To test the hypothesis that a mobilization of endothelial progenitor cells (EPCs) occurs after acute cerebrovascular diseases, we evaluated the number of EPCs in the process of acute stroke. A total of 203 individuals were examined, including 100 patients with ischemic strokes, 36 patients with hemorrhagic strokes and 67 healthy controls. Ninety-eight patients were observed at days 1, 7, 14 and 28 after acute stroke. Circulating EPCs were defined by the surface markers CD133/KDR and analyzed by flow cytometry. Serum high sensitivity C-reactive protein (hs-CRP) concentrations were determined by particle-enhanced immunonephelometry using the N high sensitivity CRP Reagent. Patients with acute stroke had lower numbers of EPCs (0.037+/-0.001/100 peripheral blood mononuclear cells (PMNCs) vs. 0.06+/-0.002/100 PMNCs, P<0.05) and higher levels of serum hs-CRP (1.99 vs. 0.03 mg per 100 ml, P<0.05) than control subjects after adjusting for age, sex, body mass index (BMI) and blood pressure. There were no differences in EPCs counts or serum hs-CRP levels between patients with ischemic and hemorrhagic stroke. In univariate analyses, BMI, age, systolic blood pressure (SBP), diastolic blood pressure, low-density lipoprotein (LDL), total cholesterol (T-cho), blood glucose and hs-CRP (P<0.001) were inversely correlated with EPCs counts. Multivariate analyses showed SBP and total cholesterol as independent predictors of EPCs levels. The number of EPCs gradually increased at day 7 after acute onset, remained elevated at day 14; and returned to baseline by day 28. Our results suggest a possible contribution of circulating EPCs in acute stroke. SBP and total cholesterol are independent factors of reduced EPCs numbers. A transient early increment of EPCs may result from the mobilization of EPCs in response to stroke stress.