Our objective was to determine whether the prevalence of vacuolating cytotoxin production differed among Helicobacter pylori isolates obtained from patients with chronic gastritis, gastric ulcer, or duodenal ulcer. We examined the vacuolating cytotoxin production of 114 clinical H. pylori isolates in rabbit gastic epithelial cells (RGECs). We also tested two positive control strains (NCTC 11637 and NCTC 11916). Seventy-four of the 114 H. pylori clinical isolates (64.9%) produced intracellular vacuolation in RGEC cells: but there was no significant difference in the prevalence of intracellular vacuolation among the isolates of patients with chronic gastritis, gastric ulcers, and duodenal ulcers. We found no strong correlation between vacuolating cytotoxin production and peptic ulceration.