The discovery and concept that Helicobacter pylori is associated with gastric disease including gastric cancer which is one of the most common and frequently lethal forms of malignancy, heralded a new and rapidly expanding field recognizing the emergence of many new pathogens and disease syndromes in clinical medicine, as well as basic infectious disease research. There is now an extensive and widely known literature of how H. pylori is involved in a wide variety of disease syn dromes. As summarized in the introductory chapter of this volume, many major advances have been made in diagnosis, both serologic and endoscopic in time of the involvement of this organism in patients with upper GI ailments as well as its presence in those who are not clinically ill. The Introduction describes the rapid development of understanding the role of this organism in disease. The basic bacteriology of H. pylori is then described in the second chapter. Diagnostic tests for detecting H. pylori infection is then highlighted, as well as the role of such infection in gastric cancer. Current knowledge concerning risk factors and peptic ulcer pathology associated with H. pylori is then described. Newer information concerning therapy of H. pylori infection and colonization is described in a subsequent chapter as well as one concerning the effects of anti biotics on H. pylori infection. The extensive literature on natural substances with anti-H.