1. Plasma noradrenaline was measured in groups of rats up to 4 weeks after application of a renal artery clip.
2. When renal artery clipping was accompanied by contralateral nephrectomy (one-kidney model) plasma noradrenaline was significantly higher in hypertensive rats than in sham-operated control rats at 7, 14 and 28 days.
3. Plasma noradrenaline was not altered at any time examined in the two-kidney model (unilateral clip and contralateral kidney left in situ).
4. Neurogenic mechanisms mediated by the peripheral sympathetic nervous system appear to participate in the development of one-kidney renovascular hypertension, but do not play a significant role in the two-kidney model.