BACKGROUND AND OBJECTIVES: Vasospastic angina is correlated with endothelial dysfunction. We compared endothelial function using flow-mediated vasodilatation (FMD) and circulating endothelial progenitor cells (EPCs) between patients with vasospasm and those without vasospasm and studied the effect of statin therapy on the changes of FMD and EPCs in vasospastic angina patients. SUBJECTS AND METHODS: In 133 patients who underwent an ergonovine provocation test, endothelial function was compared based on the presence or absence of spasm. The patients with coronary artery spasm (74 patients) were randomly assigned to either the 10 mg rosuvastatin group or the placebo group. We compared changes in the FMD and EPCs level for 6 months from the time of enrollment between the two groups. RESULTS: The incidence of cigarette smokers was higher in vasospastic angina patients than in those without spasm (p<0.001). The number of EPCs (68.6+/-36.1 vs. 103.7+/-39.3/200 microliter, p<0.001) and the FMD (7.1+/-4.5 vs. 8.6+/-3.6%, p=0.044) were significantly lower in patients with coronary artery spasm than in those without spasm. After 6 months of rosuvastatin treatment, the number of CD45(low)CD34(+) vascular endothelial growth factor receptor 2 (VEGFR2)(+) cells, which was defined as EPCs, increased significantly from 73.1+/-37.8/200 microliter to 99.1+/-37.8/200 microliter (p=0.002). The FMD was significantly ameliorated from 7.3+/-4.1 to 9.3+/-3.4% after 6 months of treatment (p<0.001). The FMD was correlated with the EPCs count before treatment (r=0.229, p=0.049) and after 6 months of treatment (r=0.268, p=0.020). CONCLUSION: The number of circulating EPCs and the FMD were reduced in vasospastic angina, and statin treatment increased the number of EPCs and the FMD. The EPCs level was correlated with the FMD.