Objectives—To examine the relationship between the magnitude, and the relative importance of unintentional child injury mortality with socioeconomic development, and to conceptualise the dynamic changes in injury mortality within the framework of epidemiological transition. Design—Ecological cross sectional study using data on 51 countries. Main outcome measures—The relationship between total mortality rates, unintentional injury mortality rates, and percentage in children 1–14 years of age with gross national product (GNP) per capita. Results—Unintentional injury mortality rates in children were negatively correlated with GNP per capita. However, by categorising the data, we found some areas of non-correlation: in children 5–14 years in low income versus lower middle income countries, and in all age and gender groups in lower high income versus higher high income countries. A high percentage of total deaths due to injuries was clearest in the lower middle income countries in all age and gender groups. Conclusions—The changes in child injury mortality in relation to socioeconomic development could be conceptualised as three stages: a stage of high magnitude; a stage of high priority; and a stage of improvement. Most middle income countries are in the high priority stage where both injury mortality rates and injury percentage of total deaths are high.