Helicobacter pylori has been associated with chronic type-B gastritis, which in turn is always present in duodenal ulcer patients; therefore, it is likely that Helicobacter pylori is an important cofactor in the pathogenesis of peptic ulcer disease. An eradication of Helicobacter pylori is associated with the reduced ulcer relapse rate, but an effective therapy for eradication is not yet available and should be restricted to experimental protocols. 2. Omeprazole is an antagonist of the proton pump of the acid-producing cell of the human stomach. With once-daily omeprazole treatment it is possible to almost abolish 24-hour intragastric acidity in the majority of duodenal ulcer patients; therefore, omeprazole allows alternative treatment of different causes of peptic disease.