In split-liver transplantation, the entire portal flow is redirected through relatively small-for-size grafts. It has been postulated that excessive portal blood flow leads to graft injury. In order to elucidate the mechanisms of this injury, we studied the hemodynamic interactions between portal vein- and hepatic artery flow in an experimental model in pigs. Six whole pig liver grafts were implanted in Group 1 ( n=6) and six whole liver grafts were split into right and left grafts and transplanted to Groups 2 ( n=6) and 3 ( n=6), respectively. The graft-to-recipient liver volume ratio was 1:1, 2:3 and 1:3 in Groups 1, 2 and 3, respectively. Portal vein- and hepatic artery flows were measured with an ultrasonic flow meter at 60,120 and 180 min after graft reperfusion. Portal vein pressure was also recorded at the same time intervals. Graft function was assessed at 3,6h and 12h, and morphological changes at 12h after reperfusion. Following reperfusion, portal vein flow showed an inverse relationship to graft size, while hepatic artery flow was reduced proportionately to graft size. The difference was significant among the three groups ( P<0.05). Portal vein pressure was significantly higher in group 3, compared to groups 1 and 2 ( P<0.05). Hepatic artery buffer response was significantly higher in Group 3, compared to Groups 1 and 2 in relation to pre-occlusion values ( P<0.05). Split-liver transplantation, when resulting in small-for-size grafts, is associated with portal hypertension, diminished arterial flow, and graft dysfunction. Arterial flow impairment appears to be related to increased portal vein flow.