The syndrome of juxtaglomerular hyperplasia with hypokalemic, hypochloremic alkalosis, aldosteronism, hyperreninemia, and normal blood pressure may be familial, and is probably inherited as a recessive trait. It can usually be distinguished from salt-losing chronic glomerulo-nephritis by the histologic appearance of the kidneys, and by the absence of sodium "leak" with a low-sodium intake. Urinary, and thus renal, prostaglandin E is increased in the untreated patient: when this is lowered with prostaglandin synthetase inhibitors, the plasma renin and aldosterone decrease, and the plasma potassium concentration rises. These and other results suggest a partial control of renin secretion by prostaglandin E, and also suggest that prostaglandin E is an essential feature of the syndrome; it may, indeed, be a "proximal" cause of all the essential features.