The release of heparin has been mentioned as one of the causes of hypocoagulability after reperfusion of the liver graft. It has been ascribed to endogenous heparin released from the donor liver or to exogenous heparin in the preservation fluid that is released into the recipient after sequestration into the graft during preservation. The aim of this study was to investigate whether systemic administration of heparin to the donor before the hepatectomy contributes to the appearance of heparin in the recipient after reperfusion. We studied 20 patients undergoing an auxiliary heterotopic liver transplantation; 15 donors had received heparin immediately before circulation arrest (median 300 IU/kg body weight), but 5 had not. The thrombin time (TT), activated partial thromboplastin time (aPTT), and heparin neutralization test were determined at several intervals during the transplantation.