Intragastric bile acids on fasting for 1 hour have been determined by radioimmunoassay and thin-layer chromatographic scanning in 102 cases of chronic gastritis. The results showed that all of intragastric conjunction bile acids were higher in chronic atrophic gastritis group than those in chronic superficial gastritis group. Both of their intragastric bile acids and nitrite levels increased significantly in patients whose gastric mucosa appeared acute inflammation, glandular atrophy and moderate or severe intestinal metaplasia. These findings suggest that bile acids may be implicated in premalignant histological changes of gastric mucosa such as chronic atrophic gastritis. Determining intragastric bile acids will reflect the degree and injurious effect of duodenogastric reflux.