The recent cloning of the human enzyme 11beta hydroxysteroid dehydrogenase type 2 (11betaHSD2), and the demonstration of point mutations or deletions in both familial and apparently sporadic cases of apparent mineralocorticoid excess (AME), underlines the importance of this enzyme in excluding glucocorticoids from mineralocorticoid receptors (MR). Although the sodium retention characteristic of AME can thus be explained by absent or very reduced (< 10%) levels of renal 11 betaHSD2 activity, whether or not the enzymatic defect contributes to the elevated blood pressure by mechanisms other than sodium retention remains to be determined.