Objective To detect the expression of CD31 and SSEA-1 at different stages of developing embryos,as well as their expressions in neonates,adult bone marrow and testis.Methods 129/SV mice were mated.Embryos at 10.5 postcoitus（E10.5）,14.5 and 18.5 days were collected.In addition,neonatal mice,bone marrow and testis from 6-week-old mice were also collected.Single cell suspension was achieved by digestion with collagenase.After anti-CD31 and anti-SSEA-1 antibody labeling,cells were analyzed by flow cytometry.Results CD31 and SSEA-1 were expressed in E10.5,E14.5 and E18.5.The expression levels were decreased with the development of embryos.Meanwhile,both markers were observed in neonates,adult bone marrow and testis,but the level was lower than in embryos.Conclusion A certain amount of CD31 and SSEA-1 expressing cells are existing in developing embryos as well as in adult tissues.