This chapter discusses Helicobacter pylori, a gram-negative spiral-shaped bacteria that infects more than 50% of humans globally. H. pylori infection is a serious, chronic, transmissible infectious disease that causes progressive, destructive inflammation of the stomach and is etiologically related to a number of important diseases, including gastric and duodenal ulcer disease, gastric cancer, primary B-cell gastric lymphoma, and atrophic gastritis. This chapter explores the prevalence of H. pylori infection that is inversely related to the general health, well-being, and degree of development of a society. It investigates the acquisition of H. pylori infection, which is often associated with transient symptoms.