Previously, two different mechanisms were suggested to be involved in the hepatocellular injury caused by TBHP: peroxidation of the cell membrane lipids, and a disturbance of cytosolic calcium homeostasis. In this study, the cytosolic calcium-ion chelator BAPTA-AM suppressed the hepatocellular injury by TBHP at extracellular calcium-ion concentrations of 0, 1, and 3 mM, independent of peroxidation of the cell membrane lipids and the mitochondrial membrane potential. Therefore, a disturbance of cytosolic calcium homeostasis plays the major role in the hepatocellular injury caused by TBHP.