There is increasing evidence that oxtdatively modified low-denstty lipoprotems (LDL) play an important role during atherogenesis (1). LDL oxidation can be mltiated by reactive oxygen species and is accompanied by characteristic changes in all of the major lipid subclasses as well as the apolipoprotein moiety of the LDL particle. These changes do not occur simultaneously, but rather at different time scales as a result of initiation and propagation of the peroxidation cycle and subsequent decomposition of primary lipid-peroxidation products. Therefore, a method applied at a given time point may give different results if applied at another time. The different techniques described here for the measurement of lipid and protein modification (for review, seerefs. 2-5) include measurement of thiobarbituric acid reactive substances (TBARS), conjugated dienes, lipid hydroperoxides by photometric or high-performance liquid chromatography (HPLC) methods, consumption of polyunsaturated fatty acids (PUFAs) and antioxidants, cholesterol oxidation products, aldehydes, or oxygen uptake during LDL oxidation The degree of protein modification is usually assessed by agarose gel electrophoresis, photometric measurement of free ɛ-amino groups, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), or more advanced analytical techniques, e.g., electrosprayliquid chromatography-mass spectrometry (LC-MS). More recently, a variety of different enzyme-linked immunosorbent assay (ELISA) procedures utilizing monoclonal antibodies (MAbs), which were generated toward oxidationspecific epitopes in apo B-100, have been established. [ABSTRACT FROM AUTHOR]