We aimed to compare the strategy of non-selective neuromuscular paralysis with that of synchronised (fast rate) ventilation and selective paralysis in infants receiving mechanical ventilation for RDS with chronic lung disease as the primary outcome measure. One hundred and ninety-three infants under 24 hours of age were enrolled in the study and were allocated to receive either pancuronium during mechanical ventilation in the acute phase of RDS (non-selective group) or synchronised ventilation (initial ventilatory rate at or above that of the infant's) (selective group). Infants in the selective group received pancuronium if they were consistently expiring during the inspiratory phase of the ventilator. There was no significant difference between the groups with respect to birth weight, gestation and sex distribution. There was no significant difference between the groups with respect to death (selective 19%; non-selective 16%). pneumothorax (selective 13 %: nonselective 16%, CLD (selective 47%, non-selective 47%) and oxygen, dependency at 36 weeks post conceptual age (selective 27%: non-selective 34% Routine paralysis of ventilated infants has potential complications which may be avoided by using synchronised ventilation. As the latter is not associated with an increased incidence of long term respiratory complications we conclude that it is the optimal strategy of the two for ventilating infants with RDS.