Menadione is a commonly used compound that causes oxidative stress. We investigated the influence of lipid peroxidation on the apoptotic response of mouse myogenic C2C12 cells following menadione-induced oxidative stress. The presence of hypodiploid cells and phosphatidylserine translocation were assayed to detect apoptotic cells. Menadione at 10-40 micro M induced cell apoptosis. Menadione at dose of 80 micro M induced both apoptosis and necrosis. At a 160 micro M dosage, menadione induced cell necrosis. Caspase 3 activation is required for menadione-induced apoptosis. Incubation of cells with 40 micro M menadione resulted in the depletion of cellular glutathione and increased lipid peroxidation. Pre-treatment of cells with cysteine suppressed the menadione-induced apoptosis and prevented changes in reactive oxygen species levels, glutathione levels and lipid peroxidation. Pre-treatment of cells with deferoxamine mesylate, an iron chelator, also reduced both menadione-induced apoptosis and lipid peroxidation. However, this did not prevent menadione-induced glutathione depletion. Thus, the inhibition of lipid peroxidation by deferoxamine mesylate prevented apoptosis even though cellular glutathione remained depleted. Our data suggest that menadione-induced apoptosis is directly linked to iron-dependent lipid peroxidation.