Arterial ketone body ratio (AKBR) was measured serially in 49 pediatric orthotopic liver transplantations. The AKBR pattern correlated with hepatic synthetic function, as well as with short-term graft and patient survival. A rapid recovery pattern of AKBR to above 1.0 within 40 hr after reperfusion was associated with 94% graft and patient survival. Pediatric liver grafts were found to have better tolerance to low energy levels when compared with previously published data for adult OLT. The salvage rate of pediatric grafts exhibiting a slow recovery pattern (AKBR 0.7-1.0) was 71%. No recovery pattern (AKBR < 0.7) was seen in all 6 cases of primary nonfunction, and in 3 of 4 cases of early hepatic artery thrombosis (HAT). All these grafts were lost; however, 56% of the children in this group survived retransplantation. Unlike the PNF grafts, the no recovery pattern after HAT was characterized by gradual improvement of the synthetic function, despite the low energy state.