IMPORTANCE Although immature neonate survival has improved, there is an increased risk of developing bronchopulmonary dysplasia, leading to significant respiratory morbidity. Measures to reduce bronchopulmonary dysplasia are not always effective or have important adverse effects. OBJECTIVE To evaluate the effect of late surfactant administration in infants with prolonged respiratory distress on ventilation duration, respiratory outcome at 36 weeks' postmenstrual age, and at 1 year postnatal age. DESIGN, SETTING, AND PARTICIPANTS Double-blind randomized clinical trial at 13 level III French perinatal centers. Participants included 118 neonates at less than 33 weeks' gestation who still required mechanical ventilation on day 14 (SD, 2) with fraction of inspired oxygen of more than 0.30. All survivors were eligible for follow-up. We performed an intent-to-treat analysis. INTERVENTIONS Infants received 200 mg/kg of poractant alfa (surfactant) or air after randomization. At 1 year, after parents' interview, infants underwent physical examination by pediatricians not aware of the randomization. MAIN OUTCOMES AND MEASURES The duration of ventilation was the primary outcome. The combined outcome of death or bronchopulmonary dysplasia at 36 weeks' postmenstrual age and respiratory morbidity at 1 year of age were the main secondary outcome measures. RESULTS Of the 118 infants who participated in the study, 65 (55%) were male. Fraction of inspired oxygen requirements dropped after surfactant, but not air, for up to 24 hours after instillation (0.36 [0.11] vs 0.43 [0.18]; P < .005). Severe bronchopulmonary dysplasia/death rates at 36 weeks' postmenstrual age were similar (27.1% vs 35.6%; P = .32). Less surfactant-treated infants needed rehospitalization for respiratory problems after discharge (28.3% vs 51.1%; P = .03); 39.5% vs 50% needed respiratory physical therapy (P = .35). No difference was observed for weight (7.8 [1.2] kg vs 7.6 [1.1] kg), height (69 [5] cm vs 69 [3] cm), and head circumference (44.4 [1.7] cm vs 44.2 [1.7] cm) measured at follow-up, nor for neurodevelopment outcome. CONCLUSIONS AND RELEVANCE Late surfactant administration did not alter the early course of bronchopulmonary dysplasia. However, surfactant-treated infants had reduced respiratory morbidity prior to 1 year of age.