Aim To observe the role that stromal cell derived factor-1α(SDF-1α) plays in the biological functions of endothelial outgrowth cell(EOC),and the effect that rapamycin exerts on such role.Methods The mononuclear cells were harvested from umbilical cord blood by Ficoll density gradient centrifugation,induced into EOC and then expanded in vitro.The endothelial progenitor characteristics of second generation EOC were identified by immunostaining staining.The third generation EOC were devided into 4 groups,which were treated with 10 μg/L SDF-1α,10 μg/L SDF-1α+1 μg/L rapamycin,1 μg/L rapamycin and blank culture medium for 24 hours respectively.Proliferative capacity was measured by CCK-8 assay,and the migrational ability of the EOC was analysed by scarification test.Results EOC possessed many endothelial characteristics.Immunostaining showed that surface antigens factor Ⅷ,CD34 and Flk-1 were postive.The proliferative capacity and the migrational ability of the EOC were both enhanced after incubation with the 10 μg/L SDF-1α(P<0.01).While 1 μg/L rapamycin not only counteracted such effect(P<0.01),but also inhibited the biological functions of the EOC(P<0.05).Conclusoins SDF-1α can activate the proliferative capacity and the migrational ability of EOC.Rapamycin not only counteracts such effect,but also inhibits the biological functions of the EOC directly.