Acute renal failure (ARF) in newborns and infants is a serious postoperative complication. Peritoneal dialysis is considered the treatment of choice, but is often impossible postoperatively. In adult patients or older children, continuous arteriovenous hemofiltration (CAVH) has been established for 10 years. In 1985, Ronco published case reports on four newborn infants treated with CAVH using a specially designed hemofilter. In between, a few more case reports have been published. We report a case of postoperative septic ARF in an 8-week-old girl with a body weight of 4000 g. We used the Minifilter (Amicon Corp.) connected to a femoral arterial Shaldon catheter and initially a central venous line, later a subclavian Shaldon catheter. Intermittent hemodialysis without ultrafiltration was performed as well. With ultrafiltration rates of 2 to 24 ml/h, mean 12.8 ml/h, we achieved an impressive loss of weight and the pulmonary function improved. The baby died on the 5th day of CAVH treatment of septic multiorgan failure. Even though the small patient did not survive, we demonstrated the feasibility of the method in newborns. CAVH is recommended for overhydrated babies with oligoanuric ARF, but it is not sufficient as a substitute for dialysis in these patients.