Brain natriuretic peptide (BNP) was first identified in the porcine brain and later isolated from porcine, rat, and human hearts. In humans, plasma BNP concentrations are progressively elevated with increasing severity of hypertension, particularly when left ventricular hypertrophy (LVH) is present. This presumably reflects increases in ventricular mass associated with increased synthesis and constitutive secretion of BNP from ventricular tissue. In this report, plasma BNP may be a marker for hypertensive LVH. Acute administration of BNP induces significant natriuresis and suppresses plasma aldosterone in hypertensive subjects. However, further studies are necessary to clarify the pathophysiological significance of BNP in essential hypertension.