The current heightened international concern regarding the short and long-term impact of large scale catastrophic events on children and their families has stimulated efforts to develop assessment batteries that can accurately identify youth whose exposure to trauma, loss, and post-event adversities greatly increases their risk for severe, persisting distress, functional impairment and behavioral/developmental disturbance. Measures are needed for a variety of stages of data collection, including those for acute post-impact triage, needs assessment, surveillance, screening, clinical evaluation, intervention outcome and program evaluation. This chapter reviews selected literature on what is known about children's responses and course of recovery after terrorism and war, with a specific focus on assessment domains and metrics for progressive implementation of data collection post-event. The report also presents examples of specific measures that have been constructed and used after a variety of catastrophic events, discusses special issues in regard to the psychometrically, developmentally, psychosocially, and clinically sound assessment of children, the necessity of broadening areas of assessment using multiple informants, cultural competence in designing, adapting and adopting instruments, timing of assessment, and training and supervision issues. Finally, a critical review of available assessment tools is presented, along with recommendations for future research to advance the assessment of children after terrorism and disaster.