The primary aim of the Juega study is to assess the extent to which physical activity, inactivity, and sleep duration are associated with child adiposity in a sample of 100 children entering their first year of school in Ensenada and Tijuana, Mexico. These cities are known for their high rates of drug-related violence, and thus, children may not be as physically active as those in other cities in the country. Energy expenditure and sleep duration have a demonstrated relationship to obesity, but little is known about these behaviors in children in Mexico--especially in young children. Families completed a questionnaire at baseline (before school begins) and follow-up (after completion of the first year of school). During these same time points, we ask children to wear an activity monitor coupled with a Global Positioning System (GPS) unit, to better understand activity levels and the context for that activity. This study began in summer 2012 and is ongoing.