Анотация: The aim of the study was to determine the relationship between the rate of cooling of eight-cell mouse embryos to the temperature of liquid nitrogen (-196 C) and their developmental capacity after thawing on the basis of their ability to leave the zona pellucida (` hatching `) during in vitro culturing. Eight-cell embryos were obtained from superovulated female mice and divided into three experimental and one control group. Embryos from the experimental groups were cryopreserved by the vitrification method using ethylene glycol as cryoprotectant. The vitrification protocols used in the study differed in the rate of cooling of the cryoprotectant solution