The objective of this paper is a retrospective study of all infants treated for congenital chylothorax at the Royal Children's Hospital (RCH), Melbourne, Australia and King Fahad National Guard Hospital (KFNGH), Riyadh, Kingdom of Saudi Arabia. The charts of all infants with congenital chylothorax admitted to RCH over a period of 13 years, June 1982-August 1994, and admissions to KFNGH over a 7-year period, June 1992-August 1998 inclusive, were reviewed including management outcome and complications. There were 19 infants, 13 from RCH and 6 from KFNGH; 11 females and 8 males. Three infants were managed antenatally. Fifteen infants presented immediately after birth. Seven were born with hydrops fetalis, 6 infants had syndromes and 10 infants were born prematurely. Regular infant feeding formula and/or breast milk were used successfully in 12 infants, while in 7 infants medium chain triglycerides (MCT) rich formula was used. Sixteen infants were mechanically ventilated with 75% of them ventilated for < or = 28 days. Fifteen infants received total parenteral nutrition (TPN), and in 80% for < or = 32 days. Hydropic infants had longer duration of mechanical ventilation and hospital stay with mean (range) of 33.9 (3-120) and 115 (23-225) days, respectively, compared with 18 (1-62) and 34.3 (14-88) days for nonhydropic infants. Five infants underwent surgery with failure in four. Sepsis and bronchopulmonary dysplasia were the main complications. The survival rate was 100% regardless of the mode of therapy. The prognosis of Isolated congenital chylothorax in term, and preterm infants is good even in the presence of hydrops. Breast milk and/or regular infant feeding formula should be used initially before proceeding to MCT-rich formula, which may be necessary in some cases. Surgery should be considered if conservative management of congenital chylothorax fails after 4-5 weeks.