OBJECTIVE: To calculate the preventable fraction of unintentional childhood injury deaths in the United States. DESIGN: Ecological study of cause specific unintentional childhood injury mortality rates across the 50 states (and the District of Columbia) of the United States (US) over the 10 year period 1989-98. METHODS: The internet accessible database from the National Center for Injury Prevention and Control was used in order to estimate unintentional childhood (0-14 years) injury mortality rates by external cause and time trends over the study period for each of the US states and for the four major geographical regions of the country. In the principal analysis, a calculation was made of the fraction and absolute number of unintentional childhood injury deaths that could have been prevented annually if the mortality rate in the region with the lowest rate also existed in the remaining three. In another scenario, the lowest external cause specific unintentional childhood injury mortality rates from the 50 US states and the District of Columbia were summed to provide the "ideal" lowest conceivable unintentional childhood injury mortality rate from all causes. Ecological correlations between unintentional childhood injury mortality rates from specified external causes, median income, and percent of the population with a college degree were made. MAIN OUTCOME MEASURES: Unintentional childhood injury mortality rates by cause. RESULTS: Unintentional childhood injury mortality rate declined by 3.5% per year in the country as a whole. If every region of the US had experienced the same injury rate as the Northeast, then one third of all unintentional childhood injuries would not have occurred. More optimistic scenarios indicate that up to two thirds of all unintentional childhood injury deaths could be prevented. Across states, unintentional childhood injury mortality is strongly inversely related to median income. CONCLUSIONS: About one third of all unintentional childhood injury deaths in the US are preventable with the means and resources available in the Northeastern states. Among the relevant characteristics in the Northeast region, in comparison with other US regions, are the higher education level of parents, the lower gun ownership, the higher population density that implies shorter distances traveled by cars, a better developed emergency medical system, and the existence of several injury prevention programs.