This review outlines a decade of research that employs quantitative kinetic methods of autooxidation to phospholipids aggregated into membranes. The classical rate law for autoxidation:was found to apply to heterogeneous systems of bilayers and micelles, wherekpand 2kt. are the rate constants for chain propagation and termination, respectively, andRi, the rate of chain initiation, is controlled by thermal initiators. Theoxidizabilityof a typical lipid chain, linoleate 18:2, at 30 °C was similar (0.02–0.04 M−1/2s−1/2) in different media (solution, micelles, bilayers) and for different procedures using water-soluble or lipid-soluble initiators and inhibitors. A reduction in the absolute rate constant for termination, 2ktby a hundredfold in bilayers of dilinoleoylphosphatidyl choline (DLPC) compared to that intert-butyl alcohol solution, and a drop in thekpby a factor of five are interpreted in terms of diffusion of polarized peroxyl radicals from the hydrophobic bilayer phase to the aqueous surface, where peroxyls are strongly solvated by water. Such phenomena may also account for significant changes as observed by31P NMR spectra in bilayer lamellar structure accompanying extensive peroxidation. Analysis of the hydroperoxides formed by peroxidation of mixed bilayers of DLPC + DPPC (16:0) initiated by a water-soluble initiator, azobis(2-amidinopropane•HCl) (ABAP), showed a linear trend between the ratio ofcis,transtotrans,transgeometrical isomeric hydroperoxides and [DPLC] consistent with a peroxidation mechanism proposed in homogeneous solution.The antioxidant activities,kinh, of three classes of antioxidants: (a) polyalkyl-6-hydroxychromans (e.g., vitamin E), (b) polyalkyl-4-methoxyphenols, and (c) trialkylphenols, were measured in DLPC membranes. The results show an overall leveling and depression ofkinhvalues in DLPC membranes in the series (a) (by several orders of magnitude), (b), and (c) compared to known values in solution in chlorobenzene. In aqueous bilayers it is proposed thatkinhvalues are attenuated by hydrogen bonding by water at both theparaether oxygen and phenolic groups. Restricted diffusion (e.g., of α-tocopherol) may also reduce antioxidant activities in membranes. A synergistic effect between ascorbic acid and α-tocopherol was discovered under conditions of inhibited peroxidation of linoleate in SDS micelles. The natural peptide glutathione, GSH, however, acts as aco-antioxidantwith vitamin E by trapping peroxyls in the aqueous phase.Solid cholesterol was found to partition directly into PC lipsomes by shaking, above or below the phase transition temperature, and membrane-bound cholesterol, unlike the solid, undergoes facile peroxidation. A water-soluble form of α-tocopherol complexed with bovine serum albumin (α-toc:BSA) is an effective antioxidant for autoxidations of linoleate in SDS micelles. In contrast, α-toc:BSA required a long equilibration time (e.g., 12 h) with liposomes (DLPC) before the α-tocopherol was transferred to the liposomes to provide effective antioxidant action.