Antidiabetic treatment with an extract of Portulaca oleracea leaves (100mg/kg and 250mg/kg body weight) for three weeks showed a significant reduction in thiobarbituric acid reactive substances (TBRAS) and an increase in glutathione reductase (GSH-R) in both the liver and kidney of STZ diabetic rats. The treatment with P. oleracea significantly altered the glutathione and GSH-R to be comparable with the control group. P. oleracea- and tolbutamide-treated rats showed decreased lipid peroxidation that is associated with increased activity of superoxide dismutase (SOD) and catalase(CAT). The effects of P. oleracea on tissue lipid peroxidation and antioxidant status in diabetic animals have not been studied before. The result of this study thus shows that although P. oleracea extract possesses moderate antidiabetic activity, it exhibits potent antioxidant potential in diabetic conditions. Copyright ©2009 The Berkeley Electronic Press. All rights reserved.