Fasting and postprandial intragastric bile acid concentrations have been estimated and compared in patients with complications of Barrett's oesophagus, patients with Barrett's oesophagus without complications, patients with oesophagitis and a group of normal subjects who acted as controls. There was no significant difference in fasting intragastric bile acid concentrations between the groups. Postprandial bile acid concentrations were significantly greater in the patients with complications of Barrett's than in the remaining groups at 60, 90 and 120 min. Significant concentrations of bile acids were seen in gastric juice of unaltered pH and may be undetected on intra-oesophageal pH monitoring. Duodenogastric reflux may be implicated in the pathogenesis of complications of Barrett's oesophagus.