We reviewed the coroner's records of all fatal bicycle accidents occurring in children (aged 0 to 15 years) in Ontario (pediatric population, 2,007,230) between January 1, 1985 and December 31, 1989. The injuries sustained were documented and scored with anatomical injury scores (Abbreviated Injury Score 1985 and Injury Severity Score) and categorized as unsurvivable or survivable. The causes and circumstances were documented from police accident reports. Eighty-one deaths resulted from bicycle accidents, an annual mortality rate of 1.44 deaths per 100,000 children per year. In 74 (91%) of these cases the injuries were deemed unsurvivable, 89% of which were head injuries. Seventy-eight (96%) of the deaths resulted from collisions with motor vehicles. No victim was wearing a helmet at the time of injury. In 70% of the deaths, the cyclist was considered to have caused the collision, either because of a violation of a road traffic law or poor road sense. These findings suggest that more emphasis should be placed on primary and secondary injury prevention by such methods as bicycle safety education for children and the promotion of bike helmet use. In addition, in view of the high incidence of unsurvivable head injury, the introduction of legislation requiring the use of protective helmets should be considered.