Seventy one patients who had had operations on their stomachs over 15 years previously were examined by endoscopy and multiple mucosal biopsy sampling. Sixty six had histologically proved gastritis (56 chronic atrophic gastritis, 10 superficial gastritis), 38 intestinal metaplasia, and 11 epithelial dysplasia. In three cases the epithelial dysplasia was severe (carcinoma in situ). One patient had an infiltrating carcinoma and another, whose biopsy appearances were reported as severe dysplasia, developed a carcinoma of the stomach eight months later. All patients having undergone gastric surgery more than five years previously should be screened endoscopically and any found to have moderate dysplasia subjected to regular endoscopic screening thereafter. Patients with severe dysplasia (carcinoma in situ) should be considered for radical surgery.