The Healthy Communities Study (HCS) is a 5 year study to investigate how nutrition and physical activity programs and policies in communities across the United States (U.S.) influence children’s weight status and health, and to identify community-related factors that contribute to greater success in promoting health among children. This is the largest study of its kind in the US, with 279 communities and over 23,000 children taking part. The Healthy Communities Study is collecting information from community members on local health programs and policies; from families on their child's health, eating and physical activity behaviors; from health care providers (with parent's/caregiver's approval) on the child's health history; and from local schools and communities on their physical activity and food environments.