Sodium pentobarbitone anaesthetised Wistar rats were prepared for the measurement of renal blood flow, close renal-arterial infusion of drugs and electrical stimulation of the renal nerves. Administration of intra-renal arterial bolus doses of noradrenaline, phenylephrine, methoxamine and renal nerve stimulation caused transient dose- or frequency-related reductions in renal blood flow, ranging from 20% to 85%, with all slopes being significant (P < 0.05-0.01). Intra-arterial infusion of BRL38227 for 30 min at 0.5 micrograms/kg per min had no effect on blood pressure but at 0.75 and 1.0 micrograms/kg per min there were reductions of 9 mm Hg (P < 0.05) and 19 mm Hg (P < 0.01), respectively. The slopes of the dose-response curves for noradrenaline, phenylephrine and methoxamine and frequency-response curves for renal nerve stimulation generated at each dose level of BRL38227 could not be distinguished statistically. The findings of this investigation suggest that the adrenergic control of renal haemodynamics would occur normally in the presence of hypotensive doses of BRL 38227.