Bicycle injuries are an important cause of trauma. Approximately 75% of such accidents occur in children and involve difficult decisions in the areas of education, engineering and legislation. A prospective 3-year study was undertaken to understand the range of injuries and in particular to concentrate on severe injuries. In all, 251 children were admitted to Westmead Hospital after receiving bicycle injuries. Most injuries were minor but there were 37 serious injuries and six deaths. Head injuries predominated, especially in the seriously injured. The rate of wearing helmets was low, with less than 10% of all admissions wearing a helmet. None of the seriously or fatally injured wore a helmet. Helmet-wearing remains the single most important preventative measure to be instituted if the serious morbidity and mortality rates associated with bicycle injuries are to decrease.