Many recent mega-trials regarding atrial fibrillation have failed to prove the efficacy of antiarrhythmic drugs to improve the mortality and morbidity of patients with atrial fibrillation. Meanwhile, the upstream therapy of atrial fibrillation, the management of many components that lead to atrial fibrillation, has been paid much attention to, because its target would be the causes of atrial fibrillation itself. Among many upstream therapies, the blockade of the renin-angiotensin system would be promising from basic and clinical viewpoints, and also from rhythm management and stroke prevention.