Conclusion: Endothelial progenitor cells positive for CD-34 and kinase domain receptor (KDR) predict occurrence of death from cardiovascular causes and cardiovascular events. Summary: Endothelial progenitor cells can differentiate into endothelial cells and proliferate. They may be candidates for mediating vascular regeneration. These cells, derived from the bone marrow, are thought to support vascular endothelium integrity. Levels of endothelial progenitor cells correlate inversely with cardiovascular risk factors. The authors sought to study the prognostic value associated with circulating endothelial progenitor cells. Endothelial progenitor cells positive for CD-34 and KDR were determined using flow cytometry. Five hundred and nineteen patients with coronary artery disease confirmed by angiography were studied. After twelve months of follow-up, association between death from cardiovascular causes, the occurrence of a first major cardiovascular event (defined as myocardial infarction, hospitalization, revascularization, or death from cardiovascular cause), revascularization, hospitalization, and death from all causes was correlated with baseline levels of endothelial progenitor cells. Two hundred and fourteen patients had a first major cardiovascular event, 43 participants died, with 23 of these deaths from cardiovascular causes. Adjusting for age, vascular risk factors, sex, and other variables relevant to cardiovascular disease, increased levels of endothelial progenitor cells were associated with a reduced risk of a first major cardiovascular event (Hazard ratio (HR) 0.74; 95% confidence interval (CI) 0.62 to 0.89; P ϭ .002), death from cardiovascular causes, (HR 0.31; 95% CI 0.16 to 0.63; P ϭ .001), hospitalization (HR 0.76; 95% CI 0.63 to 0.94; P ϭ .01), and revascularization (HR 0.77; 95% CI 0.62 to 0.95; P ϭ .02). Myocardial infarction and death from all causes were not predicted by endothelial progenitor-cell levels. Comment: The role of endothelial progenitor cells in rejuvenation of vascular endothelium is currently an area of intensive investigation. It appears these immature cells may modify the pathogenesis of atherosclerotic disease. Measurement of endothelial progenitor cells may improve risk stratification in patients with cardiovascular disease.