Currently, studies on renal mineralocorticoid and glucocorticoid receptors have been confined to experimental animals. In experiments made upon human kidneys removed at operation, tritiated aldosterone has been shown to bind specifically to a single class of cytoplasmic sites which show steroid specificity requisite for physiological mineralocorticoid receptors. Tritiated dexamethasone, similarly, binds specifically to a single class of cytoplasmic sites with affinity characteristics appropriate for glucocorticoid receptors. The similarity between the human renal receptor profile for adrenocorticoids and that found in experimental animals may validate cautions extrapolation from animal models of adrenocorticoid effector mechanisms to man.