Multiple gastric biopsies and gastric juice aspirates were taken in 108 patients undergoing routine or review gastroscopy for a variety of upper gastrointestinal disorders. The gastric juice was measured for free and total bile acids and the biopsies examined for premalignant mucosal changes. Total bile acid levels were significantly higher in patients with atrophic gastritis, intestinal metaplasia and dysplasia but not chronic gastritis. There was no correlation between the severity of the dysplasia and total bile acid levels. Free bile acid levels were significantly higher in patients with atrophic gastritis but not in patients with chronic gastritis, intestinal metaplasia or dysplasia. These results suggest that intragastric bile acids may be implicated in premalignant histological changes of gastric mucosa and thus play a part in gastric carcinogenesis.