1. To examine the importance of angiotensin II formation in the production of frusemide's acute peripheral venous and arterial responses, the effect of pretreatment with captopril was studied.
2. Captopril abolished the acute increases in venous capacitance and blood pressure and attenuated the increases in forearm vascular resistance produced by intravenous frusemide.
3. The study provides evidence that angiotensin II formation performs an essential role in the production of the acute vascular effects of frusemide in man.