The *MMWR* series of publications is published by the Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services, Atlanta, GA 30329-4027. This report summarizes the results of the 2017 Youth Risk Behavior Surveillance System (YRBSS) survey, which monitors six categories of priority health-related behaviors among youth and young adults in the United States: unintentional injuries and violence, tobacco use, alcohol and other drug use, sexual behaviors related to unintended pregnancy and sexually transmitted infections (STIs), unhealthy dietary behaviors, and physical inactivity. The report also includes data on obesity, overweight, and asthma. The 2017 YRBSS survey covered 121 health-related behaviors and provided updates on the prevalence of these behaviors by demographic subgroups defined by sex, race/ethnicity, grade in school, and sexual minority status. The survey found that many high school students engage in health-risk behaviors, such as texting or emailing while driving, current alcohol and marijuana use, and taking prescription pain medication without a doctor's prescription. Additionally, the survey revealed high rates of bullying, suicide attempts, and sexual risk behaviors, including sexual intercourse and multiple sexual partners. Many students also reported unhealthy behaviors related to chronic diseases, such as smoking cigarettes and using electronic vapor products. The report highlights significant health disparities among demographic subgroups, particularly between sexual minority and nonsexual minority youth. Sexual minority students reported higher prevalence rates for many health-risk behaviors compared to nonsexual minority students. However, long-term temporal trends indicate that the overall prevalence of most health-risk behaviors has moved in a positive direction. The YRBSS data are used to monitor the effectiveness of public health interventions and to inform policy and practice to reduce health-risk behaviors and improve health outcomes among youth. The report emphasizes the importance of addressing these behaviors to ensure the health and well-being of young people.The *MMWR* series of publications is published by the Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services, Atlanta, GA 30329-4027. This report summarizes the results of the 2017 Youth Risk Behavior Surveillance System (YRBSS) survey, which monitors six categories of priority health-related behaviors among youth and young adults in the United States: unintentional injuries and violence, tobacco use, alcohol and other drug use, sexual behaviors related to unintended pregnancy and sexually transmitted infections (STIs), unhealthy dietary behaviors, and physical inactivity. The report also includes data on obesity, overweight, and asthma. The 2017 YRBSS survey covered 121 health-related behaviors and provided updates on the prevalence of these behaviors by demographic subgroups defined by sex, race/ethnicity, grade in school, and sexual minority status. The survey found that many high school students engage in health-risk behaviors, such as texting or emailing while driving, current alcohol and marijuana use, and taking prescription pain medication without a doctor's prescription. Additionally, the survey revealed high rates of bullying, suicide attempts, and sexual risk behaviors, including sexual intercourse and multiple sexual partners. Many students also reported unhealthy behaviors related to chronic diseases, such as smoking cigarettes and using electronic vapor products. The report highlights significant health disparities among demographic subgroups, particularly between sexual minority and nonsexual minority youth. Sexual minority students reported higher prevalence rates for many health-risk behaviors compared to nonsexual minority students. However, long-term temporal trends indicate that the overall prevalence of most health-risk behaviors has moved in a positive direction. The YRBSS data are used to monitor the effectiveness of public health interventions and to inform policy and practice to reduce health-risk behaviors and improve health outcomes among youth. The report emphasizes the importance of addressing these behaviors to ensure the health and well-being of young people.