In an attempt to determine the initial function of hepatic allografts, several metabolic indicators of hepatic function were studied intraoperatively in 12 cases of hepatic transplantation. The operation was divided into three sampling periods: baseline, anhepatic, and reperfusion. During the baseline period plasma lactate levels rose at 2.6 mmol/L/hr and continued to rise at a similar rate during the anhepatic period. Baseline period total free plasma amino acid levels (TFPAA) rose at a moderate rate of 0.4 mmol/L/hr. During the anhepatic period TFPAA levels rose at a fivefold greater rate than during baseline (p less than 0.01). The ability of the hepatic allograft to reduce abnormal levels of TFPAA and lactate during the reperfusion period was associated with reduced morbidity in the first 48 hours after transplantation. Intraoperative clearance of accumulated TFPAA is currently the best means of assessing initial allograft function. Elevated preoperative total serum bilirubin levels were also associated with increased early morbidity in hepatic transplant recipients.