1. Serial changes in plasma renin activity and plasma angiotensin levels were followed in rats during acute renal failure induced by mercuric chloride or glycerol.
2. During mercuric chloride-induced acute renal failure there were transitory large increases in plasma renin and angiotensin. In contrast, rats with acute renal failure produced by glycerol had a reduction in plasma renin and angiotensin levels at 1 h, after which the levels returned to control values.
3. There was no correlation between the systemic changes in plasma renin and angiotensin and the mortality from or severity of the renal failure.
4. Passive or active immunization of rats to angiotensin afforded no protection against renal failure associated with either glycerol or mercuric chloride.
5. It is concluded that the renin-angiotensin system plays no direct systemic vasoconstrictor role in the production of acute renal failure in these experimental models in rats.
