Accident occurrence and measures of physical activity, total development and conduct difficulties were recorded for 9391 pre-school children recruited to the Avon Longitudinal Study of Parents and Children (ALSPAC) study in southwest England. Information about their mothers' age at delivery, post-natal depression, life events, social support and smoking status was also included. Multilevel modelling was used to identify variations between alternative sets of subjective and automated zone design neighbourhoods, which incorporated different boundaries and different scales. The risk of accidents to pre-school children, and most of the characteristics of children and mothers associated with accident risk, varied significantly between neighbourhoods. Differences in the strength of area effects between alternative sets of neighbourhoods were small, although slightly stronger effects were observed in areas with populations less than 4000. Neighbourhoods subjectively defined by planners did not produce stronger effects than computer-generated areas.