The treatment of duodenal ulcer has evolved from ineffective medical treatments through an era of surgical management, back to increasingly effective medical treatment. The advent of H2-receptor antagonists changed the outlook for ulcer patients. More recently, Helicobacter pylori, an organism which inhabits gastric mucosa exclusively, has been implicated in the pathogenesis of peptic ulcer. This bacterium is found in the stomachs of around 95% of duodenal ulcer patients. Its eradication is shown dramatically to improve the rate at which ulcers relapse. The mechanisms whereby it may cause ulceration are not established--we review current hypotheses. No method of eradication is 100% effective, and many different dual or triple therapy regimens have been tried. Metronidazole resistance is reported but its importance is not yet known. Helicobacter eradication is likely to prove a cost-effective and acceptable treatment for duodenal ulcer, and once its value has gained acceptance widespread uptake of this option is anticipated.