Barrett's oesophagus is an acquired precancerous condition that develops from mucosal injury incurred due to chronic gastro-oesophageal reflux. The aim of this study was to determine if bile and/or acid components of the refluxate can induce DNA damage in vitro. The oesophageal cell lines FLO-1 and HET1-A were exposed to primary bile salts, individually or as a mixture, and the secondary bile salt sodium deoxycholate, in neutral or acidified media. Cells were then examined in the comet assay to measure DNA strand breaks. Cell viability was also monitored. Acidified media induced DNA damage in a pH- and time-dependent manner. The primary bile compounds sodium glycocholate, glycocholic acid, sodium taurocholate and taurochenodeoxycholate, as an equimolar mixture (100 microM), caused a small but significant (P < 0.028) elevation in DNA damage, but only at neutral pH in FLO-1 cells. Sodium deoxycholate (100 microM) caused a significant (P < 0.008) elevation in DNA damage in both cell lines, but again only at neutral pH. These data suggest that specific components of gastro-oesophageal refluxate are capable of causing DNA damage and may participate in the genesis and progression of Barrett's oesophagus via this mechanism.