Helicobacter pylori is associated with chronic peptic ulcer disease. The high prevalence of H. pylori infection tends to decrease in Western countries suggesting that the incidence of gastroduodenal ulcers not related to antiinflammatory drugs will fall. Abundant data support the leading role of H. pylori in peptic disease through dysregulation of acid production, induction of gastric metaplasia, and development of chronic gastritis. Endoscopy is the key to diagnosis, allowing direct assessment of H. pylori infection. H. pylori eradication is the major aim of peptic ulcer treatment, dramatically improving the recurrence of ulcers, although its efficiency should be controlled in various clinical situations.