Helicobacter pylori, the most common source of chronic infection worldwide, is a principal aetiological agent of type B gastritis, gastric and duodenal ulcers, and mucosa-associated lymphoid tissue lymphomas; the presence of this pathogen is also associated with gastric carcinoma, Infection with H. pylori is prevalent in patients with gastrooesophageal reflux disease (GORD) even though it does not appear to play an important role in GORD pathophysiology, However, epidemiological studies have shown that colonization with cagA-positive H. pylori provides significant protection against the development of GORD and its long-term complications. Whereas clinical trial results indicate that the presence of H. pylori has little influence on the effectiveness of antisecretory therapy with a proton pump inhibitor (PPI) in patients with GORD, the metaanalysis of results from long-term studies suggests that risk of GORD relapse may be reduced in the presence of H. pylori infection. Several investigators have raised concerns about increased risk for gastric neoplasia in H,pylori-positive patients treated with PPIs. However, long-term follow-up of such patients indicates neither significant risk of neoplasia nor accelerated development of gastric glandular atrophy. Thus, the excellent safety record of these compounds seems not to be compromised by the presence of H. pylori. Eur J Gastroenterol Hepafol 13 (suppl 1):S23-S27 (C) 2001 Lippincott Williams & Wilkins.