Atherosclerotic vulnerable plaque is considered as an important pathologic basis of acute coronary syndrome and sudden cardiac ischemic death.Vulnerable plaque is characterized with endothelial denudation and thrombosis.The mechanisms of vulnerable plaque are poorly understood.Recent researches demonstrated that endothelial progenitor cells play an important role in repair of injured endothelium.So the role of endothelial progenitor cells in the process of atherosclerotic vulnerable plaque is worth investigating.