Steroid hormones regulate cellular differentiation and physiologic functions predominantly through gene transcription. Regulation is achieved by the interaction of specific steroid receptor proteins and target genes. Expression cloning techniques were used to select human glucocorticoid receptor complementary DNA clones in order to define the mechanism by which the receptor exerts its transcriptional control. Immobilized fusion proteins from individual clones were used to select epitope-specific antibody which was subsequently eluted and identified by binding to protein blots of cellular extracts. Three cross-hybridizing clones containing inserts expressing antigenic determinants of the human glucocorticoid receptor were isolated.