We investigated the effects of ecabet sodium on experimentally induced reflux esophagitis in rats. Three groups of rats, i.e., a control group, esophagitis group, and an ecabet sodium group (25mg/kg given twice daily) were used. The number of animals which developed esophagitis, the extent of the lesions, and the esophagitis lesion index were assessed 3 weeks after the start of the experiment, and the lesions were evaluated histopathologically. All nine surviving rats in the esophagitis group developed esophagitis, and the esophagitis lesion index was 32.6 +/- 7.2 (mean +/- SE) per animal. Histopathologically, thickening of the epithelium, elongation of papillae of the lamina propria into the epithelium, and infiltration of the lamina propria by lymphocytes, eosinophils, plasmacytes, and neutrophils, were observed. Interruption of the lamina of the muscularis mucosae was also observed, and there was marked proliferation of collagen fibers in the submucosa and lamina propria. In the ecabet sodium group, esophagitis developed in five of the nine surviving animals (55.6%), but the esophagitis lesion index was 1.89 +/- 0.73 per animal, which was significantly lower than that in the esophagitis group. The histopathological changes in the rats which developed esophagitis were milder in the ecabet sodium group than in the esophagitis group. These results suggest that ecabet sodium could be useful for the prevention of reflux esophagitis.