Objectives: To examine trends in child mortality from unintentional injury between 1985 and 1992 and to find how changes in modes of travel contributed to these trends. Design: Poisson regression modelling using data from death certificates, censuses, and national travel surveys. Setting: England and Wales. Subjects: Resident children aged 0-14. Main outcome measures: Deaths from unintentional injury and poisoning. Results: Child deaths from injury declined by 34% (95% confidence interval 28% to 40%) per 100 000 population between 1985 and 1992. Substantial decreases in each of the leading causes of death from injury contributed to this overall decline. On average, children walked and cycled less distance and travelled substantially more miles by car in 1992 compared with 1985. Deaths from road traffic accidents declined for pedestrians by 24% per mile walked and for cyclists by 20% per mile cycled, substantially less than the declines per 100 000 population of 37% and 38% respectively. In contrast, deaths of occupants of motor vehicles declined by 42% per mile travelled by car compared with a 21% decline per 100 000 population. Conclusions: If trends in child mortality from injury continue the government's target to reduce the rate by 33% by the year 2005 will be achieved. a substantial proportion of the decline in pedestrian traffic and pedal cycling deaths, however, seems to have been achieved at the expense of children's walking and cycling activities. changes in travel patterns may exact a considerable price in terms of future health problems. Injuries are the leading cause of death in children over 1 year old, and we assessed the extent to which trends in mortality from transport related injury reflected changes in children's travel patterns Child mortality from accidental injury declined by 34% between 1985 and 1992, while children walked and cycled less distance and travelled substantially more by car in 1992 compared with 1985 Substantial decreases in deaths from road traffic accidents for pedestrians and cyclists were at the expense of walking and cycling activities Car travel became safer for children, but the effect on mortality was largely nullified by large increases in the distances children travel by car Although these changes are in accordance with government targets to reduce child mortality from accidental injury, the associated decline in children's physical activity may lead to future health problems