The Youth Risk Behavior Surveillance System (YRBSS) is an epidemiologic surveillance system that was established by the Centers for Disease Control and Prevention (CDC) to monitor the prevalence of youth behaviors that most influence health. The 2011 national school-based Youth Risk Behavior Survey (YRBS) is one component of the YRBSS. The YRBS focuses on priority health-risk behaviors established during youth that result in the most significant mortality, morbidity, disability, and social problems during both youth and adulthood. These include: behaviors that result in unintentional and intentional injuries; tobacco use; alcohol and other drug use; sexual behaviors that result in HIV infection, other sexually transmitted diseases (STDs), and unintended pregnancies; dietary behaviors; and physical activity, plus overweight and asthma. The results from the YRBS will be used by CDC to (1) monitor how priority health-risk behaviors among high school students (grades 9-12) increase, decrease, or remain the same over time; (2) evaluate the impact of broad national, state, and local efforts to prevent priority health-risk behaviors; and (3) monitor progress in achieving three leading health indicators and 15 Healthy People 2010 national health objectives. Results also will be used to help focus programs and policies for comprehensive school health education on the behaviors that contribute most to the leading causes of mortality and morbidity. For more information on the Youth Risk Behavior Surveillance System (YRBSS), visit the Centers for Disease Control and Prevention web site at http://www.cdc.gov.