Quantification of lipid peroxidation is essential to assess the role of oxidative injury in pathophysiological disorders. Lipid peroxidation results in the formation of highly reactive and unstable hydroperoxides of both saturated and unsaturated lipids. Our Lipid Hydroperoxide Assay Kit measures the hydroperoxides directly utilizing the redox reactions with ferrous ions. An easy to use quantitative extraction method was developed to extract lipid hydroperoxides into chloroform, and the extract is directly used in the assay. This procedure eliminates any interference caused by hydrogen peroxide or endogenous ferric ions in the sample and provides a sensitive and reliable assay for lipid peroxidation. This kit is available in two formats: 100 dtn, which is designed to be read using a single-tube spectrophotometer, and 96 wells, which is designed to be read using a 96-well microplate reader. The 96 well kit contains a special glass plate which is resistant to organic solvents used in the assay, this is the only difference between the two kit types.