Total and individual bile acid concentrations in the oesophageal aspirates from 30 patients with Barrett's oesophagus were compared with those from 15 patients with oesophagitis and 15 normal subjects. The highest total bile acid concentrations were found in the Barrett's patients and this was statistically significant when compared with controls but not oesophagitis patients. However, when the 95th percentile value of bile acid concentration in the normal subjects was taken as the 'cut-off' level, a significantly higher number of Barrett's patients (15/30) were bile refluxers than were the oesophagitis patients (3/15). Glycocholic and taurocholic acids were the predominant bile acids detected, but taurochenodeoxycholic acid was also present in significant amounts in the patients with oesophagitis. It is possible that bile reflux contributes to the development of Barrett's oesophagus.