In contrast to traditional static cold preservation of donor livers, normothermic machine perfusion may reduce preservation injury, improve graft viability and potentially allows ex vivo assessment of graft viability before transplantation. We have studied the feasibility of normothermic machine perfusion in four discarded human donor livers. Normothermic machine perfusion consisted of pressure and temperature controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion for 6 h. Two hollow fiber membrane oxygenators provided oxygenation of the perfusion fluid. Biochemical markers in the perfusion fluid reflected minimal hepatic injury and improving function. Lactate levels decreased to normal values, reflecting active metabolism by the liver (mean lactate 10.0 ± 2.3 mmol/L at 30 min to 2.3 ± 1.2 mmol/L at 6 h). Bile production was observed throughout the 6 h perfusion period (mean rate 8.16 ± 0.65 g/h after the first hour). Histological examination before and after 6 h of perfusion showed well-preserved liver morphology without signs of additional hepatocellular ischemia, biliary injury or sinusoidal damage. In conclusion, this study shows that normothermic machine perfusion of human donor livers is technically feasible. It allows assessment of graft viability before transplantation, which opens new avenues for organ selection, therapeutic interventions and preconditioning.