Objectives : The purpose of this study is to evaluate whether or not a pretreatment with Portulaca oleracea has an antioxidant effect in HCl-ethanol induced gastric mucosal damage. Methods : We elucidated the level of reactive oxygen species (ROS), lipid peroxidation, and two important constituents of antioxidant defense such as superoxide dismutase (SOD), glutathione (GSH) in these effects. Results : The oral administration of crude extract from P. oleracea attenuated the gastritic lesion area, submucosal edema and hemorrhage, and mucosal necrosis induced by HCl-ethanol. The MDA levels of control group were higher than those in the rats given the P. oleracea pretreatment. While the GSH levels of control were decreased, the GSH activity on the gastric mucosal layer maintain normal level in rats given the Portulaca oleracea pretreatment before HCl-ethanol induced gastritis significantly increased. However, the SOD activites were not altered by P. oleracea. Conclusions : The administration of Portulaca oleracea have a protective antioxidant effect against the gastric lesion induced by HCl-ethanol and may therefore be a promising drug for gastritis and gastric ulcer.