The aim of this work was to evaluate the use of 1 m2 Cuprophan hollow fiber filters for continuous arteriovenous hemodialysis procedures. Thirty one critically ill patients (18 male) aged between 20 and 80 years old, subjected to 35 hemodialysis procedures were studied. Sixteen patients had acute renal failure (10 of these had multiorgan failures) and 15 terminal chronic renal failure. Femoral vessels were used for vascular access and isotonic peritoneal dialysis solution flowing at 16.6 ml/seg as dialyzing solution. No extracorporeal pump assistance was used. Mean procedure time was 76 +/- 69.7 h, filter consumption was 2.8 +/- 2.1 filters/procedure, ultrafiltration rate was 168 ml/min and urea clearance was 19.9 +/- 4.4 ml/min. No replacement solutions were required and good electrolyte and circulating volume control was achieved with excellent hemodynamic stability. Blood urea fell from 116.9 +/- 49.1 to 64 +/- 27.2 mg/dl after the procedure (p < 0.001). Hyperglycemia was observed in eight procedures, six patients developed non infectious vascular access complications and two patients catheter related sepsis. We conclude that continuous arteriovenous hemodialysis using cuprophan membranes is a good renal substitution technique for critically ill patients.