This article is available online at http://www.jlr.org Supplementary key words stratum corneum • very long chain fatty acids • mono alkyl diacyl glycerol • transepidermal water loss • multiphoton excitation microscopy • lipid mass spectrometryThe acyl-CoA binding protein (ACBP)/diazepam binding inhibitor (DBI) (Entrez Gene ID: 13167) is a 10 kDa intracellular protein that specifi cally binds medium and long chain acyl-CoA esters (C 14 -C 22 ) with very high affi nity (K d ف 1-10 nM) ( 1, 2 ). The protein is expressed in all eukaryotic species and in all mammalian tissues investigated ( 3-5 ); however, expression levels differs markedly between different tissues and cell types examined, with particularly high levels in epithelial cell types and in cells with a high turn-over of fatty acids (FA) ( 6 ). Consistently with this, we have shown that the ACBP gene is activated by lipogenic transcription factors, such as the peroxisome proliferatoractivated receptor ␥ ( 7 ) and members of the sterol-regulatory element binding protein family ( 7-10 ). In vitro studies indicate that ACBP plays a role in transport of acyl-CoA esters and may deliver acyl-CoA esters to phospholipid