SUMMARY: A method is described for reducing the maintenance of frogs used for the diagnosis of pregnancy by enforced hibernation. Fifty males (Rana esculenta) were stored in a domestic refrigerator; twenty were removed at the end of 5 months, and thirty at the end of 7 months, and all survived and were healthy. Examination of the frogs' urine after injection of 1 ml. of untreated pregnancy urine, known to contain between 8 and 16 i.u. of chorionic gonadotrophin, showed that all fifty animals shed uncountable numbers of sperm. It is suggested that in addition to the use of these animals for pregnancy work, they are always available for dissection and physiological experiments.