1. Potassium was infused intravenously in an incremental fashion and the plasma aldosterone responses were measured in conscious beagle dogs at five different intakes of dietary sodium.

2. Potassium/aldosterone dose—response curves were constructed for each dietary sodium regimen.

3. The rate of increase of plasma potassium during graded potassium infusion became progressively greater with increasing sodium depletion.

4. Regression lines of plasma aldosterone on plasma potassium were progressively elevated and steepened with increasing sodium depletion.

5. The alteration of these dose-response curves could in part have been the result of chronic elevation of plasma potassium and angiotensin II, and depression of plasma sodium, with sodium deprivation.

6. By contrast, acute changes in plasma angiotensin II or sodium concentrations across incremental infusions of potassium did not explain the progressive changes in the potassium/aldosterone dose—response curves.

7. The steepest part of the plasma aldosterone response curve was in the plasma potassium range 4–6 mmol/l.

8. Maximum achieved aldosterone levels were similar to or greater than those attained during angiotensin II infusion in previous studies in beagle dogs.

9. Potassium, like angiotensin II and adrenocorticotropic hormone, becomes a more effective stimulus to aldosterone with sodium depletion, thereby facilitating the preservation of sodium homoeostasis.

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