The formation and toxicity of trans-4-hydroxy-2-nonenal in the central nervous system is well documented. However, the metabolism of HNE in the central nervous system (CNS) is not clear. HNE metabolism in the CNS appears to be different from that in other tissues and organs and may be dependent on the cell type and subcellular environment. Our data show that HNE metabolism is affected by the stereocenter of HNE and that oxidation of HNE may be a primary route of metabolism. Further metabolic analysis of HNE disposition is needed to clarify which pathways are truly important in normal and pathological states in the CNS.