The frequency of gastric Crohn's disease has been considered low. This study was undertaken to determine the prevalence of chronic gastritis and Helicobacter pylori infection in patients with Crohn's disease. Oesophagogastroduodenoscopy was performed on 62 consecutive patients suffering from ileocolonic Crohn's disease. Biopsy specimens from the antrum and corpus were processed for both histological and bacteriological examinations. H pylori antibodies of IgG and IgA classes were measured in serum samples by enzyme immunoassay. Six patients (9.7%) were infected with H pylori, as shown by histology, and in five of them the infection was also verified by serology. Twenty one patients (32%) had chronic H pylori negative gastritis (negative by both histology and serology) and one of them also had atrophy in the antrum and corpus. Granulomas were found in four patients. The characteristic appearance of H pylori negative gastritis was focal and mostly mild inflammation resembling the inflammatory changes seen in the gut in Crohn's disease. Patients with H pylori negative chronic gastritis had a significantly more active disease in their gut than those with normal gastric mucosa (p < 0.01). It is concluded that H pylori positive gastritis is rare, while H pylori negative gastritis is relatively common in patients with Crohn's disease. H pylori negative 'Crohn's gastritis' seems to be associated with active Crohn's disease.