Forty-five patients with bile reflux at endoscopic examination, confirmed by titration of bile acids in gastric juice, were admitted to the study and divided into three groups in accordance with histologic results: normal findings, chronic superficial gastritis, and chronic atrophic gastritis. Bile acid pattern was determined in duodenal samples by high-performance liquid chromatography titration, and the mucoprotein content of gastric juice was assessed. The results of qualitative analysis of bile acid showed an increase of deoxycholic acid in patients with atrophic gastritis (p less than 0.05) in comparison with controls; determination of taurine and glycine conjugates showed an increase of taurodeoxycholic acid in patients with atrophic gastritis (p less than 0.01) compared with controls. The composition of mucus was altered only in patients with atrophic gastritis. Whether the increase in deoxycholic acid in biliary reflux is a factor in the development of chronic atrophic gastritis or is secondary to the increase of gastric pH, detectable in this condition, is still uncertain. However, the increase of deoxycholic acid and its taurine conjugates may be a factor that leads to persistence of mucosal lesions.