A significant percentage of acute renal failure patients may benefit from a diagnostic renal biopsy, but this procedure carries an unacceptable risk of hemorrhagic complications. We have previously shown that red cell transfusions and 1-deamino-8-D-arginine vasopressin (DDAVP) are effective in managing uremic bleeding. We now report the results of giving washed red cell transfusions or DDAVP to 9 patients with uremia due to acute renal failure to improve hemostasis and allow a diagnostic renal biopsy. All patients admitted to the study had prolonged bleeding time (BT), ie, more than 10 minutes, and our procedure shortened BT in all cases, though in two patients BT after the therapeutic procedure was still longer than normal. In these two, biopsy was not performed. The seven patients whose BT became normal underwent percutaneous biopsy. Only minor clinical complications were registered. Computerized tomography (CT) revealed an incidence of perirenal hematomas comparable to that usually reported in patients with normal or slightly depressed renal function who undergo renal biopsy. Our findings indicate that red cell transfusions or DDAVP can temporarily restore hemostasis, allowing a diagnostic percutaneous biopsy in patients with acute renal failure.