The anticoagulant effect of nafamostat mesilate(FUT, a protease inhibitor) plus cepharanthin (CE) after small-caliber graft implantation into the canine jugular veins was compared with that of heparin (HE) or urokinase (UK). Twenty-four dogs were used in this study. Sauvage EXS Dacron grafts 5mm in diameter were implanted into external jugular veins. Immediately after impantation, continuous administration of drugs was started through posterior auricular veines. Coagulation test were carried out serially during perfusion. Three hours after implantation, the grafts were removed and examined macro-and microscopically. The dogs were divided into 4 groups : 1)Control group ; 2)UK group (2000u/kg/hr) ; 3)HE group (0.25mg/kg/hr) ; and 4)FUT plus CE group, FUT (0.3mg/kg/hr) plus CE (0.7mg/kg/hr). All grafts were thrombosed in the control group and UK group. However, no thrombus was found in the HE group anf FUT plus CE group. Coagulation tests revealed that fibrinogen and AT-Ⅲ decreased significantly in the UK group (p<0.05), ACT and APTT was gradually prolonged in the HE group (p<0.05), and there was no significant change in the FUT plus CE group. These findings suggest that FUT plus CE may not only decrease early thrombus formation, but may also maintain the balance of the coagulation system. The combination of FUT plus CE may be useful anticoagulant therapy during the postoperative period when the risk of bleeding remains.