This paper therefore, reviews current knowledge of the role of renal dopaminergic activity in essential hypertension. This is believed to be one of the most important renal diuretic and depressor systems. Suppression of urinary excretion of free dopamine (DA) is observed in essential hypertensives, particularly in those with low plasma renin activity (LRH) who demonstrate body fluid volume expansion. An increased natriuretic response to exogeneously administered DA is found, particularly in LRH, and suppressed biosynthesis of DA from L-dopa in the kidney has been suggested. Furthermore, this suppression of renal dopaminergic activity was also observed in young normotensive subjects with an apparent family history of hypertension before any evidence of hypertension emerged. From these findings, it is concluded that the decrease in renal dopaminergic activity is involved, at least in part, not only in the pathophysiology of essential hypertension, but also in the pathogenesis of this disease.(Jpn Heart J 1996; 37: 815-828)