H. pylori is the cause of one of the most common infectious diseases worldwide. Infection with H. pylori leads to exaggerated synthesis of several inflammatory cytokines. Only a minority of infected patients develops peptic ulcer disease. H. pylori strains associated with peptic ulcer disease induce strong mucosal infiltration with inflammatory cells and increased expression of several cytokines. Cytokines may contribute to ulcer development by different mechanisms, including stimulation of gastrin and pepsinogen release, suppression of somatostatin synthesis and activation of inflammatory cells.