Important parameters of lipid peroxidation (LPO) such as fatty acid loss, formation and accumulation of conjugated dienes, lipid hydroperoxides, short-chain alkanes, F₂-isoprostanes, oxysterols, TBA-reactive substances (TBA-RS), malon-dialdehyde (MDA), 4-hydroxynonenal (HNE), and protein carbonyls are described. Assays for the quantification of these parameters are compared. No method for qu-antification of LPO is the ideal assay. A combination of different assays is recommended for evaluation of oxidative stress and LPO in complex biological systems. Examples for clinical applications are presented. A future strategy seems to be the use, optimization, and development of assays for LPO-derived protein and/or DNA changes.