The three main sources of information about trends in youth violence include police statistics, youth surveys, and the National Crime Victimization Survey. Self-reported violent behavior has been relatively stable during the past two decades, but the number of youths who carry weapons and display aggressive behaviors remains high. Survey data reveal that youth are often victims of violence. Adolescents between ages 12 and 19 were 2 times more likely than adults ages 25-34 and 3 times more likely than adults ages 35-49 to be victims of murder, aggravated assault, forcible rape, sexual assault, and robbery in 1997. Racial, ethnic, and gender differences in the prevalence of youth violence have occurred for much of the past century. Youth violence takes many forms. Parents, teachers, peers, or neighbors often do not perceive perpetrators as dangerous. This factor makes prediction and prevention of violence behavior challenging. Subsequent chapters in this volume discuss etiological factors and strategies to assess propensity toward and involvement in violent behavior, innovative prevention and treatment strategies, and policy recommendations to address structural factors related to the onset and maintenance of youth violence. Figures, table, and 49 references