During a period of 3 years 27 patients in acute renal failure (ARF) due to peritonitis underwent pump driven continuous hemofiltration (PDHF). PDHF caused neither hemodynamic nor metabolic disturbances, which in contrary are frequently seen during intermittent hemodialysis treatment in septic patients. BUN and creatinine levels fell significantly (p less than 0.001) and remained at 60 mg% and 2.0 mg%, respectively (mean values). Severe coagulation disorders occurred in 5 patients; in 2 patients PDHF was continued under protamine administration into the venous line, in 3 patients PDHF was stopped for 24 hours and than started again. Bleeding stopped in all cases, therefore surgery was not necessary. Other major complications of PDHF were not observed. Kidney function recovered in 44.4% of patients, and mortality was 70.4%. This is clearly lower than in abdominal septic patients under intermittent hemodialysis. Despite much higher costs (2.5 times the costs of hemodialysis treatment per day) PDHF seems to be a promising alternative in the treatment of ARF complicating septic multiple organ failure.