To investigate the mechanism of the hypergastrinaemia associated with Helicobacter pylori infection by examining the effect of H. pylori infection and the cytokine tumour necrosis factor-alpha (TNF-alpha) on gastrin release from human antral fragments. In-vitro experimental study. Human antral biopsy fragments were cultured for 6 h with and without TNF-alpha (20 ng/ml) and the gastrin released over the following 2-h stimulation period measured by radioimmunoassay. The integrity of the paracrine feedback loop inhibiting gastrin release was tested by concurrent administration of cholecystokinin (CCK). H. pylori-positive fragments were associated with significantly greater bombesin-stimulated gastrin release (increased by 40%, P < 0.05) and less inhibition produced by CCK administration (decreased by 55%, P < 0.05), than H. pylori-negative fragments. TNF-alpha treatment of H. pylori-negative fragments significantly enhanced bombesin-stimulated gastrin release (by 82%, P < 0.01) and diminished inhibitory feedback by CCK (by 53%, P < 0.05). H. pylori infection is associated with enhanced gastrin release from human antrum and TNF-alpha produces a similar effect. Proinflammatory cytokines generated in the antrum in response to the infection are likely to play a significant role in the hypergastrinaemia of H. pylori infection.