This study examined the validity, reliability, equity, and cost of nine juvenile justice risk assessment instruments. Though many researchers and practitioners believe that risk assessment is critical to improving decision making in the juvenile justice system, the range of options currently available makes the selection of the most appropriate instrument for each jurisdiction a difficult choice. This study was designed to provide a comprehensive examination of how several risk assessments perform in practice (p. 1). Findings are reported: according to eight risk assessment instruments; and through a comparison of results across jurisdictions and assessments by way of reliability, validity, equity, revised risk assessment instruments constructed in the study, and efficiency and cost. A discussion covers: instruments developed for general use; risk instruments developed for a specific agency; and comments from Advisory Board members and responses from the authors of this report. Risk assessment should be a simple process that can be easily understood and articulated. This study’s findings show that simple, actuarial approaches to risk assessment can produce the strongest results. Adding factors with relatively weak statistical relationships to recidivism—including dynamic factors and criminogenic needs—can result in reduced capacity to accurately identify high-, moderate-, and low-risk offenders (p. vi).