BACKGROUND/PURPOSE Chylothoraces have been reported rarely after congenital diaphragmatic hernia (CDH) repair, but that is contrary to the authors' experience. The aim of this study was to audit the outcome of antenatally diagnosed CDH cases to determine the incidence, possible risk factors, and morbidity associated with chylothorax in CDH patents. METHODS Twenty-four of 35 consecutive infants with CDH (69%) underwent surgical repair and survived the immediate postoperative period. RESULTS Effusions developed in all 22 for whom chest radiographs were available. Six of the eight infants whose effusions required drainage had a chylothorax. Those six infants required a mean of 8 days of thoracentesis, during which a mean total volume of 358 mL/kg of fluid was removed. The infants remained on a medium-chain triglyceride (MCT) formula for a mean of 81 days. The six infants with a chylothorax differed from the rest with respect to their duration of oxygen dependence (a median of 28.5 versus 15 days, P < .05) and hospital stay (a median of 5.5 versus 4 weeks, P < .05), but no significant risk factors for the development of a chylothorax were identified. CONCLUSION Chylothorax is a relatively common cause of effusion after CDH repair and is associated with increased morbidity.