Since the exact mechanisms of the pathogenicity of Campylobacter pylori are not known, we performed an ultrastructural study with the aim of focusing on patterns of possible physical contact between C. pylori and gastric epithelium, and of considering them in relation to the bacterial pathogenicity. Among 20 random consecutive patients referred for routine gastroscopy, we studied ultrathin sections from the 11 patients with Campylobacter-like organisms, and recognized three patterns of physical contact between bacteria and epithelial cells. These patterns seem in accord with published data of C. pylori toxicity, and they could represent different evolutive stages of the infection.