Helicobacter pylori infections of the gastric mucosa are common among elderly adults, particularly in developing countries. It has now been proven that in nearly all cases of gastric ulcer the bacterium plays a role. Moreover, the adenocarcinoma of the stomach which occurs frequently in poor countries, develops mostly in connection with H.pylori infections. Nevertheless, more is needed than just this bacterium, for the majority of the infected never develop gastric carcinoma. The diagnosis of bacterial infection of the stomach can be made with endoscopical biopsy material but also with non-invasive methods. The infection can be treated with combinations of antibiotics after which the patient is completely cured in most of the cases.