Nuclear receptors regulate transcription by binding to DNA-response elements using their conserved DNA-binding domains. These response elements contain conserved hexameric sequences that can be arranged in various bipartite configurations, including inverted and direct repeats. A series of structural studies on receptor--DNA binding complexes illustrate the strategies used by receptors to recognize the symmetry of their binding site as well as its sequence. These structures also indicate how cooperation between receptors enhances their joint affinity and selectivity for correctly configured sites.