Exposure of isolated hepatocytes to a polychlorinated biphenyl mixture induced a rapid loss of cell viability. The effect was not dose-dependent. The biochemical effects in the cellular toxicity did not involve glutathione content, protein sulfhydryl groups and lipid peroxidation. A transient increase in cytosolic Ca2+ was observed after exposing the hepatocytes to the polychlorinated biphenyl mixture. Our findings indicate that polychlorinated biphenyls are able to kill hepatocytes and suggest that elevation of cytosolic Ca2+ concentration could be responsable of the toxicity.