BACKGROUND: In recent studies, familial coinfection with the same Helicobacter pylori strains has been indicated, but more data are necessary to confirm intra-familial spread of the micro-organism. AIMS: The aim of this study was (a) to assess the frequency of H pylori infection in spouses of patients with duodenal ulcers and (b) to investigate the possibility of intraspousal typing of the respective strains. PATIENTS: Sixty four patients with duodenal ulcer and their spouses were included in the study. METHODS: The H pylori infection was confirmed after endoscopy by culture and histological examination of biopsy specimens, and CLO test. The isolates were compared on the basis of their rRNA gene patterns (ribopatterns) after digestion of chromosomal DNA by the restriction endonucleases HaeIII or HindIII. RESULTS: Of the patients, 54 were found to be H pylori positive. Of the respective spouses, 42 (78%) were also H pylori positive. In contrast, only two out of 10 (20%) partners of H pylori negative patients were infected. Ribopatterns of H pylori strains derived from 18 patients and their spouses showed that in each of eight couples a single strain had colonised both partners, while in the remaining 10 couples each partner was colonised by a distinct H pylori strain. CONCLUSIONS: These data suggest person to person transmission within couples or exposure to a common source of infection.