Helicobacter pylori infection affects approximately half of the world's population. In Hong Kong, approximately 55% of the population is infected with this organism. But symptoms and clinical disease develop in only a minority of infected individuals during their lifetime. Treatment should thus be appropriately targeted. It is imperative that infected patients who have either a current or past history of peptic ulcer disease, with or without bleeding or a perforation complication, and those with low-grade gastric, mucosal-associated lymphoid tissue lymphoma should all have the organism eliminated. There is evidence that anti-Helicobacter pylori therapy reduces the recurrence of gastric cancer after the successful removal of early gastric cancer lesions. Patients with non-ulcer dyspepsia, particularly those with severe symptoms, should also be considered for a trial of eradication therapy. Whether or not eradication therapy should be given to those who require long-term non-steroidal anti-inflammatory drug therapy, but who do not have a history of peptic ulcer disease is still not decided. The use of prophylactic eradication to stop the development of gastric cancer or peptic ulceration in H pylori--positive but asymptomatic individuals should be considered only in research settings.