In 1983, the presence of Helicobacter PyIori (HP), in the gastric mucus of biopsy from patients with Peptic Ulcer Disease (PUD), was described. A lot of articles had been published about this subject since then. Most links between this bacillus and the upper gastrointestinal pathology has been with gastritis type B and Duodenal Ulcer (DU). By now, we still do not know very much about this subject, but we cannot deny the great horizons created for this find, towards the understanding of the gastro duodenal disease. HP is assumed by a lot of Investigators as one of the most important factors for balance of aggressive and protector mechanisms of the gastro duodenal mucus, although it is not completely know how the balance of this mechanism are disturbed. This article makes a review of a little part of the wide development obtained for HP in the last years. It is physiopathology, epidemiology, diagnostic and treatment.