Campylobacter pylori is an organism living under mucus layer in the stomach and on the places of gastric mucosa metaplasia. It is known to be responsible for the development of gastritis, probably also it participates in the pathogenesis of dyspepsia without ulcer, while its role in the development of gastric and duodenal ulcer has not yet been explained completely. The authors present a characteristics of the organism and the methods of its detection. A number of investigations are discussed which demonstrate its clinical importance. In summary, it is shown that the present state of knowledge on Campylobacter pylori is insufficient for serving as a rationale for antibacterial treatment of peptic ulcer.