Lipopolysaccharides of Helicobacter pylori express Lewis X similar to that occurring in gastric mucosa. Patients infected with H. pylori produce anti-Lewis X antibodies. The aim of this study was to examine whether anti-Lewis X antibody was associated with the development of gastric cancer, particularly intestinal type cancer. Serum sample was collected from 98 patients with early gastric cancer and 98 gender- and age-matched control subjects who underwent endoscopy. Histologically, 77 cancers were of the intestinal type. Titers of anti-H. pylori and anti-Lewis X immunoglobulin G (IgG) antibodies were assayed by enzyme-linked immunosorbent assay. The mean titer of Lewis X antibody was 0.097 in patients with gastric cancer and 0.110 in matched control subjects (not significant). In 72 H. pylori-seropositive patients with intestinal type cancer and their matched H. pylori-seropositive controls, mean titer was 0.115 and 0.107, respectively (not significant). The odds ratio for the risk of gastric cancer if Lewis X antibody was high titer was 0.93 (95% CI 0.43-2.00). The odds ratio for the risk of intestinal type gastric cancer in patients with H. pylori infection if Lewis X antibody was high titer was 1.10 (95(% CI, 0.46-2.62). Anti-Lewis X antibody does not seem to be associated with the development of gastric cancer, even the intestinal type cancer.