sure in hypertensive emergencies, nitroprusside is still considered the drug of choice because of its rapid onset of action, short serum half-life, and long history of efficacy.6 The major disadvantage of nitroprusside is the conversion to its very toxic metabolites, cyanide and thiocyanate. This problem is often manageable by limiting the dose and duration of infusion. Despite shortterm, low-dose administration, however, nitroprusside has been associated with deterioration in renal,2-5 cerebral,7-9 and cardiac'0 function.Fenoldopam mesylate is a novel vasodilator that acts by dopamine-1 receptor activation." Its vasodilatory actions are greatest in the renal bed, but resistance in other vascular beds (especially splanchnic, coronary, and cerebral) is also reduced.'2 Previous work in normal subjects13 and in mildly hypertensive patients14 has shown that, during fenoldopam infusion, the lowering of blood pressure is accompanied by enhanced renal blood flow. Natriuresis, diuresis, and an increase in the glomerular filtration rate (measured either as inulin or creatinine clear-