The most important problem in the living donor adult liver transplantation (LDALT) is a small for size graft. Although a right lobe graft is used in many cases in order to avoid small for size graft, for a donor, the risk has few in left lobe graft. We evaluate the effect of an intraportal infusion treatment to the small for size graft. One hundred and twelve patients who underwent LDALT were studied. The graft weight recipient standard liver volume ratio (GV/SLV) of these patients were 50% or less. We divided the patients into following two groups; infusion group (n = 53) and control group (n = 59). For the infusion group, 16 G double lumen catheter was inserted into portal vein and nafamostat mesilate (protease inhibitor which stabilize coagulofibrinolytic state; 200 mg/day), prostaglandin E(1) (vasodilator and hepatoprotective effect; 500 microg/day) and thromboxane A(2) synthetase inhibitor (vasodilator and anticoagulant effect; 160 mg/day) were administrated continuously for 7 days. Small-for-size graft syndrome was defined as bilirubin >10 mg/dl and ascites >1000 cc on postoperative day (POD) 14. Comparison examination of a background factors and postoperative bilirubin and amount of ascites was carried out. The mean GV/SLV did not have the difference at 39.1% of infusion group, and 38.3% of control group (P = 0.58). By the control group, 15 patients (25.4%) were small-for-size graft syndrome, however, there was only two (3.8%) small-for-size graft syndrome in infusion group (P = 0.04). The bilirubin levels of infusion and control group on 7 and 14 POD were 9.9 and 7.8 vs. 9.5 and 10.5 mg/dl, respectively. The amount of ascites of infusion group on 7 and 14 POD were 870 and 430 cc, respectively. On the contrary, in control group, the amount of ascites on 7 and 14 POD were 1290 and 1070 cc, respectively. Bilirubin levels and the amount of ascites on 7 and 14 POD were lower in the patients with infusion group then those with control group. There were no differences between infusion group and control group in age, sex and Child's classification. The intraportal infusion had an effect in prevention of hyperbilirubinemia and loss in quality of excessive ascites in the patients with small for size graft. This was suggested to be what is depended on the improvement of the microcirculation insufficiency considered one of the causes of small-for-size graft syndrome.