BACKGROUND & AIMS: Gastric histology is not well studied in patients with Crohn's disease. The aim of this study was to analyze the histological appearance of gastric mucosa in patients with Crohn's disease.METHODS: In a prospective study, biopsy specimens taken from the antrum and body of 75 patients with known Crohn's disease of the large and/or small bowel and 200 Crohn's disease-free controls were evaluated by histology and immunohistochemistry.RESULTS: Helicobacter pylori-associated gastritis was found in 25 patients with Crohn's disease (33.3%) and 78 controls (39%). In H. pylori-negative patients with Crohn's disease, a characteristic type of gastritis was found in antral biopsy specimens of 36 patients (48%) and in body biopsy specimens of 18 patients (24%). It was characterized by a focal infiltration of CD3+ lymphocytes, CD68R+ histiocytes, and, in 80% of cases, of granulocytes. Granulomas were found in 11 patients. Overall, granulomas and/or focally enhanced gastritis were observed in 76% of H. pylori-negative patients with Crohn's disease and in 0.8% of controls. There were no correlations between the occurrence of focally enhanced gastritis and clinical and laboratory findings.CONCLUSIONS: Focally enhanced gastritis is common in Crohn's disease. Its recognition should guide the clinician into further investigations in patients not yet known to have Crohn's disease.(Gastroenterology 1997 Mar;112(3):698-706)