Dyspepsia is a poorly understood term that is used to describe symptoms that originate in the upper gastrointestinal tract. There is increasing evidence that Helicobacter pylori infection plays an aetiological role in some forms of dyspepsia. H. pylori infection is more common in dyspeptic patients than asymptomatic controls. Clinical trials of the benefit of H. pylori eradication therapy in non-ulcer dyspepsia have given conflicting results. This may be due to methodological flaws in the studies to date. Trials in non-ulcer dyspepsia may have several end-points. Future studies should be long-term, placebo-controlled, double-blind, and use a validated symptom questionnaire. Acid secretion studies demonstrate acid hypersecretion in non-ulcer dyspepsia that is intermediate between that seen in duodenal ulcers and asymptomatic carriers. This suggests that H. pylori gastritis represents a spectrum of disease that includes duodenal ulceration, whose natural history is one of relapses and remissions, and non-ulcer dyspepsia.