Background Previous studies have suggested that patients with low endothelial progenitor cell(EPC)counts and impaired endothelial colony forming activity have a higher incidence for cardiovascular events compared to patients with high EPC counts and favorable colony forming activity.The pathophysiological basis for this finding may be an insufficient endothelial cell repair by EPC.The objective of this study was to determine whether the number of EPCs in peripheral blood was associated with the presence and severity of angiographic stenosis in patients of the late phase after acute myocardial infarction(AMI).Methods One hundred and one patients undergoing cardiac catheterization in our hospital were enrolled in the study.The number of circulating EPCs was measured by a fluorescent-activated cell sorter(FACS).Patients with acute coronary syndromes were excluded.Results Compared with patients with normal coronary artery,the number of circulating EPCs was significantly reduced among patients in the late phase after AMI(P < 0.01).We also found that compared with the control group,the number of EPCs of single-vessel stenosis group and multi-vessel stenosis group were significantly reduced(P = 0.005;P = 0.001).Conclusions The number of EPCs in the peripheral blood is decreased in patients of the late phase after AMI.The EPCs number correlated with angiographic stenosis severity,which suggests that endothelial injury in the deficient circulating EPCs may affect the severity of the heart disorder and the clinical presentations. Background Previous studies have suggested that patients with low endothelial progenitor cell (EPC) counts and impaired endothelial colony forming activity have a higher incidence of cardiovascular events compared to patients with high EPC counts and favorable colony forming activity. The pathophysiological basis for this finding may be an insufficient endothelial cell repair by EPC.The objective of this study was to determine whether the number of EPCs in peripheral blood was associated with the presence and severity of angiographic stenosis in patients of the late phase after acute myocardial infarction (AMI) .Methods One hundred and one patients undergoing cardiac catheterization in our hospital were enrolled in the study. number of circulating EPCs was measured by a fluorescent-activated cell sorter (FACS). Patients with acute coronary syndromes were excluded. Results compared with patients with normal coronary artery , the number of circulating EPCs was significantly reduced among patie nts in the late phase after AMI (P <0.01) .We also found that compared with the control group, the number of EPCs of single-vessel stenosis group and multi-vessel stenosis group were significantly reduced (P = 0.005; P = 0.001 ) .Conclusions The number of EPCs in the peripheral blood is decreased in patients of the late phase after AMI. EPCs number correlated with angiographic stenosis severity, which suggests that endothelial injury in the deficient circulating EPCs may affect the severity of the heart disorder and the clinical presentations.