Infusion of thrombin and the fibrinolysis inhibitor tranexamic acid during ether anaesthesia in the rat gives rise to fibrin deposition in the renal glomeruli. This resulted in renal insufficiency as indicated by an increase in the serum urea nitrogen, reduction in the renal blood flow and patchy cortical necrosis in the kidneys. The plasma renin activity was elevated initially probably due to the ether anaesthesia. Infusion of the angiotensin II antagonist saralasin prevented the renal insufficiency if it was given during the thrombin infusion but not if it was given afterwards. The deposition of fibrin in the kidneys was also reduced. The results indicate that angiotensin II is involved in the pathogenesis of the renal injury.