This work studies the hypoglycemic activity of a decoction from juniper "berries" (Juniperus communis) both in normoglycemic and in streptozotocin-diabetic animals. Juniper decoction decreases glycemic levels in normoglycemic rats at a dose of 250 mg/kg. This effect can be achieved through: a) an increase of peripheral glucose consumption; b) a potentiation of glucose-induced insulin secretion. The administration of the decoction (125 mg total "berries"/kg) to streptozotocin-diabetic rats for 24 days results in a significant reduction both in blood glucose levels and in the mortality index, as well as the prevention of the loss of body weight. This effect seems to be mediated by the peripheral action of juniper.