The interaction between converting enzyme inhibition and sympathetic system activity at systemic and regional (renal, mesenteric, hindlimb) levels was investigated in adult pithed spontaneously hypertensive rats (SHR) using perindopril (5 mg/kg orally every day for 8 days) and the pulsed Doppler technique. Perindopril induced a decrease in systolic blood pressure and in regional vascular resistance which was abolished by binephrectomy. In addition, the drug had a sympathoinhibitory effect on the systemic vasopressor and the regional vasoconstrictor responses to cirazoline, especially UK 14304, an effect which was kidney-dependent (abolished by binephrectomy) and postjunctional, and spinal cord stimulation, an effect which was kidney-independent and most likely prejunctional in its mechanism.