The overall goal of this research is to identify factors from the social and physical urban environment, in East Baltimore, and assess their impacts on child activity and anthropometry.  The study aims to: 1) Characterize the spatial distribution of objectively measured environmental variables (social and physical environment, crime, and locations of playgrounds and parks); 2) Establish whether parents’ and children’s perceptions of safety predict children’s activity, defined as: (a) walking to school; (b) amount of time in free play; and (c) use of streets for free play; 3) Explore whether objectively derived measures of the social and physical environment are the same as perceptions of the environment and if not, identify which group of factors is more significant for predicting children’s activity; and 4) Determine if collective efficacy moderates the above noted relationships.