Study objective: To study municipal variations in children's injury risk and to assess the impact of safety promotion measures in general municipal, preschool, school, and leisure activity settings, on injury outcome.Design: A cohort study based on individual data on children's consumption of hospital care as a result of injury, the age and sex of each child, and socioeconomic data on each child's mother. Municipal characteristics-that is, population density and municipal safety measures-were also used. Connections between individual and community level determinants were analysed with multilevel logistic regression.Setting: Twenty five municipalities in Stockholm County in Sweden were studied.Participants: Children between 1 and 15 years old in 25 municipalities in Stockholm County, identified in the Total Population Register in Sweden. The study base included 1 055 179 person years.Main results: Municipality injury rates varied between 3.84-7.69 per 1000 person years among 1-6 year olds and, between 0.86-6.18 among 7-15 year olds. Implementation of multiple safety measures in a municipality had a significant effect on the risk of injury for preschool children. In municipalities that implemented few safety measures, the risk of injury was 33% higher than in municipalities that implemented many. A similar effect, though insignificant, was observed in the school aged children.Conclusions: This study shows that how municipalities organise their safety activities affect injury rates. Sweden has a comparatively low injury rate and thus, in a European perspective, there is an obvious potential for municipal safety efforts.