Data on childhood obesity collected by the Centers for Disease Control and Prevention helped reveal the nation's epidemic of overweight and obese children. But more information is needed. Collecting body mass index (BMI)-the widely accepted measurement of childhood weight status-at the state and local levels can be instrumental in identifying and tracking obesity trends, designing interventions to help overweight children, and guiding broader policy solutions. Approximately thirty states have enacted or proposed BMI surveillance laws and regulations. Arkansas stands out as the state with the highest-quality surveillance data. Innovative strategies being pursued in a number of other states should be explored for broader dissemination.