BACKGROUND: The adhesion of H. pylori to the gastric epithelial cells may be an essential step for the pathophysiology of various H. pylori-induced gastrointestinal diseases. The purpose of this study was to investigate the ultrastructural relation of H. pylori and gastric epithelial cells in their adhesion. METHODS: Endoscopic biopsy of gastric antrum and body was performed from 15 patients (9 men, 6 women) with chronic gastritis and H. pylori infection. The specimens were processed for electron microscopy and observed with a transmission electron microscope (Hitachi H-600). RESULTS: On the basis of morphological appearances, the adhesions of H. pylori to the gastric epithelial cells were categorized into three types; filamentous connection, adhesion pedestals and membrane fusion. Coccoid and undetermined forms adhered mainly by the filamentous connection, whereas the bacillary forms adhered primarily by the adhesion pedestals and membrane fusion. CONCLUSION: Various types of adhesion were associated with H. pylori and gastric epithelium. Further studies are needed to evaluate the influence of different types of adhesion to the pathophysiology of H. pylori.