1. Acute renal failure was produced in rats by intramuscular injection of glycerol. Subsequently, changes in the concentrations of renin and of angiotensin II in plasma and the renin content of the kidneys were followed.
2. At 4 and 8 h after glycerol administration, plasma renin and angiotensin II had increased two-to three-fold; they remained elevated for 48 h and then returned towards normal. At 7 days, the values were still slightly raised.
3. At 4 and 8 h after glycerol injection, kidney renin had decreased but it had increased after 24 and 48 h.
4. Passive immunization with angiotensin II antibodies, given at the time of glycerol injection and 2 and 4 h afterwards, prevented the development of acute renal failure. When angiotensin II antiserum was administered later (8, 10 and 12 h after glycerol) it had no effect.
5. Stimulation of the renin-angiotensin system may be involved in the pathogenesis of the early phase of acute renal failure.