The effects of volatile anesthetics were assessed in freshly isolated rat hepatocytes by surface-scanning electron microscopy and by measuring leakage of cellular enzymes, lactate dehydrogenase and β-glucuronidase into the surrounding medium. The order of potency in regard to their capacity to produce alterations of these parameters was halothane = methoxyflurane > ether = control. The extent of enzyme leakage from hepatocytes exposed to halothane or methoxyflurane was both dose dependent and, for the first 30 minutes, time dependent. Surface scanning of the isolated hepatocytes showed that both halothane and methoxyflurane produced enzyme leakage and morphoiogic changes in cellular membranes, but ether did not. These studies demonstrate that scanning electron microscopy and enzyme leakage from cells are useful for the evaluation of drug-induced changes in lever cells in vitro. The relation between these drug-induced changes and clinical hepatotoxicity remains to be elucidated.