This study evaluated the gastroprotective activity of DA-6034 against various ulcerogens including ethanol, aspirin, indomethacin, stress, and acetic acid. The basic mechanisms of DA-6034 as a defensive factor such as mucus secretion and endogenous prostaglandin E(2) synthesis were determined. Rats with gastric lesions induced by ethanol-HCl, aspirin, indomethacin, and stress that had been pretreated with DA-6034 orally showed a statistically significant decrease or decreasing tendency of the gastric lesion. In acetic acid-induced gastric lesions, repeated oral administration of DA-6034 exhibited a U-shape activity in ulcer healing, with the maximum and minimum inhibition being observed at 30 and 10 mg/kg/day, respectively. DA-6034 also increased the mucus content in the gel layer as well as endogenous prostaglandin E(2) synthesis. These results suggest that DA-6034 prevents gastric mucosal injury, and these gastroprotective activities appear to be due to the increase in the gastric defensive systems.