The relationship between elevated water intake and oedema associated with congestive cardiac failure in the dog.

1. In the dog constriction of the thoracic region of the inferior vena cava increases water intake and extracellular and plasma fluid volumes. 2. Restriction of water intake to the pre‐operative level for 2 weeks reduces the measured extracellular fluid volume to the pre‐operative level. 3. Administration of the competitive angiotensin inhibitor, saralasin acetate, to two dogs in congestive cardiac failure following thoracic caval constriction markedly reduced their water intake. 4. These results suggest that increased fluid intake is probably important in the aetiology of the oedema associated with congestive cardiac failure, probably through the renin‐angiotensin system.