DNA was extracted from the gastric mucosa of 69 patients and analysed for the presence of DNA adducts by 32P-postlabelling. Adduct levels found in patients with histologically normal gastric mucosa were compared with levels found in patients displaying evidence of chronic atrophic gastritis or intestinal metaplasia, both of which may be considered pre-malignant conditions. Adduct patterns were the same for all patients, but the highest adduct levels were found in the latter two groups. Mean adduct levels were also higher in patients with abnormal gastric mucosa, but there was no statistically significant difference in adduct levels between the normal and pre-malignant groups (P > 0.05, Mann-Whitney U test). Thus DNA adduct levels do not correlate with the presence of histological abnormalities in the stomach and are not useful as a marker of malignant potential.