Monogenic mutations leading to excessive activation of the mineralocorticoid pathway result, almost always, in suppressed renin and hypertension in adult life and sometimes in hypokalaemia and alkalosis, which can be severe. In most of these syndromes, precise molecular changes in specific steroidogenic or effector genes have been identified, permitting appreciation of (1) pathophysiology, (2) great diversity of phenotype and (3) possibility of genetic methods of diagnosis. Yet to be achieved elucidation of the genetic basis of familial hyperaldosteronism type II, the most common and clinically significant of them, will enhance detection of primary aldosteronism, currently the commonest specifically treatable and potentially curable form of hypertension. While classic, complete-phenotype presentations of monogenic forms of mineralocorticoid hypertension are rarely recognised, more subtle genetic expression causing less florid manifestations could represent a significant proportion of so-called 'essential hypertension.'