Thirteen patients with acute renal failure after mayor surgery were treated with CAVH, 6 children after liver transplantation (OLT) and 7 after extracorporeal cardiac surgery (ECS). The ages ranged from 4 months to 19 years, with filters from 0.16 m2 to 0.5 m2, according to the weights. CAVH was initiated 19 hours (mean) after OLT and 10.5 hours (mean) after ECS. Mean creatinine clearance was 6.3 ml/min/1.73 m2 (ECS) and 10.1 ml/min/1.73 m2 (OLT). Serum creatinine remained under acceptable values (mean 2.1 mg.%) in both groups. Mean fluid removal was 5.7 L/day (242 ml/kg/day), which allowed plasma administration despite oligoanuria in the OLT group. Fluid removal decreased central venous pressure (p < 0.001) and increased mean arterial pressure (p < 0.01) in the ECS group, and inotropic support could be diminished. CAVH was well tolerated and it was maintained for 79 hours (ECS) and 105 hours (OLT).