DNA sequences recognized by the glucocorticoid receptor are termed glucocorticoid-responsive elements because of their stimulatory effect on transcription. An oligonucleotide of 15 base pairs having partial or perfect symmetry is necessary for glucocorticoid induction and this same oligonucleotide is surprisingly also recognized by the progesterone receptor. Here we define a palindromic sequence of 15 base pairs, modelled after a sequence element shared by the vitellogenin genes of frog and chicken, which confers oestrogen inducibility on a heterologous promoter and can be converted into a glucocorticoid-responsive element by substitution of one or two bases at homologous positions in the palindrome. Considered with the observation that the DNA-binding domains of steroid receptors are closely related, this finding demonstrates that the steroid-responsive elements constitute a family of related DNA sequences.