with a markedly increased rate of bleeding compared with patients without CKD. With regard to the high risk for stroke and the conflicting data about oral anticoagulation, an individualized stratification algorithm is presented based on relevant studies.