Youth Risk Behavior Survey
The Youth Risk Behavior Survey (YRBS) is an American biennial survey of adolescent health risk and health protective behaviors such as smoking, drinking, drug use, diet, and physical activity conducted by the Centers for Disease Control and Prevention. It is one of the major sources of information about these risk behaviors, and is used by federal agencies to track drug use, sexual behavior, and other risk behaviors.
The YRBS was created in the early 1990s in order to monitor progress towards protecting youth from HIV infection. There are only two repeated nationally-representative surveys which give all the information in existence about youth risk behavior; YRBS and the University of Michigan's Monitoring the Future (MTF). Every academic research study which evaluates national US trends over time in adolescent smoking, drinking, drug use, sexual activity, or other health behaviors is based on these two studies. There are no other nationally-representative sources of information about these behaviors other than YRBS and MTF. (Edit: There's also the National Longitudinal Study of Adolescent to Adult Health, which is nationally representative and covers all these topics.)
The YRBS is the official source of information about adolescent risk behaviors used to evaluate federal, state, and local public health initiatives to decrease these risk behaviors.