Determination of cellular enzyme activities in washout preservation solution used in hypothermic liver graft storage may allow development of an index that could be clinically valuable in prediction of early post-transplant graft function. In the present study, we collected washed out preservation fluid at the time of graft rinsing from 53 liver recipients. Aspartate aminotransferase and, to a lesser extent, lactate dehydrogenase levels correlated with early postoperative graft viability as assessed by 1-month graft survival and standard biochemical indices of liver function. Those patients with the highest aspartate aminotransferase activity in the washout preservation solution experienced the highest levels of this enzyme postoperatively (area-under-the-curve day 1-3; 1340 vs. 788 IU/L), total bilirubin (area-under-the-curve day 1-5; 901 vs. 538 mumol/L), and rejection frequency (67% vs. 31%) (all P < 0.05), with a significantly lower 1-month graft survival rate compared with patients with low effluent levels (62% vs. 92%, P < 0.05). Two markers of endothelial cell damage, purine nucleoside phosphorylase and a creatine kinase isoenzyme, measured in the fluid did not correlate with early graft viability. It is suggested that assay of aspartate aminotransferase activities in preservation fluid washout samples is a clinically useful indicator of graft viability.