In the world of modern medicine it is rare that the understanding of a previously described clinical disease is so completely revolutionized that clinical textbooks must be rewritten. This, however, has been the outcome of the isolation ofHelicobacter pylori from the human stomach. Only 15 years after its initial isolation, this bacterium has been proven to be the etiological agent of acute on chronic gastritis, and a predisposing factor in peptic ulcer disease, gastric carcinoma and B cell mucosa-associated lymphoid tissue (MALT) lymphoma (Graham et al. 1992; IARC 1994; Marshall et al. 1985; Parsonnet et al. 1994).