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1 In this study the renal selectivity of dopamine and its prodrugs L-dopa and gludopa, with respect to their effects on regional blood flow, vascular resistance and central haemodynamics was investigated in normal rats and in rats with glycerol-induced acute renal failure (ARF). 2 In normal, anaesthetized rats, dopamine as well as its prodrugs caused a dose-dependent reduction of vascular resistance in the kidney (RR), mesentery (MR) and hindquarters (HQR) (dose range: dopamine: 0. 1-5 ftmol kg-' h-i; L-dopa and gludopa: 1 -200 pmol kg'-h-'). Blood pressure and heart rate were affected at the highest dose only. 3 Administration of glycerol induced a preferential renal vasoconstriction; renal blood flow (-60%) and vascular resistance (+ 190%) were significantly more affected than MR (+40%) and HQR (+ 60%). This was only ameliorated by a low rate (10 pmol kg-' h-') infusion of gludopa: the glycerolinduced reduction of renal flow and increase in RR were significantly attenuated. A high dose of gludopa (100 gmol kg-' h-') or any dose of L-dopa or dopamine did not induce this beneficial effect. The glycerol-induced increase in MR and HQR was not attenuated by any of the treatments used. 4 The results indicate that gludopa is not renally selective at a pharmacodynamic level in normal, anaesthetized rats. Contrary to this, a low dose of gludopa does cause a renal selective vasodilatation and reduction of RR in rats with glycerol-induced ARF. This difference could be explained by a difference in renal vascular tone between normal rats and glycerol-induced ARF rats. A high dose of gludopa does not cause these renal-selective effects: renal resistance and renal flow are at the same level as following glycerol and saline. This is probably due to the systemic effects of the released dopamine.