Primary graft dysfunction occurs in up to 10% of liver transplant recipients and is the major reason for early mortality and retransplantation. The conventionally used markers of early graft function--i.e., correction of acidosis, glucose requirement, consumption of potassium, serum alanine transaminase (ALT), prothrombin time (PT), bile flow, resolution of encephalopathy and haemodynamic instability can be very misleading as they are dependent on numerous other factors. The aim of this study was to assess the use of indocyanine green clearance (ICG) as a measure of graft function. Peripheral ICG clearance was measured 18-24 hr after liver transplantation in twenty-three consecutive patients (24 transplants). Doppler ultrasonography confirmed normal hepatic arterial blood flow. Correlations between ICG clearance and other markers of graft function and outcome were sought. The mean ICG clearance was 406 mls/min (SD 137.5). A threshold value of 200 ml/min reliably predicted outcome. Significant correlations were found between ICG clearance and times to normalization of PT (P < 0.02) and to the correction of acidosis (P < 0.05). No correlation was found with ALT, PT, bile flow, glucose requirement, or consumption of potassium. ICG clearance measured on the day after liver transplantation accurately reflects graft function and may be used to predict graft survival and final outcome.