Objective : Diabetes is a disease in which the body does not produce or properly use insulin. Etiological studies of diabetes and its complications showed that oxidative stress might playa major role. Therefore, many efforts have been made to regulate oxygen free radicals for treating diabetes and its complications. Because Jindangwon has been known to be effective in treatment of diabetes, the methanol extract of Jindangwon was tested for its effectiveness in reducing the oxidative stress induced by Streptozotocin. Methods : Jindangwon was washed, dried in the shade and crushed. The crushed Jindangwon was extracted 3 times, each time with 3 volumes of methyl alcohol at $60^{circ}C$ for 24 hours. The extract was filtered and evaporated under reduced pressure using a rotary evaporator to yield 30.6 g. Jindangwon extract was oral-administered to the diabetic rats induced by streptozotocin 50 mg per 1 kg of body weight for 15 days. The efficacy of the Jindangwon extract was examined with regard to the enzymatic pathways involved in the oxygen free radical production and the glutathione balance. Results : he effects of the methanol extract of Jindangwon in streptozotocin-induced diabetics rats with regard to body weight, blood glucose level, hepatic lipid peroxide level, hepatic xanthine oxidase activity and type conversion rate, hepatic glutathione level, hepatic glutathione peroxidase activity, hepatic glutathione reductase activity, hepatic aldose reductase activity, and hepatic sorbitol dehydrogenase activity were favorable enough to suggest that it is a cure for diabetes and its complications. Conclusions :These results support Jindangwon as an effective reducing agent for oxidative stress in the tissues and organs by regulating the production of oxygen free radicals. Jindangwon, in particular, shows promising results for its use as a cure, or preventative medicine for diabetes and its complications by reducing oxidative stress in beta-cells of the pancreas.