Campylobacter jejuni is a major cause of human inflammatory enteritis. During the course of human disease numerous proinflammatory cytokines are produced. Little is known, however, about the cytokine responses produced during the interaction of this bacterium with the avian host. Campylobacter has been considered a commensal of the avian host. Any differences in innate responses to this pathogen between the human and avian hosts should lead to a greater understanding of the disease process in humans. We have demonstrated expression of proinflammatory cytokines and chemokines in response to Campylobacter infection in avian primary chick kidney cells and the avian macrophage cell line HD11. The data indicate that Campylobacter can stimulate the avian host in a proinflammatory manner. The data strongly suggest that the lack of pathology in vivo is not due to an inability of Campylobacter to stimulate a proinflammatory response from avian cells.