The present study aims at investigating the effects of mannitol and dimethylthiourea, known hydroxyl radical scavengers, on lipid peroxidation as an indicative of oxidative damage, NF-kappa B activation and IL-8 production by Helicobacter pylori in gastric epithelial cells. A human gastric epithelial cell line, AGS, treated with or without mannitol and dimethylthiourea, was incubated in the absence or the presence of H. pylori. As a result, H. pylori significantly stimulated the productions of lipid peroxide and IL-8. Treatment with H. pylori resulted in the activation of two species of NF-kappa B dimers (a p50/p65 heterodimer and a p50 homodimer). Mannitol and dimethylthiourea significantly inhibited lipid peroxide production, NF-kappa B complex formation and IL-8 production by H. pylori. In conclusion, mannitol and dimethylthiourea may attenuate H. pylori-induced gastric inflammation by inhibiting lipid peroxidation and NF-kappa B activation and thereby decreasing IL-8 production.