1. Infusion of angiotensin II into dogs at constant dose over 2 weeks caused a progressive rise in arterial pressure.
2. When the infusion was stopped the pressure dropped slowly from hypertensive levels over 48 h.
3. Dose—response studies at weekly intervals showed progressive elevation, without steepening, of the plasma angiotensin II—blood pressure curve.
4. Thus, during prolonged administration of angiotensin II, a given plasma concentration of the peptide can sustain a higher arterial pressure than it can during acute infusions.