C-X-C chemokines are potent chemoattractants that are believed to mediate neutrophilic inflammation in several organs. Recent studies suggest a role for C-X-C chemokines in the pathogenesis of neutrophilic hepatitis but do not prove causation. We investigated the biological consequences of hepatic chemokine production in vivo by transiently overexpressing cytokine-induced neutrophil chemoattractant (CINC), a member of the C-X-C chemokine family, in intact rats. Rats were injected intraportally with a replication-defective recombinant adenovirus containing the CINC complementary DNA (cDNA). Within 4 days, treated animals had high levels of CINC in both liver tissue and plasma Rats overexpressing CINC exhibited an eightfold increase in circulating neutrophils; they also developed severe hepatic injury, characterized by a 6- to 25-fold increase in plasma transaminases and marked hepatic inflammation on biopsy. Liver disease in CINC-producing rats correlated positively with the number of neutrophils sequestered in the hepatic parenchyma. Tissue injury was attributed directly to chemokine overproduction, because control rats infected with adenoviruses lacking the CINC cDNA did not produce CINC and developed only minor hepatic abnormalities. These experiments provide direct evidence that C-X-C chemokines, when expressed in sufficient quantity in the liver in vivo, induce neutrophil recruitment and tissue invasion and provoke severe liver injury. The data suggest that C-X-C chemokines have important pathogenic potential in both clinical and experimental liver disease.