Helicobacter pylori (H. pylori) is causally related to chronic active gastritis, peptic ulcer disease, primary low-grade B-cell gastric lymphoma, and is also a risk factor for gastric cancer. In addition, a high seroprevalence of H. pylori has been found in many extragastrointestinal disorders, including active bronchiectasis and chronic obstructive pulmonary disease (COPD). It appears that H. pylori has a close relationship with respiratory diseases, but data in the literature on the relationship between H. pylori infection and asthma are poor. We therefore investigated the relationship between them. In this study we evaluated 46 patients with mild asthma, 48 age- and sex-matched patients with peptic ulcer and 48 healthy control subjects. All enrolled subjects underwent a serologic test for H. pylori IgG and cytotoxin-associated gene-A (CagA) by enzyme-linked immunosorbent assay (ELISA). There was no significant difference in both anti-H. pylori IgG seropositivity (p=0.6580) and anti-H. pylori-CagA IgG seropositivity (p=0.7183) between the asthmatic and control subjects. In contrast, both anti-H. pylori IgG seropositivity and anti-H. pylori-CagA IgG seropositivity were significantly higher in peptic ulcer patients than these in asthmatic patients (p<0.01). Despite the sero-epidemiological association of H. pylori infection with many inflammatory conditions, our data show no significant association between mild asthma and H. pylori infection.