After ischemia-reperfusion, polymorphonuclear leukocytes (PMNLs) become activated by inflammatory mediators, adhere to the vascular endothelium via the interaction of specific adhesion molecules, and cause tissue injury by the release of cytotoxic oxygen radicals and enzymes. Results obtained in animal experiments suggest a key role for PMNLs in ischemia-reperfusion injury of transplanted livers; therefore, we studied the expression of adhesion molecules on circulating PMNLs (β2 -integrins [CD18] and l -selectin [CD62L]) in 20 patients undergoing orthotopic liver transplantation (study group). To determine the effects of surgical trauma to the liver in the absence of ischemia and reperfusion, the expression of PMNL adhesion molecules was measured in 10 patients scheduled for elective partial liver resection without hepatic vascular exclusion (control group). Patients were classified as responders or nonresponders based on changes in the expression of adhesion molecules elicited by reperfusion. In the control group, all patients remained nonresponders, showing that surgical trauma of the liver alone does not cause activation of circulating PMNLs. In contrast, 8 of 20 patients in the study group were classified as responders. In responders, postoperative serum liver enzyme activities were significantly higher than in nonresponders, indicating that activation of PMNL was associated with damage to hepatocellular integrity. Because expression of adhesion molecules was already changed during surgery, monitoring of the expression of β2 -integrins and l -selectin on circulating PMNLs during orthotopic liver transplantation might be useful in prediction of early graft dysfunction.