To forsee appropriate developmental cell stage in human embryos for cryopreservation, we observed blastocyst development in culture medium after cryopreservatlon and thawing of one cell, two cell, four cell stage of mice embryos. According to our results, development of the blastocyst of cryopreserved two cell mice embryos was significantly higher than that of cryopreserved one cell mice zygotes or four cell mice embryos.