A patient with acute pancreatitis was treated with peritoneal dialysis and had rapid improvement. At frequent intervals during the dialysis, samples of the patient's blood, urine, and peritoneal fluid were assayed for amylase and lipase. Calculated renal and peritoneal dialysis clearances of these enzymes showed that amylase clearance by the kidney was better than that by peritoneal dialysis; lipase, on the other hand, was more efficiently removed by peritoneal dialysis than by the kidney. A review of the literature on the use of peritoneal dialysis in the treatment of acute pancreatitis is followed by an hypothesis concerning why peritoneal dialysis is so effective in reversing the course of acute pancreatitis.