A major role for Helicobacter pylori gastritis in nonulcer dyspepsia (NUD) is controversial. Gastroduodenal dysfunction may be associated with H. pylori infection, but there is little evidence for a causal link with dyspepsia. Population-based studies with appropriate methodology have generally failed to confirm an association between H. pylori and NUD. Furthermore, no definite association between subgroups of NUD (ulcer-like, dysmotility-like, reflux-like, and nonspecific) and H. pylori has been identified however the subgroups have been defined, and no specific symptom pattern characterizes patients with H. pylori infection. Whether H. pylori-induced alterations of gastric physiology can explain NUD remains open to debate while we await the results of more specific experiments. Although acid secretion in response to gastrin-releasing peptide may be increased in a subset of NUD patients who are infected with H. pylori, uninfected patients with NUD have not been assessed and the results require confirmation. Most studies suggest no association between H. pylori and gastroduodenal motor or sensory dysfunction in NUD. Treatment trials have been unconvincing. The trials with bismuth therapy have not been adequately blinded. Furthermore, some studies suggest that H. pylori-negative patients with NUD may respond to bismuth treatment, although the results have not been uniform. Therapies aimed at curing H. pylori infection have produced mixed results, with small positive and negative trials. The trials that have used adequate outcome measures have more often than not been negative. Based on current evidence, H. pylori is not established to be of causal importance in NUD.