Continuous positive airway pressure (CPAP) was employed using nasal prongs in 30 neonates with hyaline membrane disease (HMD). There was a significant improvement in mean PaO2 (from 47 to 80 mmHg;p less than 0.001) with no significant change in PaCO2 or pH within a mean 36 min of therapy. Use of the technique allowed reduction of FiO2 to less than 0.60 in less than 20 h in 18 infants. Infants treated within 24 h of birth had significantly greater improvements in PaO2. Complications were infrequent and only 3 of 30 babies developed a pneumothorax while on nasal CPAP. Only 1 of the 23 survivors required mechanical ventilation in addition to nasal CPAP.