The cardiomyopathy produced by the widely used anticancer drug adriamycin (ADR) is believed to be related to the production of reaction oxygen species and consumption of reduced glutathione (GSH) during redox cycling of the drug. Protection by vitamin E against the toxicity of ADR was studied in a model of compromised isolated hepatocytes, generated by physiological alterations in the concentration of cell calcium. A decrease in cell calcium concentration leads to a greater loss of endogenous α-tocopherol and enhances the intracellular hydrolysis of exogenous α-tocopheryl esters. With this model, vitamin E (α-tocopheryl succinate) at 25 μ m protected the calcium-depleted hepatocytes against the toxicity of ADR, in association with greater cellular α-tocopherol content as compared to calcium-adequate cells. The incubation of calcium-adequate hepatocytes with increasing concentrations of α-tocopheryl succinate up to 200 μ m demonstrated that maximal protection by vitamin E was directly dependent on the α-tocopherol content of the cells, regardless of the concentration of cell calcium. The viability of the cells was closely associated with the α-tocopherol-mediated maintenance of cellular protein thiols. Viability and protein thiol content of the cells were maximal at cellular α-tocopherol levels in the range 0.6–1.0 nmol/10 6 cells in both calcium-depleted and -adequate cells. It is suggested that the potential use of vitamin E as a protective agent against ADR toxicity in vivo be reevaluated with an emphasis placed on the threshold level of intracellular α-tocopherol in the critical target tissue.