The nuclear orphan receptors RORalpha and RORgamma are members of the nuclear hormone receptor superfamily. This family acts by directly associating with DNA sequences known as hormone response elements (HREs) and typically binds DNA as either homo- or heterodimers. RORalpha and RORgamma are unique in that they bind DNA as monomers. RORalpha has multiple isoforms that share common DNA- and putative ligand-binding domains, but differ in their aminoterminal domains, which are generated by alternative RNA processing. RORgamma comprises a 560 amino acid protein that shares 50% amino acid identity with RORalpha and is most highly expressed in skeletal muscle. Although these proteins are considered