In order to avoid endotracheal intubation in very small newborn infants requiring prolonged intermittent positive pressure ventilation (IPPV), a method was developed allowing delivery of IPPV by means of nasal prongs (nasal IPPV). A series of 10 newborn infants weighing 1 200 g or less, and requiring nasal IPPV for 5 to 14 days because of intractable apnea has been reported. Five infants survived. With the exception of hearing defects in two survivors, no lesions possibly due to the ventilation procedure were observed. Follow-up examination showed severe mental and motor handicap in one infant, and apparently normal mental and motor development in 3 infants examined at the age of 12-27 months. It is suggested that nasal IPPV is an effective and safe method for prolonged ventilation of very small newborn infants with normal or not severely affected lungs, whereas it appears of very limited use in patients with stiff lungs, such as in severe HMD.