Vanadium (V) as sodium orthovanadate induces an increase in lipid peroxidation in the kidneys after a single subcutaneous or intraperitoneal injection to rats or mice. The rate of malondialdehyde (MDA) formation, an index of lipid peroxidation, by kidney homogenates increased by more than 100% 1 h after injection. Chronic exposure of rats to vanadium sulfate, initially through maternal milk and later in the drinking water, resulted after 10 weeks in a significant increase in MDA formation by kidney but not by other tissues. In both acute and chronic studies in rats and mice, no significant increase in lipid peroxidation by V treatment was detected in brain, heart, lung, spleen, or liver. In mice, administration of ascorbate prior to acute exposure to V diminished both toxicity, i.e., respiratory depression and limb paralysis, and the formation of MDA in kidney.