1. We describe a new method of producing two-kidney hypertension in dogs by a two-step procedure with complete occlusion of a renal artery 2 weeks after it was partially constricted.
2. Control mean arterial pressure (96 ± 3 mmHg) of nine conscious, trained dogs rose to 107 ± 3 mmHg 2 weeks after partial constriction of a renal artery, and it stabilized at a sustained hypertensive plateau (124 ± 7 mmHg) 3 weeks after complete occlusion.
3. Intravenous infusion of an angiotensin II antagonist (Sar1-Thr8-angiotensin II) caused arterial pressure to fall during the acute but not the chronic phase of renal hypertension. In this latter phase plasma renin activity had returned to control values.
4. We conclude that the renin—angiotensin system appears not to be directly involved in the chronic phase of two-kidney hypertension in the dog.