Children and adolescents in the U.S. and worldwide are commonly exposed to traumatic events, yet practitioners treating these young people to reduce subsequent psychological harm may not be aware of-or use-interventions based on the best available evidence. This systematic review evaluated interventions commonly used to reduce psychological harm among children and adolescents exposed to traumatic events. Guide to Community Preventive Services (Community Guide) criteria were used to assess study design and execution. Meta-analyses were conducted, stratifying by traumatic exposures. Evaluated interventions were conducted in high-income economies, published up to March 2007. Subjects in studies were <or=21 years of age, exposed to individual/mass, intentional/unintentional, or manmade/natural traumatic events. The seven evaluated interventions were individual cognitive-behavioral therapy, group cognitive behavioral therapy, play therapy, art therapy, psychodynamic therapy, and pharmacologic therapy for symptomatic children and adolescents, and psychological debriefing, regardless of symptoms. The main outcome measures were indices of depressive disorders, anxiety and posttraumatic stress disorder, internalizing and externalizing disorders, and suicidal behavior. Strong evidence (according to Community Guide rules) showed that individual and group cognitive-behavioral therapy can decrease psychological harm among symptomatic children and adolescents exposed to trauma. Evidence was insufficient to determine the effectiveness of play therapy, art therapy, pharmacologic therapy, psychodynamic therapy, or psychological debriefing in reducing psychological harm. Personnel treating children and adolescents exposed to traumatic events should use interventions for which evidence of effectiveness is available, such as individual and group cognitive-behavior therapy. Interventions should be adapted for use in diverse populations and settings. Research should be pursued on the effectiveness of interventions for which evidence is currently insufficient.