ACUTE RENAL FAILURE is a major complication of transfusion reaction. It occurs with significant frequency and carries a high mortality despite progress in modern therapy. This study was designed: (1) to produce acute renal failure in experimental animals under conditions simulating clinical situations, (2) to investigate certain aspects of hemodynamics of transfusion reactions leading to such a lesion, and (3) to explore methods and means of prevention of acute renal failure resulting from the transfusion of incompatible blood. Method Combination of renal ischemia and some nephrotoxin (heme pigment) in the pathogenesis of acute renal failure has been well documented. We used dogs as experimental animals. Hemorrhagic shock and anaphylactic reactions were chosen to effect renal ischemia, and discarded human blood was selected as the nephrotoxic substance. Acute Renal Failure Following Hemorrhagic Shock and Incompatible Transfusion.— As previously reported, 1 a number of dogs were bled rapidly (30 to 40 cc/kg)