BACKGROUND The prevalence of intestinal metaplasia (IM) in underlying Helicobacter pylori gastritis was studied in 1446 patients. METHODS Antral and body mucosa biopsy specimens (stains: hematoxylin and eosin, Warthin-Starry) were taken from five groups of patients: gastritis with no lesions, gastritis with duodenal, pyloric, or gastric ulcers or with chronic antral erosions. RESULTS The prevalence of IM was higher in the antral than in the body mucosa (22.9% versus 2.8%; p < 0.001). Patients with IM had a higher mean age than those without IM in the overall group (p < 0.01). IM could be detected with the highest frequency in patients with gastric ulcers (p < 0.001). CONCLUSIONS The higher prevalence of IM in the antral mucosa--the preferred location of gastric carcinomas--further supports the postulated association of H. pylori and gastric carcinoma. The various prevalences of IM might contribute to explaining the different probabilities of gastric carcinoma developing in the groups investigated.