In 1982, Helicobacter pylori was isolated from the human stomach for the first time. 64 Since then, it has garnered considerable interest. In 1996, according to one computer database, more papers were published on H. pylori than on any other enteric pathogen. At the 1997 United States Gastroenterology Conference (Digestive Diseases Week), more than 500 presentations related to clinical, epidemiologic, pathophysiologic or microbiologic aspects of this organism. The emergence of H. pylori into clinical consciousness, however, belies what is happening to the organism itself. Epidemiologic studies indicate that H. pylori infection is decreasing in prevalence, at least in the industrialized West. Moreover, the diseases attributed to H. pylori infection, peptic ulcer disease and gastric malignancy, are declining in parallel with infection; however, despite these decreases, H. pylori remains an important cause of morbidity and mortality throughout the world. Peptic ulcer disease continues to affect millions annually, and gastric cancer is among the top few causes of cancer death worldwide. Thus, the extraordinary attention devoted to this curable and perhaps preventable infection appears well warranted.