SK & F 38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine) is a new dopamine receptor agonist which selectively increased renal blood flow when administered i.v. to dogs at cumulative doses of 3.3-1333 microgram/kg. Consistent changes in arterial blood pressure heart rate and cardiac output were not observed. The renal response, which was mediated locally in the kidney, was not antagonized by adequate blocking doses of atropine, propranolol, metiamide and/or mepyramine nor by reserpinization or treatment with indomethacin. It was inhibited, however, by the selective peripheral dopamine receptor antagonist, bulbocapnine. Perhaps as a result of its action on renal blood flow, SK & F 38393 produced a diuresis in normally hydrated rats which was characterized by an increased excretion of sodium, potassium and chloride and a increased urinary pH. Compounds of this type may be useful in better defining dopaminergic receptors and in the treatment of disease states where renal ischemia is present.