Objective: To evaluate whether nasal intermittent mandatory ventilation (NIMV) compared with nasal continuous positive airway pressure (NCPAP) would decrease the requirement for endotracheal ventilation in the treatment of respiratory distress syndrome (RDS) in preterm infants <35 weeks. Study design: Randomized, controlled, prospective, single-center study. Forty-one infants were randomized to NCPAP and 43 comparable infants to NIMV (birth weight 1533 ± 603 vs 1616 ± 494 g, gestational age 30.6 ± 3.0 vs 31.1 ± 2.3 weeks, P = .5, respectively). Results: Infants treated with NIMV and with NCPAP had comparable cardio-respiratory status at study entry. In the total cohort, infants treated initially with NIMV needed less endotracheal ventilation than infants treated with NCPAP (25% vs 49%, P < .05) with a similar trend in infants <1500 g; 31% vs 62%, P =. 06). When controlling for weight and gestational age, NIMV was more successful in preventing endotracheal ventilation (P < .05). Infants treated with NIMV had a decreased incidence of bronchopulmonary dysplasia (BPD) compared with those treated with NCPAP (2% vs 17%, P <. 05, in the total cohort and 5% vs 33%, P <. 05, for infants <1500 g). Conclusions: NIMV compared with NCPAP decreased the requirement for endotracheal ventilation in premature infants with RDS. This was associated with a decreased incidence of BPD.