Chemokines are a family of low-molecular-weight proinflammatory cytokines that have leukocyte chemotactic and activating properties. Chemokine protein and mRNA are increased in the gastric mucosa of Helicobacter pylori infection and they are considered to regulate migration of leukocyte populations. The increase of C-X-C chemokines (e.g. IL-8, GRO-alpha) which effect primarily neutrophils is significantly associated with gastric polymorphonuclear cell activity suggesting that these chemokines play a primary role in active gastritis induced by H. pylori infection. In vitro enhanced epithelial chemokine responses are induced by cagA positive strains which have been clinically associated with more severe clinical outcome. Infection with cagA-positive H. pylori strains associates in vivo specifically with a C-X-C profile and enhanced polymorphonuclear infiltration in the gastric mucosa. Whilst infection with H. pylori, especially cag positive strains, is associated with more severe disease, genetic variability in host chemokine responses may also contribute to disease outcome.