Discussing data collected by the Youth Risk Behavior Surveillance System (YRBSS) from February 2001 to December 2001, this weekly mortality and morbidity report addresses priority health-risk behaviors among youths and adolescents that contribute to unintentional injuries and violence. After discussing the ways that motor-vehicle crashes, unintentional injuries, homicide, suicide, pregnancies, and sexually transmitted diseases (STDs) account for the vast majority of deaths among youths and young adults, this report presents the methodology used by the 2001 national school-based YRBSS in obtaining 13,601 usable questionnaires concerning health-risk behaviors. The data collection resulted in categories of behaviors that lead to health risks in adolescents and young adults. A lack of seat belt, motorcycle helmet, or bicycle helmet use; riding with a driver who had used alcohol; or driving after drinking alcohol were behaviors classified as contributing to “Unintentional Injuries.” Carrying a weapon, fighting, sexual and school violence, and suicide attempts were behaviors classified as “Violence.” Cigarette, cigar, and smokeless tobacco use were classified as both “Tobacco Use” and “Age of Initiation of Risk Behaviors,” while use of alcohol, marijuana, cocaine, inhalants, heroine, methamphetamine, steroids, and injection drugs were classified as “Alcohol and Other Drug Use” behaviors. A lack of condom or birth control pill use, using alcohol or drugs at the time of sexual intercourse, pregnancy, and a lack of HIV education were behaviors categorized as health-risk “Sexual Behaviors.” Health-risk “Dietary Behaviors” included being overweight, a lack of fruit, vegetable, or milk consumption, and engaging in excessive weight control, while health-risk “physical activity” behaviors included a lack of physical activity, a lack of physical education classes, a lack of participating in team sports or strengthening exercises, and excessive television watching. Forty-six tables and graphs illustrating the statistics within each of these categories are located at the end of this report.