The nuclear hormone receptors constitute a large family of transcription factors. The binding of the hormonal ligands induces nuclear receptors to assume a configuration that leads to transcriptional activation. Recent studies of retinoic acid and thyroid hormone receptors revealed that, upon ligand binding, a histone deacetylase (HDAC)-containing complex is displaced from the nuclear receptor in exchange for a histone acetyltransferase (HAT)-containing complex. These observations suggest that ligand-dependent recruitment of chromatin-remodeling activity serves as a general mechanism underlying the switch of nuclear receptors from being transcriptionally repressive to being transcriptionally active.