Membrane phospholipids contain polyunsaturated fatty-acid side chains esterified to phosphoglycerol. These polyunsaturated fatty acyl esters are easily oxidable lipids. A sensitive method for determination of lipid peroxidation is of considerable interest. Usually lipid peroxidation is determined by evaluation of a by-product, malondialdehyde, which is produced by lipid-peroxide breakdown. Malondialdehyde, however, does not represent the early stage of membrane lipid peroxidation nor the true amount of oxidized lipids. Moreover, most techniques for malondialdehyde use thiobarbituric acid-reactants evaluation (1), which is an indirect measurement.