A severe case of congenital chyloperitoneum was managed over a prolonged period by permanent drainage and replacement of lymphatic loss by fresh frozen plasma, resulting in normal development of the infant. The average daily drainage of 360 ml during a period of a medium-chain-triglyceride (MCT) diet could be reduced to 228 ml (1.58 ml/kg per h) with total parenteral nutrition, representing apparently the basal flow rate of the intestinal lymphatics. Reduction in leakage, however, did not influence the observed lymphocytopenia. Healing of the lesion within the intestinal lymphatic system occurred after a brief period of bacterial peritonitis. The rationale for treatment with an MCT diet and for the application of total parenteral nutrition in infants with chyloperitoneum is discussed.