AbstractThere is currently considerable interest in what is termed “oxidative stress,” or the oxidation of biological macromolecules, with emphasis on its involvement in various diseases and toxicities and methods to limit either its occurrence or effects. This unit describes traditional methods to measure the extent or rate of lipid peroxidations, including assays for conjugated dienes, lipid hydroperoxides, the polyunsaturated lipid breakdown product malondialdehyde, and hemolysis, along with discussion of alternative methods.