After noting the prevalence of bullying among students from elementary school through high school, the article discusses the various manifestations of bullying as a subtype of aggression. A discussion of the assessment of bullying behavior describes self-report scales, peer and teacher nomination tasks, parent checklists, and behavioral observations. A short section on the bully-victim continuum notes that current research suggests a continuum from victimization to bullying. Further, research has provided a social-ecological perspective of bullying that encompasses individual characteristics as well as environmental and school factors. Individual characteristics include gender; ethnicity/race; developmental phases; and the traits of anger, impulsivity, depression, and suicidal ideation. Environmental and school factors encompass family characteristics, peer relations, and teachers' attitudes. The most effective prevention programs address the ecology of school bullying by using comprehensive approaches that involve students, teachers, administrators, counselors, parents, and community members. School-based programs must be supplemented by individual counseling for some victims and perpetrators. 31 references