Since some complications of diabetes mellitus may be caused or exacerbated by an oxidative stress, the protective effects of (1) a garlic (Allium sativum) aqueous extract or (2) a combination of α-tocopherol and magnesium were investigated comparatively in alloxan-diabetic rats. Garlic extract (1 mL of extract corresponding to 300 mg fresh garlic/kg) or α-tocopherol (100 mg/kg) + MgCl(2) (200 mg/kg body weight) were i.p. injected to rats, once a day for 4 weeks. Lipid peroxidation levels and the activities of superoxide-dismutase, catalase and glutathione peroxidase were then measured in liver and pancreas. Under our experimental conditions, garlic extract or α-tocopherol + Mg were found to (1) significantly reduce the plasma levels of glucose, total cholesterol and triglyceride and (2) lactate dehydrogenase, alkaline phosphatase and transaminase activities in blood of diabetic animals. In addition, treatment with garlic extract or α-tocopherol + magnesium appeared to exert an antioxidative activity demonstrated (1) by the increase of catalase, superoxide-dismutase and glutathione-peroxidase activities in liver and pancreas, and (2) a lowering of lipid peroxidation level in these organs. In conclusion, both garlic extract and α-tocopherol + magnesium association were found to alleviate diabetes-associated metabolic disorders and oxidative stress in rats.