A recombinant full length human glucocorticoid receptor stimulates transcription in vitro of test genes containing synthetic glucocorticoid and progesterone response elements or murine mammary tumor virus promoter. The receptor expressed in a baculoviral vector is highly active, enhancing transcription of hormone response genes greater than 30-fold even at a receptor concentration of 1.2 nM. The enhancement of transcription is glucocorticoid and progesterone response element-dependent, suggesting that it is a receptor mediated event. In vitro and in vivo treatment with the agonist dexamethasone or with the antagonist Ru486 did not alter significantly the functional activity of partially purified receptor. Kinetic studies suggest that both glucocorticoid receptor and HeLa cell extracts are required for formation of a stable committed transcriptional complex. Our results indicate that the action of glucocorticoid receptor on gene transcription is similar to that defined recently for the progesterone receptor and may be a general mechanism for all steroid receptors.