In Chang liver cells the administration of oxytocin and vasopressin as well as the combined application of the two hormones will result in a positive binding imprinting for oxytocin and a negative binding imprinting for vasopressin. The hormones are able to increase the mitotic capacity of the liver cells even without previous imprinting, both in the case of treatment for 4 hours and for 24 hours; the change, however, is more marked in the case of treatment for 4 hours. Treatment for 24 hours results also in some functional imprinting.