The characteristics for the ex vivo expansion of the endothelial progenitor cells (EPCs)were explored. CD34+ cells were selected from umbilical cord blood mononuclear cells (MNC) by MiniMACS system, expanded under the same conditions as those for total MNC, coincubation of CD34+ and CD34- from the same donor for EPCs. In addition, the effects of vessel endothelial growth factor (VEGF) and passage on cell differentiation, expansion kinetics and apoptosis were examined.EPCs were determined and quantified by immunocytochemistry and flow cytometry. The results showed that both coculture of CD34+ and CD34 and total MNC led to a significant increase in the expansion of CD34+ cells as compared with CD34 enrichment (P＜0.05). There was a tendency toward decreased apoptosis in cultures when early passage was performed immediately after cord like structures appeared. VEGF had no significant effect on apoptosis (P＞0.05). These differentiated EPCs were positive for CD34+, von Willebrand factor (vWF), KDR, CD31 staining and phagocytized acetylated low-density lipoprotein (LDL). CD34+ cells accounted for (68.2±6.3) % of attaching (AT)cells at day 7 of culture. It was suggested the most efficient method to ex vivo expansion of EPCs was coculture of CD34+ and CD34- or total MNC. Early passage makes cell apoptosis rate decrease.VEGF had no significant effect on ex vivo expansion of EPCs.