1. Experiments in rabbits confirmed that natriuresis induced by a continuous 2-h intravenous infusion of angiotensin is temporary and declines after 1 h. A similar transient increase in magnesium and calcium excretion occurred. Glomerular filtration rate (GFR) and blood pressure fell towards the end of the angiotensin infusion.
2. This pattern of response was not influenced by prior adrenalectomy or by replacement of water lost in the associated diuresis, but water replacement accompanied by partial replacement of lost sodium resulted in a sustained natriuresis and better maintenance of GFR.
3. Transience of the natriuretic response was not peculiar to angiotensin, since continuous intravenous infusion of five other natriuretic agents produced the same effect, together with progressive reduction of GFR and blood pressure.
4. An increase in angiotensin infusion rate after 1·5 h produced a further temporary natriuresis.
5. It was concluded that neither aldosterone nor water loss are primarily responsible for the decline in natriuresis after 1 h during angiotensin infusion, but that a progressive fall in GFR, aggravated by sodium loss, is the most likely mechanism.