1. To determine, in preterm infants who have received an initial dose of surfactant either as prophylaxis or treatment of established respiratory distress syndrome, whether the use of a high threshold for administration of a second or subsequent dose of surfactant when compared to a low threshold leads to improved respiratory outcome, decreased morbidity associated with prematurity, decreased resource utilization and decreased mortality.

2. To compare the effects of high versus low thresholds in different subgroups formed on initial dosing strategy (prophylactic dosing versus rescue dosing), degree of prematurity, birth weight, type of ventilator (conventional versus HFOV), antenatal steroid use, and the type of surfactant (natural versus synthetic)