The purpose of this study was to test the reliability and validity of a new instrument for assessing suicidality in adjudicated delinquents. The Suicide Screening Inventory (SSI), a 14-item interview, was evaluated based on archival data from 442 adolescents, primarily male, between the ages of 12 and 20. Two estimates of reliability indicated moderate internal consistency. In addition, a moderate correlation (r= .53) between the SSI and the Reynold's Adolescent Depression Scale suggested convergent validity. Expert ratings of the instrument's utility also provided content validity evidence. Descriptive data were collected on four youth who made suicide attempts. Elevated scores among these select cases provided some evidence for consequential validity. These results are discussed with regard to practical and research implications.