The results of PCR-based molecular typing of Helicobacter pylori strains by restriction fragment length polymorphism analysis of a 1, 161-bp nucleotide sequence of the midregion of the vacA gene are reported. A total of 48 H. pylori strains isolated from gastric biopsy specimens obtained from 18 patients with peptic ulcer dyspepsia, 15 patients with nonulcer dyspepsia, and 15 asymptomatic H. pylori-infected subjects were studied. Highly heterogeneous restriction patterns were obtained by digestion of PCR products with SauII, BglII, and HhaI, whereas HaeIII digestion resulted in a strictly homogeneous profile for H. pylori strains isolated from 14 of 18 (77.7%) patients with peptic ulcer dyspepsia, but a strictly homogeneous profile was found for strains from only 8 of 15 (53.3%) patients with nonulcer dyspepsia (P = 0.163) and 5 of 15 (33.3%) asymptomatic H. pylori-infected subjects (P = 0.014). A potentially important aspect of the results obtained is the clinical relevance, since a single restriction pattern seems to be able to identify the majority of H. pylori strains associated with peptic ulcer disease.