Acute renal failure is a rare complication of acute pyelonephritis in patients without urinary obstruction. Although urinary tract infections are common in adults, pyelonephritis is rarely con-sidered in the differential diagnosis of acute renal failure nor is renal failure considered a likely consequence of bacteriuria. Only few cases of acute renal failure due to acute pyelonephritis have been reported in the literature. Herein, we reported a case of acute pyelonephritis compli-cated with acute renal failure.(J Urol R.O.C., 9:208-210,1998)