Intrarenal perfusion of dopamine (6 mug/kg/min for 10 min) caused a significant increase of renin secretion, together with a significant increase in renal blood flow. This renin hypersecretion is not accompanied by any significant alteration in renal perfusion pressure, kalemia or natriuresis. The role of intrarenal dopaminergic receptors has been studied: (a) Haloperidol (intrarenal perfusion of 50 mug/kg/min for 20 min) suppresses the renal vasodilation and renin hypersecretion induced by dopamine. (b) Propranolol (intrarenal perfusion of 1 mg/kg in 15 min, then of 4 mg/kg/hr) alters neither the renal vasodilation nor the renin hypersecretion induced by dopamine. These observations support the assumption that the dopaminergic receptors are brought into play in the two renal responses to dopamine studied by us.