Background: Occlusive coronary artery spasm can induce acute myocardial infarction (AMI). Circulating endothelial progenitor cells (EPCs) are known to be involved in vasculogenesis and endothelial dysfunction. We investigated the relation between the circulating endothelial progenitor cell (EPC) and the development of AMI in patients with coronary vasospasm. Methods: We enrolled 60 patients (57.4짹10.7 years, male 60.0 %) with documented coronary vasospasm by ergonovine provocation test. The number of EPC and the levels of serum vascular endothelial growth factor (VEGF), macrophage chemoattractant protein (MCP-1), and interleukin-10 (IL-10) were measured in the peripheral blood before PCI. The paitents were devided into two groups: acute myocardial infarction (group I: n=24) and angina pectoris (group II: n=36). Results: The levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP), peak Creatine kinase-MB (CK-MB), peak troponin I (TnI), and homocysteine were significantly higher in the group I than those in the group II (p=0.020, p=0.005, p<0.001, p=0.003, respectively). Also, the levels of total cholesterol and low density lipoprotein cholesterol were significantly higher in the group I compared with those of the group II (p=0.013, p<0.001, respectively). The level of MCP-1 was significantly higher in the group I than that in the group II (52.2짹19.0 vs. 32.7짹16.4 pg/mL, p=0.002). The levels of VEGF and IL-10 were no significant differences. CD34+VEGFR2+ cells and CD45lowCD34+VEGFR2+ cells were significantly lower in the group I than those of the group II (401.9짹341.5 vs. 683.8짹347.1/106 leukocyte, p=0.045; 91.6짹123.1 vs. 326.8짹221.4/106 leukocyte, p=0.004, respectively). CD45lowCD34+VEGFR2+ cells correlated positively with Apolipoprotein A1 level (r=0.443, p<0.001) and negatively with the levels of fibrinogen. high-sensitivity C-reactive protein, lipoprotein (a) (r= -0.233, p=0.044; r= -0.433, p<0.001; r= -0.255, p=0.028, respectively). In multivariate analysis, the decreased CD45lowCD34+VEGFR2+ cell and the increased MCP-1 level were independent determinants for the AMI due to occlusive vasospasm (OR, 3.33, 95% CI 1.34-9.80, p<0.001; OR, 5.00, 95% CI 1.28-19.53, p=0.021, respectively). Conclusion: Decreased number of endothelial progenitor cell and elevated level of MCP-1 were associated with AMI due to occlusive coronary spasm, suggesting that they may play important roles in the genesis of thrombotic coronary occlusion subsequent to coronary spasm.