In oriental medicine, Artemisiae asiatica (AA) has been used as analgesic, antiinflammatory agent, and coagulatory agent. Furthermore, eupatilin, a kind of flavonoids, is known as the active principle component of AA. This study was undertaken to determine the gastric antiulceration of AA and to elucidate its mechanism. AA showed the inhibitory effect on gastric ulceration induced by EtOH/HCl and aspirin. To elucidate its mechanism, the effect of AA on lipidperoxide level in gastric mucosa, microsome lipidperoxidation, iron -dependent lipidperoxidation, and neutrophil activation were examined. It is suggested that the antiperoxidative and antineutrophil activity of AA play important roles as a possible mechanism. These results suggest that AA might have gastric antiulceration activity due to antilipidperoxdative and antineutrophil activity.