To find the optimal exchange volume and dialysate flow rate for use in peritoneal dialysis, 24 adult patients with acute or acute on chronic renal failure were studied. Based on the exchange volume and duration of one cycle, patients were randomly divided into 4 equal groups. Peritoneal clearances for urea and creatinine were calculated at 2, 8 and 14 hours during dialysis. Increase of dialysate flow rate improved the peritoneal clearance of various solutes, and for the same flow rate 2 liter exchange volume gave better results than 1 liter exchange volume.