The article lays a foundation for developing an effective assessment approach to evaluate the risk of targeted violence in schools by addressing four issues. First, the authors delineate the contours of the problem of targeted violence by distinguishing the fear of this violence from its actual probability and by distinguishing targeted violence from other forms of aggression by youth. Second, they examine and critique three assessment approaches -- profiling, guided professional judgment, and automated decision making -- that have been advocated and used in some schools to identify students at risk for violence, giving particular consideration to the potential for harm inherent in these current approaches. Finally, the authors describe and explore the utility of a threat assessment approach intended to identify and assess the risk posed by a potential student perpetrator as regards targeted violence in school. The authors argue that the most effective approach for understanding and preventing planned school-based attacks is informed by empirically derived knowledge about the antecedents, motives, idea development, communications, and planning behavior of all known perpetrators of targeted school violence. 80 references