In this study, we investigated the antioxidative effects of So-Dang-Tang (SDT) on streptozotocin (STZ)-induced diabetic rats. Diabetes was induced by intraperitoneal injection of STZ (45 mg/kg body weight) into Sprague-Dawley rats. The SDT (200 mg/kg) and the reference drug, glibenclimide (1mg/kg), were orally administered once a day for 28 days in STZ-induced diabetic rats. The activity of antioxidant enzymes, including those of superoxide dismutase (SOD) and catalase, and the levels of glutathione (GSH) and production of malondialdehyde (MDA) were measured in the liver, kidney, and pancreas of diabetic rats. Treatment with SDT in STZ-induced diabetic rats significantly increased the activities of antioxidant enzymes and GSH levels in the liver, kidney, and pancreas when compared to those of the STZ-control group. SDT also significantly decreased lipid peroxidation product and MDA levels in STZ-induced diabetic rats. These results indicate that SDT has an antioxidative action in STZ-induced diabetic rats.