To assess the possibility that Campylobacter pylori might colonise heterotopic gastric mucosa a detailed histological review of 69 cases of Meckel's diverticula resected over 17 years was undertaken. Twenty three were resected incidentally while 46 were excised as the suspected cause of symptoms. Gastric mucosa was found in 13 diverticula (19%), 10 from the symptomatic group and three from the incidental cases, of which eight showed active gastritis affecting the heterotopic mucosa. Specific staining showed spiral bacteria with the typical morphology of C pylori adherent to gastric mucosa in four of the diverticula showing active gastritis. Campylobacter-like organisms were not seen on normal heterotopic gastric mucosa or on adjacent intestinal epithelium. The findings show that Campylobacter-like organisms, identical in appearance, staining, and distribution with C pylori, colonise and possibly inflame heterotopic gastric mucosa in Meckel's diverticulum.