Atrial fibrillation (AF) is supraventricular tachyarrhythmia characterized by uncontrolled atrial activation, and deteriorates atrial function. In AF patients, increasing of age is related with enlarge left atrium (LA), diminished flow velocity of left atrial appendage (LAA), and spontaneously contrast echo, with other factors which are predisposition for LA thrombus. In AF patients, thromboemboli after cardioversion without anticoagulant administration is 1.5-3.0%. Elderly patient is not contraindication for anticoagulant, although higher risk for bleeding. For stroke prevention in >65 years of age whilst the patient is candidate for oral anticoagulant warfarin, it should be prescribed to reach INR 2.0-3.0. Some reports on anticoagulant evaluation (INR) and bleeding as complication of warfarin prescribed for AF treatment are not significantly different in elderly and younger patients.