Conventional coronary risk factors explain only part of the variation in the incidence of cases of coronary heart disease. Recently H. pylori genomic material has been demonstrated in the coronary arteries of myocardial infarct. In searching for additional coronary risk factors, the potential role of H. pylori infection deserves to be investigated. To clarify if H. pylori infection is associated with an increased risk of coronary heart disease, a series of patients admitted to the Cardiac Catheterization Laboratory for coronary angiography were recruited prospectively. Cases (N = 165) were defined as those who had at least one coronary artery lesion occupying at least 50% of the luminal diameter on coronary angiography. Patients who had normal coronary angiography were selected as controls (N = 127), Demographic data, cardiovascular risk factors, and socioeconomic status were measured in both of the patients and controls. Stored serum specimens from both groups were tested for the presence of serum IgG antibody to H. pylori using enzyme-linked immunosorbent assay; 69.1% of the cases and 77.2% of the controls were seropositive for H. pylori (odds ratio 0.66, 95% CI 0.38-1.16, P = 0.12). After adjustment for age, gender, cardiovascular risk factors, and socioeconomic class, this remained nonsignificant (odds ratio 0.59, 95% CI 0.32-1.09, P = 0.09). H. pylori seropositivity was not associated with several coronary risk factors in either cases or controls. The proportion of H. pylori-positive patients was higher among the cases with triple vessel disease (77.5%) than those with double vessel disease (67.3%) and single vessel disease (65.7%); however, the differences were not statistically significant (odds ratio 0.57, 95% CI 0.23-1.4, P = 0.19). In this study no increase was found in H. pylori seropositivity in subjects with coronary artery disease. This minor association suggests that previous H. pylori infection, reflecting the early childhood environment, may not be important in determining the risk of coronary heart disease.