Animal studies suggest that acute phase reactant cytokines and polymorphonuclear leukocytes (PMN) may play a critical role in ischemia- reperfusion injury. To evaluate whether similar mechanisms are operative in human liver, six cirrhotic and nine noncirrhotic patients undergoing right hepatectomy were randomized for utilization of hepatic vascular exclusion (HVE) as a model of ischemia-reperfusion injury. Portal and systemic levels of acute reactant cytokines (interleukin 6 [IL-6], interleukin 1 [IL-1], tumor necrosis factor α [TNF-α]) and neutrophil adhesion in serial liver biopsy specimens were studied. Correlations among mediators, leukocyte adhesion, and markers of liver injury were also evaluated. Hepatic vascular exclusion resulted in substantial and reproducible changes in portal and arterial IL-6 levels in both cirrhotic and noncirrhotic patients. Portal and systemic cytokine levels were comparable in most instances, whereas levels were usually higher in cirrhotic patients than in noncirrhotic patients. Negative correlations were found between IL-6 levels at the time of reperfusion and later TNF-α levels. IL-6 levels correlated negatively with numerous markers of hepatocellular injury and the number of postoperative complications. Hepatic vascular exclusion increased neutrophils adhesion after reperfusion in cirrhotic patients but not in noncirrhotic patients. In cirrhotic patients, the degree of leukocyte adhesion after reperfusion correlated with several postoperative markers of liver injury. This study in humans shows that acute reactant cytokines are released during liver ischemia and, interestingly, that IL-6 levels strongly correlate with clinical and laboratory measures of injury. Further studies to evaluate possible causal relationship with hepatic injury are warranted, with emphasis on the role of IL-6 and PMN adhesion.