OBJECTIVE--To determine what complications children have during interhospital transfer for intensive care, and how often these complications occur. DESIGN--Observational study of all children transferred over a six month period, including interviews with patient escort, patient review, and severity of illness scoring. MAIN OUTCOME MEASURES--Timing and method of transport; complications occurring during transport; the equipment and experience of the escort; patient vital signs and paediatric risk of mortality score on admission; outcome and duration of intensive care. RESULTS--Forty two (75%) of 56 children had adverse clinical events during transport. In 13 the event was life threatening. Inadequate circulatory and ventilatory support, inadequate monitoring, equipment failures, and drug errors were common. Children who subsequently died were more likely to have had complicated transfers than those who survived. CONCLUSIONS--Most children had adverse clinical events during transfer for intensive care. A number are transported by inexperienced staff with inadequate or malfunctioning equipment. Standards for patient management and monitoring during transfer need to be established. To reduce unsatisfactory care during transfer, it is necessary to establish dedicated and specifically trained paediatric transport teams.