9-OxoODE results from oxidation of the allylic hydroxyl of either 9(S)- or 9(R)-HODE. Rabbit reticulocyte plasma and mitochondrial membranes contain both 9- and 13-oxoODEs, representing about 2% of the total linoleate residues in the membranes. Most of these oxidized linoleate residues are esterified to membrane lipids.