Few prospective studies of mortality among children in developing countries have been published. Here we quantify and describe mortality and injury morbidity among a cohort of schoolchildren in rural Southeast Asia. Deaths among a cohort of 40,119 schoolchildren in Thailand were prospectively monitored over a two year period from January 1991. Additionally, data were collected with a questionnaire from a subset of 6,378 children asking them to recall all injuries over a one-year period. There were 40 deaths for an annual incidence of 50/100,000. Fifty percent of all deaths were due to injury; 25% to infectious diseases. Sixty percent of the injury deaths were due to motor vehicles and 35% to drowning. Sixty-six percent of the children reported one or more accidents. The leading categories of non-fatal injuries, in decreasing order, were: animal bite, puncture wound, burn, near-drowning, fall from a height. Boys experienced more injuries than girls for almost every type of injury. Injuries are replacing infectious diseases as the most important cause of deaths in developing countries. Additional public health initiatives to reduce childhood accidents may be warranted.