A retrospective study of all neonates with birthweight 2000 g or less undergoing major cardiac surgery at the Royal Children's Hospital, Melbourne over the last 5 years was performed in order to determine outcome and identify subgroups within this population that may have a poor prognosis. The mean length of stay in intensive care following surgery was 32 days, with non-survivors having a significantly longer duration of stay than survivors. Overall mortality was 43%, and for children with congenital heart disease as part of a recognizable syndrome the mortality was 100%. None of the survivors suffered incapacitating cardiac, neurological or respiratory handicap. These children in general have a poor prognosis and utilize significant resources; results of cardiac surgery in this group need to be closely followed in the future.