The retinoid X receptors (RXRs) are nuclear receptors that mediate the biological effects of retinoids by their involvement in retinoic acid-mediated gene activation. RXRα is the dimerization partner for the type II nuclear receptors that includes the liver X receptor (LXR). The LXR receptor is activated by oxysterol ligands and forms a heterodimer with RXR. After heterodimerization LXR initiates transcription of target genes by binding to the LXR response element. LXR/RXR is involved in the regulation of lipid metabolism, inflammation, and cholesterol to bile acid catabolism. Genes regulated by LXR include the ATP-binding cassette transporter A1 (ABCA1), which effluxes cholesterol from extrahepatic cells, the sterol regulatory element binding protein-1c (SREBP-1c), AIM and LPL.