We investigated the variation in the protection of energy status by isoflurane in isolated hepatocytes with the isoflurane dose, duration of anoxia, and reoxygenation by measurements of ATP, ADP, and AMP, in the cells. During 30 min of anoxia, in the presence of 1.4, 2.8, 4.2% isoflurane the ATP concentration was more than that with 0% isoflurane. With a 30-35 min incubation in the presence of 1.4% isoflurane, there was a modest decrease in energy charge during anoxia, partially prevented by isoflurane and completely reversed by reoxygenation, and no decrease in the total adenine nucleotide. With a 90-120 min incubation, isoflurane partly prevented the decreases in both energy charge and total adenine nucleotide during both anoxia and reoxygenation. We conclude that at doses in the clinical range, isoflurane partially protected isolated hepatocytes against decreases in both energy charge and total adenine nucleotide occurring either during short or long anoxia.