An analysis of receptor mechanisms of glucocorticoid and antiglucocorticoid effect was made. The limiting link in glucocorticoid and antiglucocorticoid realization are specific cytoplasmic glucocorticoid receptors (GR) which function is controlled by heat shock protein (HSP) of 90 kD molecular weight. Under the influence of glucocorticoids (G), GR are released from GR-HSP complex, forming GR-G complexes. The latter are translocated into cell nucleus activate the function of genetic apparatus, change biosynthesis of specific enzymes realizing intracellular glucocorticoid effect Receptor mechanism of antiglucocorticoid effect is realized via competition of steroid and non-steroid drugs with glucocorticoids for binding sites on GR or pharmacological stabilization of GR-HSP complex, decreasing 4SGR release, 4S GR-G forming, and 4SGR-G translocation into cell nucleus. New data about GR chemical structure according to which GR contain 3 functional domains, characterized by regulatory DNA-binding and ligand-binding activity promote researches of antiglucocorticoids. It promoted synthesis of a new most active receptor antiglucocorticoid RU-486 (19-norsteroid), that inhibits ovalbumin and conalbumin synthesis induced by glucocorticoids.