Autoimmunity, a feature of chronic infection by Helicobacter pylori, is first directed against gastric cells but is also associated with extragastric diseases. The aim of the present work was to look for the influence of the infection on induction of non-organ-specific autoantibodies (NOSAs). We compared 49 patients (28 males and 21 females; age range, 36-72 years; mean, 61 +/- 4.6 years) suffering from duodenal ulcer and H. pylori infection (Group A) to 38 subjects (20 male, 18 female; age range, 40-78 years; mean, 63 +/- 3.8 years) affected by duodenal ulcer related to the assumption of nonsteroidal antiinflammatory drugs (Group B). H. pylori infection was diagnosed by histology, 13C-urea breath test, and serum IgG antibodies. Autoimmunitary pattern was demonstrated by the presence of NOSAs in serum. Antinuclear (ANA), anti-smooth muscle (SMA), and anti-liver/kidney microsomal-1 (LKM-1) antibodies were present in 5 of 49 (10.2%), 2 of 49 (4%), and 0 Group A patients, respectively. In Group B, ANA was present in 3 of 38 (7.9%), SMA in 3 of 38 (7.9%), and anti-LKM-1 in 0 patients. The difference was not statistically significant. In this population, H. pylori infection is not associated with an increased prevalence of NOSAs.