The effects of extract mixture of red ginseng and steamed Rehmaniae radix prepared for antidiabetic activity was examined in streptozotocin-Induced diabetic rats. The increased blood glucosec level in the streptozotocin-induced diabetic rats was significantly decreased by the treatment with the mixture (800, 1600 mg/kg, p.o.). However, neither red ginseng extract nor steamed Rehmaniae radix extract alone showed significant hypoglycemic effects. The mixture prevented a weight loss in streptozotocin-induced diabetic rats. These results suggest that the mixture has the relieving action against streptozotocin-induced hyperglycemia.