This chartbook investigates areas where U.S. adolescents' health or health-related behaviors emerged as significantly different from those of adolescents in other counties in positive, negative, or suggestive directions. Data come from the international Health Behavior in School-aged Children (HBSC) study, which has coordinated comparable, nationally representative school-based surveys of teens every 4 years since 1985-86. The HBSC study examines adolescent health and health-related behavior in the context of family, school, and peers, using international comparisons to demonstrate common factors and highlight differences associated with cultural influences. This report provides data on teens age 15 years old, although the study addresses teens age 11, 13, and 15 years. Results are presented on: (1) "Health and Well-Being"; (2) "Fitness"; (3) "Family and Peer Relationships"; (4) "School Environment"; (5) "Smoking and Alcohol Use"; and (6) "Violence." Overall, U.S. youth are more likely to have stomachaches, headaches, backaches, and difficulty sleeping than students in most other countries, possibly related to fitness levels. U.S. students find it easy to make new friends but are among the least likely to consider students in their classrooms kind and helpful. U.S. youth are less likely to smoke than students in most countries. They rank relatively high for never or rarely feeling safe at school. (Chapters contain references.) (SM)