Recent observations suggest that the syndrome of mineralocorticoid excess, primary aldosteronism, may be more common than has been previously believed. Enhanced detection of this syndrome has been simplified by the development of sensitive screening techniques. The diagnosis and differentiation of several different forms of primary aldosteronism have also been improved by new insights into the pathophysiology of these disorders and the application of several new techniques to distinguish them. The discovery of variable activity of several steroids on the mineralocorticoid receptor has provided additional understanding of the finding of the manifestations of hyperaldosteronism in the presence of normal aldosterone production. Finally, new approaches to the treatment of primary aldosteronism have also been developed.