When sick newborn babies are transferred to Hammersmith Hospital they are collected from the referring hospital or from home by a paediatric resident doctor and a nurse. They prepare the baby for the journey by giving any urgent treatment required, for procedures are difficult to carry out in a moving ambulance. Babies who are likely to become apnoeic are intubated before transport so that ventilation can be started immediately if required. The baby travels in a portable incubator, and special attention is paid to prevention of hypothermia, adequate oxygenation, and respiration. Altogether 122 babies were transferred in 1969, the main reasons being prematurity, hyaline membrane disease, and apnoeic attacks. Five improved during the journey, 102 did not change significantly and 15 became worse. There was no evidence that travel per se harmed any of the babies, though in a few cases deterioration might have been prevented had observation and treatment been easier in the ambulance. Fifty-eight (47%) of the babies eventually died, but the group was a highly selected one with a high proportion of small, immature, and ill babies. We conclude that for very ill newborn babies the advantages of transfer to an intensive care unit probably outweigh the disadvantages of transport, provided that the precautions described here are taken.