1. Hypertension was induced in rats by renal artery clip with the contralateral kidney removed (Goldblatt I) or left intact (Goldblatt II).
2. Plasma noradrenaline was increased 62% in the Goldblatt I animals after 3 weeks.
3. Hypothalamic tyrosine hydroxylase and dopamine β-hydroxylase activities, and the concentration of noradrenaline were increased in the Goldblatt I animals after 3 weeks.
4. Enhanced hypothalamic noradrenaline synthesis may be a pathogenic factor in Goldblatt I renovascular hypertension.