Indomethacin is a nonsteroid anti-inflammatory agent that is known to induce severe gastric mucosal lesions. In this study, we investigated the effect of selenium on gastric mucosal lesions in rats. To confirm the curative effect of selenium against indomethacin-induced gastric ulcers, gastric ulcers were induced by oral administration of 25 mg/kg indomethacin, and then different doses (10, 50, and 100 microgram/kg of body weight) of selenium or vehicle were treated by oral gavage for 3 days. Oral administration of indomethacin clearly increased the gastric ulcer area in the stomach, whereas selenium applied for 3 days significantly decreased the gastric ulcer area in a dose-dependent manner. In addition, selenium markedly reduced the increase of lipid peroxidation induced by indomethacin in the gastric mucosa and increased activities of radical scavenging enzymes such as superoxide dismutase, catalase, and glutathione peroxidase in a dose-dependent manner. These results reveal that selenium can heal indomethacininduced gastric ulcers through elimination of the lipid peroxides and activation of radical scavenging enzymes.