Objective:To investigate the effect of angiotensin Ⅱ(Ang-Ⅱ) on numerous of endothelial progenitor cells(EPCs) in acute myocardial infraction(AMI). Methods:Twenty-eight patients with AMI and 30 controls with negative results of coronary artery angiography were selected in the study. The concentration of Ang-Ⅱ and stromal cell-derived factor-1α(SDF-1α) in different periods of patients was determined with immunosorbent assay(ELISA). Circulating EPCs were stained with anti-CD34,VEGF and CD133 antibodies,and then the ratio of EPCs to plasma mononuclear cells was analyzed by three-colour flow cytometry. Results:The concentration of Ang-Ⅱ in acute stage of AMI patients was(90.40 ± 6.39) pg/ml and higher than that of AMI patients in recovery stage[(72.57 ± 2.42)pg/ml] and control group[(69.14 ± 3.73)pg/ml](P = 0.002 4). But the concentration of SDF-1α of AMI patients in acute stage was (171.10 ± 35.81)pg/ml and had not significant difference with that of AMI patients in recovery stage[(130.30 ± 28.84)pg/ml] and control group[(116.50 ± 29.19)pg/ml](P = 0.370 3). Circulating EPCs were significantly increased in acute stage of AMI patients[(0.043 ± 0.004)%]compared with the recovery stage of AMI patients[(0.024 ± 0.010)%]and control group[(0.012 ± 0.001)%](P < 0.000 1). In acute stage of AMI patients,circulating EPCs had negative correlation with the concentration of Ang-Ⅱ (r = -0.801,P < 0.001),but had no correlation with the concentration of SDF-1α(r = -0.076,P = 0.702). Conclusion:Quantity of EPCs and concentration of Ang-Ⅱ increased in acute stage of AMI patients,but Ang-Ⅱ could reduce the quantity of EPCs.