Aim To investigate the effect of cryopreservation on the proliferative abilitiy and vasculogenesis activity of endothelial outgrowth cells(EOC),and to explore the possibility of its resuscitation.Methods The mononuclear cells were harvested from umbilical cord blood by density gradient centrifugation,induced into EOC and expanded in vitro.The endothelial characteristics of EOC were identified by immunostaining and fluorescent staining.Then EOC were cryopreserved at-20℃ for 4 h,-75℃ overnight and then cryopreserved into liquid nitrogen using culture medium containing 50 mL/L and 80 mL/L dimethyl sulfoxide(DMSO).After 24 h cryopreserved EOC were resuscitated,and the resuscitative rate,proliferative ability and vasculogenesis activity were measured.Results EOC possessed many endothelial characteristics.Immunostaining showed that surface antigens Factor Ⅷ,CD34 and Flk-1 were postive;and fluorescent staining experiment revealed that EOC both bound to FITC-UEA-1 and uptook DiI-ac-LDL.There were no statistical differences between 50 mL/L and 80 mL/L DMSO group in resuscitative rate(79%±6% vs 88%±4%,p>0.05).During early period after resuscitation(within 36 h),two cryopreservated groups(50 mL/L and 80 mL/L DMSO group) both showed decrease in proliferative abilitiy compared with non-cryopreservated group(p<0.05).72 h later there were no significant differences between 50 mL/L,80 mL/L DMSO group and non-cryopreservated group in the proliferative ability(p>0.05).In contrast,vasculogenesis activity analysis revealed attenuation in vasculogenesis activity within 6 h(p<0.05) while 30 h later such attenuation became insignificant(p>0.05).Conclusions EOC can be cryopreservated and resuscitated.The cryopreservated cell shows no significant decrease in proliferative abilitiy and vasculogenesis activity after resuscitation.