Helicobacter pylori (HP) plays a crucial role in gastric carcinogenesis. Few studies have looked at the relationship between HP and Barrett's esophagus/cancer. To further investigate this, a study comparing the prevalence of HP and increasing grades of dysplasia was undertaken. Biopsies from 19 malignant and 94 benign cases of Barrett's esophagus were analysed histologically for the presence of HP. 34% of non-dysplastic Barrett's epithelium was colonized with HP compared with only 17% of dysplastic/malignant cases (P = 0.04). No relationship was found between HP status and: (i) length of Barrett's esophagus; (ii) the presence of ulcers or strictures; and (iii) previous anti-reflux surgery. HP colonization of Barrett's esophagus is not uncommon. We found that HP has a negative correlation with increasing dysplasia which is analogous to gastric carcinogenesis. This finding should be investigated in prospective studies to elucidate its role in Barrett's adenocarcinoma.