1. The intrarenal role of angiotensin II in the recovery of urinary concentration after frusemide was examined in anaesthetized dogs by the intrarenal infusion of angiotensin II antagonists.
2. Renin secretion and renal inner medullary blood flow (tissue clearance of intraparenchymatously injected 133Xenon) were simultaneously measured before and 3 h after frusemide injection.
3. Intrarenal angiotensin II blockade delayed the recovery of urinary osmolality after frusemide.
4. An inverse relationship was found between renin secretion and renal inner medullary blood flow.