In clinical and experimental conditions, a biochemical equipment and a histological image of a fresh embryonic nervous tissue and a tissue conserved by deep freezing for transplantation purposes were examined. By repeated examination of neurotransmitters, the contents of dopamine and serotonin were found unchanged by freezing. In a human embryo, serotonin predominates over dopamine, while in chicken embryos, used for xeno-transplantations, it is vice versa. As for the microscopic structure of nervous tissue, no influence of kryopreservation for 4 to 14 days was found.