In recent years, the study of monogenic forms of hypertension has added greatly to our understanding of the regulatory mechanisms affecting blood pressure. Recently, a novel such form of human hypertension caused by gain-of-function mutation in the mineralocorticoid receptor, the mediator of aldosterone-induced sodium transport in the distal nephron, has been described, with the notable finding being that pregnancy causes a severe worsening of blood pressure. In this review, the mechanism by which the mutation causes hypertension, and the implications these findings have for improved understanding of cardiovascular physiology and mineralocorticoid receptor biology, are discussed.