To determine the effect of Helicobacter pylori CagA expression on interleukin‐8 (IL‐8) induction in AGS cells, cagA and five of its fragments from strains 147A and 147C that vary in the 3′ repeat region were cloned into the eukaryotic expression plasmid pSP65SRα. IL‐8, but not RANTES or IL‐Iβ, levels were increased in AGS cells transfected with 147A‐cagA and to a greater extent with 147C‐cagA, compared with negative controls. The 5′ b fragment from the two strains had similar effects, but the 3′ d and e fragments from 147C CagA had greater effects than those from 147A‐CagA. When the Western CagA‐specific sequence (WSS) of 147C‐cagA was replaced with East Asian CagA‐specific sequence (ESS) and cloned into pSP65SRα as an East/West chimera, there was no significant effect on IL‐8 production. Use of specific inhibitors indicates that Src kinase activation, and the mitogen‐activated protein (MAP) kinase and NF‐κB pathways are the major intermediates for CagA effects on IL‐8 induction, but the p38 MAP kinase pathway has little effect. These results indicate a direct CagA effect on IL‐8 induction by gastric epithelial cells, and indicate signal pathway loci that can be targeted for amelioration.