In the newborn infant, accurate endotracheal tube (ETT) placement is essential for adequate ventilation and surfactant delivery. This study aimed to determine the relationship between gestation, weight and endotracheal tube length, and to evaluate the promotion of gestation-based guidelines for ETT length. A prospective audit of endotracheal tube placement, followed by an education drive to 24 hospitals, and a subsequent repeat audit. Neonatal intensive care transfer service. Infants referred for inter-hospital transfer between 33 neonatal units. Education drive to local hospitals to encourage use of standardised guidelines for ETT length based on gestation. Endotracheal tube length, radiological position with respect to thoracic vertebral bodies and radiological complications were assessed by neonatal transport team staff. The association between satisfactory ETT length and gestation was linear, whereas the relationship with weight was non-linear. In participating centres, use of gestation-based guidelines were associated with a reduction in tubes needing repositioning (8% vs. 53%, p<0.01) and in the incidence of uneven lung expansion (3% vs.17%, p<0.05). As use of gestation guidelines increased from 18% to only 32% overall, the intervention did not produce statistically significant changes in the entire patient population. Use of gestation-based guidelines on ETT length for neonatal intubation was associated with a reduction in tube malposition and uneven lung expansion. A table of ETT length against gestation and weight is provided to assist those carrying out this procedure, which could be incorporated into neonatal resuscitation training.