A long-lasting condition of hypochloridria leads to a bacterial growth both in the gastric lumen and biopsies of human stomach. Some of these bacteria are probably involved in gastric carcinogenesis, due to their capacity of nitrosation. This study was carried out on biopsies taken during endoscopy from both gastric antrum and the body of patients with or without hypochloridria. Scanning electron microscopy observation shows that bacteria, other than Helicobacter pylori, found in hypochloridria, can be located not only over but also into and under the mucus layer covering the gastric epithelium. In such areas, mechanical and biochemical damage may occur.