Some clinical isolates of nonopsonized H. pylori have the ability to activate neutrophils to an oxidative burst (neutrophil activating capacity, NAC), and such strains were significantly more often isolated from patients with peptic ulcer disease and active chronic gastritis. The purpose of the present work was to investigate the effect of rebamipide (Mucosta) on the release of reactive oxygen metabolites from neutrophils activated by various strains of H. pylori with or without NAC, nonopsonized or opsonized, using as controls fMLP and PMA, known activators of neutrophils, and to study the kinetics of these events by luminol-enhanced chemiluminescence and by flow cytometry. The results showed that the oxidative burst induced in neutrophils by fMLP and by nonopsonized or opsonized H. pylori with NAC was inhibited by rebamipide in a dose-dependent manner both in the early and late phases of activation. In contrast, the oxidative burst induced by opsonized H. pylori without NAC was not inhibited by rebamipide, which might indicate that it does not have the ability to block CR1 or CR3 receptors involved in opsonic phagocytosis but still has the ability to block the receptor(s) for NAC. The oxidative burst induced by PMA, which primarily activates protein kinase C, was not inhibited in the early phase but diminished 40-45% in the late phase with the 2 mM concentration of rebamipide, probably due to scavenging of reactive oxygen species. In conclusion, rebamipide has the ability to diminish the oxidative burst of neutrophils activated by nonopsonized or opsonized H. pylori organisms with neutrophil activating capacity, most likely through the blocking of fMLP-related receptors, inhibition of the production of reactive oxygen species, and the scavenging of such metabolites. Rebamipide may therefore be useful to prevent gastroduodenal lesions associated with gastric mucosal inflammation in H. pylori infection.