Atrial fibrillation (AF) in hypertrophic cardiomyopathy (HCM) is associated with increased mortality, mainly mediated by increased thromboembolic events and progressive heart failure. Many studies suggested inhibition of renin-angiotensin-aldosterone system (RAAS) could reduce new AF in various clinical conditions. However, evidence concerning the effects of RAAS inhibitors on AF prevention remains unclear in HCM. Our study is to investigate whether treatment with ACE inhibitors (ACEIs) or angiotensin-receptor blockers (ARBs) could lower the risk of new AF in HCM.