The exposure of gastric mucosa to ethanol produces acute ulcers mediated by inflammatory processes, hemorrhagic erosions and increase of reactive oxygen species. The purpose of this study was to assess the effects of Coptidis Rhizoma(CR) aqueous extracts on hydrochloride (HCl)/ethanol induced gastric ulcer in mice as compared with rebamipide (30 mg/kg) and ranitidine (100 mg/kg). Stomach ulcers were induced by oral ingestion of HCl/ethanol. CR extracts (125, 250 and 500 mg/kg) were orally administered, once a day for 7 continuous days, and 1 hr after last 7th treatment of CR extracts stomach ulcers were induced. Effects of CR extracts on HCl/ethanol-induced gastric ulcer were evaluated based on gross and microscopic observations with anti-oxidant activities. All three different dosages of CR extract significantly decreased HCl/ethanol-induced gastric ulcer compared with the HCl/ethanol control mice. CR extracts also strengthened the antioxidative defense systems - decreased the level of lipid peroxidation but increased the level of catalase, superoxide dismutase and nitrate/nitrite compared with the HCl/ethanol control. The effects of CR extract 500 mg/kg were similar to that of 30 mg/kg rebamipide, and CR extract 250 mg/kg showed similar anti-ulcer effects as compared with ranitidine 100 mg/kg. These results suggest that the gastroprotective effects of CR extracts on mice ulcer models can be attributed to its ameliorating effect on oxidative damages.