Among 1 186 neonates admitted consecutively to the Post-Royal intensive care Unit, 203 had respiratory distress, a chest roentgenogram typical of delayed resorption of lung fluid, and no other findings. Mean gestational age (GA) was 33 weeks and mean birth-weight (BW) was 1 948 g. Hood oxygen alone was used in 129 cases and intubation-ventilation-PEEP in 74 cases (46 of which were intubated before admission). The occurrence of radiological features was similar in ventilated and non-ventilated neonates : ground-glass pattern (70-80% of the cases), increased vascular markings (70-76%) enlarged right fissure (45%), thin lateral pleural density (24%) and normal cardio-thoracic ratio. The analysis of other prognostic factors showed that ventilated neonates had a significantly lower birth weight (1 689 g versus 2 097 g) and a significantly younger gestational age (31.9 versus 33.6). The study of DAa02 in non-ventilated neonates demonstrated wide individual variations, and the possibility of an early normal DAa02 but also of a late abnormal DAa02, with the associated risks of early hyperoxia or prolonged oxygen needs. In ventilated neonates, the mean duration of intubation was 4 days 13 hours; this duration decreased as the birth-weight rose. In view of the major role of BW and GA, the Port-Royal team advocates the direct admission to a neonatal intensive care unit of neonates with delayed resorption of lung fluid and a BW under 2 000 g. In this way, Pa02 can be closely monitored and artificial ventilation is readily available.