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 Pa02 (from 47 to 80 mmHg; p < 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 < 0.60 in < 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.