Chylothorax and chylopericardium are rare conditions occurring in infants and children. Both may be traumatic or nontraumatic in origin. We reviewed our experiences with the management of sixteen pediatric cases (10 males, 6 females; 11-days to 14-years old) of chylothorax and chylopericardium from 1997 to 2003. There were fifteen cases of chylothorax (9 left, 2 right, 4 bilateral) and two cases of chylopericardium (1 isolated and 1 associated with chylothorax), and their incidences of occurrence after cardiothoracic surgery were 0.89% and 0.12%, respectively. Of the fifteen cases occurring after cardiothoracic surgery, thirteen patients had corrective or palliative surgery for complex congenital heart disease, and two patients had removal of thymolipoma and neuroblastoma, respectively. Included also in this review was an 11-day old preterm infant with hydrops fetalis and congenital heart disease who developed chylothorax. Characteristics of chylous effusion included a presence of whitish opaque fluid in the pleural cavity and the pericardial cavity, having a triglyceride content ranging from 59 to 1689 mg/dl which was higher than a plasma triglyceride, a protein content of 2.4 to 7.4 g/dl, and a presence of lymphocyte predominance. The average latent period for diagnosis of chylothorax or chylopericardium was 13 days (range 3-30). All patients were treated primarily with nutritional modification using medium-chain triglycerides (MCT) instead of long-chain triglycerides in their diet; and only a few cases needed bowel rest with total parenteral nutrition (TPN). Twelve patients completely responded to a MCT-rich diet; two cases resolved after switching to TPN and another case needed surgery for ligation of lymphatic vessels around the thymus gland. The mean duration of lymph drainage was 12.1 days (range 3-29) and the average length of time of continued conservative treatment (MCT-rich diet and TPN) was 29.8 days (range 18-47). Fourteen patients (87.25%) had good outcome, i.e. resolution from chylothorax or chylopericardium and return to normal diet. Two of the fourteen patients developed severe infections; one was diagnosed with suspected bacterial endocarditis and the other had candidemia. However, both responded well to antibacterial and antifungal drugs, respectively. One case succeeded after surgery. A case that had low compliance with dietary recommendations and required repeated placement of drainage devices died due to infection with enterococcal septicemia. Early and good compliance with MCT-rich diet is essential for achieving a favorable outcome in the management of chylothorax and chylopericardium in children.