One half of the world's population has Helicobacter pylori infection, with an estimated prevalence of 30 percent in North America. Although it is unclear whether eradication of H. pylori improves symptoms in patients with nonulcer dyspepsia, there is strong evidence that eradication of this bacteria improves healing and reduces the risk of recurrence or rebleeding in patients with duodenal or gastric ulcer. A "test-and-treat" strategy is recommended for most patients with undifferentiated dyspepsia. With this approach, patients undergo a noninvasive test for H. pylori infection and, if positive, are treated with eradication therapy. This strategy reduces the need for antisecretory medications as well as the number of endoscopies. The urea breath test or stool antigen test is recommended. Until recently, the recommended duration of therapy for H. pylori eradication was 10 to 14 days. Shorter courses of treatment (i.e., one to five days) have demonstrated eradication rates of 89 to 95 percent with the potential for greater patient compliance. A one-day treatment course consists of bismuth subsalicylate, amoxicillin, and metronidazole, all given four times with a one-time dose of lansoprazole. In children with documented H. pylori infection, however, all regimens should continue to be prescribed for seven to 14 days until short-course treatment is studied and its effectiveness has been established in this population.