PURPOSE: Congenital chylothorax is an accumulation of lymphatic fluid within the pleural space. It is a common cause of unidentified hydrops fetalis. We examined the perinatal history, clinical manifestation, diagnosis, treatment, and outcome in 6 newborns diagnosed to have congenital chylothorax with hydrops fetalis. We also studied the effect of octreotide therapy for congenital chylothorax in relation to conservative treatment. METHODS: We retrospectively reviewed the medical records of 6 patients diagnosed to have congenital chylothorax with hydrops fetalis among 27,907 newborns who were born at the Cheil General Hospital and Womens Healthcare Center between January 2004 and July 2007 . The diagnosis of chylothorax is based on the analysis of pleural fluid before and after milk feeding. RESULTS: Incidence of congenital chylothorax in this study was 0.021%. All 6 cases were noted in over the 92% lymphocyte in pleural analysis. Transudate was changed into chyle with increasing triglyceride levels above 200 mg/dL after milk feeding. Three of 6 infants improved with conservative treatment, including thoracostomy and assisted ventilation. The others had persistent symptoms despite conservative treatment and responded to octreotide therapy. A complication, specifically vomiting was noted in 1 case during octreotide therapy. CONCLUSION: In this study, octreotide therapy resulted in a safe and excellent outcome. Therefore, octreotide therapy is considered in severe refractory congenital chylothorax in conservative treatment. Further studies are required to determine appropriate guidelines for octreotide therapy.