Chronic inflammation in the stomach caused by Helicobacter pylori is an important factor in the development of peptic and duodenal ulcer disease, and gastric malignancies. Research aims to improve the understanding on long-term survival and adaptation of H. pylori, on the pathogenesis of chronic H. pylori infections, and on improved diagnostics and treatment of H. pylori infection. In addition to H. pylori, increasing attention is given to non-pylori Helicobacter species. Reflux-induced chronic inflammation is thought to be initiating factor of the development of Barrett's esophagus, a precursor of adenocarcinoma of the gastro-esophageal junction. This hypothesis is being tested both in patients, animal model systems as well as in vitro. Finally, the putative role of non-pylori Helicobacter spp. in nongastric pathologies such as hepatocellular carcinoma and Inflammatory Bowel Disease is being investigated.