Background. homB codes for a putative Helicobacter pylori outer membrane protein and has previously been associated with peptic ulcer disease (PUD) in children. Methods. A total of 190 H. pylori strains isolated from children and adults were studied to evaluate the clinical importance of the homB gene. In vitro experiments were performed to identify HomB mechanisms of bacterial pathogenicity. Results. Characterization of the isolates demonstrated that homB was significantly associated with PUD in 86 children (odds ratio OR, 7.64 95% confidence interval {CI{, 2.65–22.05) and in 32 adults ⩽40 years of age (OR, 11.25 95% CI, 1.86–68.13). homB was correlated with the presence of cagA, babA2, vacAs1, hopQI, and oipA “on” genotype (P < .001). The HomB protein was found to be expressed in the H. pylori outer membrane and was noted to be antigenic in humans. H. pylori homB knockout mutant strains presented reduced ability to induce interleukin-8 secretion from human gastric epithelial cells, as well as reduced capacity to bind to these cells. Both of these functions correlated with the number of homB copies present in a strain. Conclusion. homB can be considered a comarker of H. pylori strains associated with PUD. Moreover, results strongly suggest that HomB is involved in the inflammatory response and in H. pylori adherence, constituting a novel putative virulence factor.