Blood glucose and total lipid levels in rats with streptozotocin-induced diabetes were determined after intraperitoneal administration of a methanolic extract of Prunus davidiana Fr. stems and its main component, prunin (= naringenin 7-O-beta-D-glucoside). From the data obtained it was concluded that intraperitoneal administration of the methanolic extract and prunin produced a significant hypoglycemic effect. Total blood lipids were also decreased by these substances. Thus, it is suggested that this methanolic extract contains one or more hypoglycemic principles including the main flavanone glycoside, prunin, which can significantly reduce the levels of blood glucose and total lipids in streptozotocin-diabetic rats.