Abstract： Objective To explore the relationship between distensibility of large arteries,endothelial function and coronary event in young patients with acute coronary syndrome.Methods According to clinic data,there were divided into 3 groups:young patients with ACS group(n=44),young patients with no ACS group (n=49) and health control group(n=50).Automatic pulse wave velocity measuring system(Complior) was applied to examine carotid-femoral PWV as an index reflecting distensibility of large arteies.Ultrasound (ALOKA5500) was applied to examine the flow-mediated vasedilataion of the brachial artery as an index reflecting endothelial function and the widening of internal diameter of brachial artery using nitroglycerin as index reflecting non-endothelial-dependent blood vessel dilation.Results Distensibility of large arteries and endothelial function in group of young patients with acute coronary syndrome was significantly lower than that of other groups (P＜0.05).A significant positive correlation between distensibility of large arteries,endothelial function and coronary event was found in all of the subjects(respectively,r=0.359,P＜0.05;r=0.427,P＜0.05).Conclusion Distensibility of large arteries and endothelial function are indicative indexes for acute coronary syndrome,they seriously promote artherosclerosis,and might perhaps cause atherosclerosis plaque destory.