Recent studies have shown that platelet-activating factor (PAF) is involved in ischemia/reperfusion injury to the liver. We therefore examined changes in PAF in recipients during liver transplantation. The level of PAF increased after portal venous reperfusion, except in one case where veno-venous bypass was applied. A marked elevation was noted in another case where portal congestion occurred due to outflow block, followed by prolonged graft dysfunction. These results suggest that elevation of the PAF level is related to portal congestion, and that PAF might be involved in postoperative liver graft dysfunction.