Most people with consistently high blood pressure have “essential” hypertension, a physician's term for “no known cause.” Over the last 20 years, however, studies have shown that ∼1 in 10 patients do have an identifiable cause. Such patients overproduce the adrenal steroid hormone aldosterone (primary aldosteronism), which raises blood pressure and promotes sodium retention and potassium excretion. On page 768 of this issue, Choi et al. report two different mutations in the gene encoding the potassium channel KCNJ5 in patients (8 of 22) with an aldosterone-producing adrenal adenoma (APA). A third mutation in the same gene is also identified in a father and two daughters with florid adrenal hyperplasia, a hereditary condition that is treated by removing the adrenals in early childhood. The findings have implications for understanding adrenal physiology and pathology.