To develop a brief screening tool that will allow emergency department (ED) staff to rapidly and accurately detect suicide risk in child and adolescent patients. Cross-sectional survey. Participants. One hundred forty-four children and adolescents, mean age of 13.6 years, presenting to an urban university teaching hospital pediatric ED for primarily psychiatric reasons. Data Collection. As part of a quality improvement initiative, we developed a 14-item screening survey (the Risk of Suicide Questionnaire [RSQ]) that was administered by a triage nurse to all pediatric mental health patients on admission to the ED. All patients were subsequently administered the 30-item Suicide Ideation Questionnaire (SIQ) by a mental health clinician, which served as the criterion standard assessment of suicidality. Other information collected included demographic and clinical characteristics. Sensitivity, specificity, positive predictive value, negative predictive value (NPV), and area under the receiver operating characteristic curve for responses to individual and combinations of RSQ items, relative to determinations of suicidality by the criterion standard SIQ. Four of the items from the RSQ had a predictive c statistic of 0.87, a sensitivity of 0.98, and a NPV of 0.97. Little improvement in predictive ability was obtained by including other RSQ items (c statistic for the most predictive 4-item model = 0.87; c statistic for the model containing all 14 items = 0.90). Among all possible combinations of 4 RSQ items, the combination of items inquiring about current suicidal behavior, past suicidal ideation, past self-destructive behavior, and current stressors yielded the highest sensitivity (0.98), NPV (0.97), and c statistic (0.87), as assessed by the criterion standard SIQ. A brief 4-item screening tool can be used by nonmental health clinicians to accurately detect suicidality in children and adolescents who visit an ED. Early and accurate identification of suicidality is a critical first step that could lead to better treatment and improved health outcomes for children and adolescents with mental health concerns.