Oxidation of Fe2+ in the presence of peroxidized lecithin-liposomes small unilamellar vesicles suspended in various media (pH = 5.5) is described. Peroxidation of lecithin was induced by UV light and assayed by three methods: estimation of conjugated dienes, accumulation of hydroperoxides and by the thiobarbituric acid test. The oxidation of Fe2+ was accelerated by phosphate and citrate buffers, but in acetate buffer it was dependent on lipid peroxidases concentration and exhibited saturation kinetics.