Priority health-risk behaviors (i.e., interrelated and preventable behaviors that contribute to the leading causes of morbidity and mortality among youths and adults) often are established during childhood and adolescence and extend into adulthood. The Youth Risk Behavior Surveillance System (YRBSS), established in 1991, monitors six categories of priority health-risk behaviors among youths and young adults: 1) behaviors that contribute to unintentional injuries and violence; 2) sexual behaviors that contribute to human immunodeficiency virus (HIV) infection, other sexually transmitted diseases, and unintended pregnancy; 3) tobacco use; 4) alcohol and other drug use; 5) unhealthy dietary behaviors; and 6) physical inactivity. In addition, YRBSS monitors the prevalence of obesity and asthma among this population.