1. Renin release from an intact, innervated kidney and from the contralateral denervated kidney was measured before and during a period of suprarenal aortic stenosis.
2. Aortic stenosis of 10 min duration reduced renal perfusion pressure to 50 mmHg and increased renin release from both kidneys, but the response from the innervated kidney was greater.
3. A study of the time-course of the response during 30 min of aortic stenosis showed that the difference in rate of renin release between the innervated and the denervated kidney is greatest during the first few minutes of aortic stenosis.