Several new generation of oral anticoagulant has been tested their safety and efficacy over warfarin in patients with atrial fibrillation. These new generation of drugs have shown their superior safety over warfarin controlled with PT-INR 2-3. The real superiority of warfarin is the potential for individualization for the target PT-INR. Indeed, in the real world clinical setting, PT-INR is controlled relatively lower (around 2) in some countries such as Japan. In this context, superior safety profile shown in the clinical trials might not reflect in the real world clinical practice. It is important to accumulate data with the use of new generation of oral anticoagulant in the real world clinical practice. Moreover, risk factor control within daily life is much more important than anticoagulant intervention.