For many years, notes Alex Piquero, youth of color have been overrepresented at every stage of the U.S. juvenile justice system. As with racial disparities in a wide variety of social indicators, the causes of these disparities are not immediately apparent. Some analysts attribute the disparities to "differential involvement" - that is, to differences in offending by minorities and whites. Others attribute them to "differential selection" - that is, to the fact that the justice system treats minority and white offenders in different ways. Still others believe the explanation lies in a combination of the two. Differential involvement may be important earlier in the judicial process, especially in youths' contacts with police, and may influence differential selection later as individuals make their way through the juvenile justice system. Adjudicating between these options, says Piquero, is difficult and may even be impossible. Asking how much minority overrepresentation is due to differences in offending and how much to differences in processing no longer seems a helpful way to frame the discussion. Piquero urges future research to move beyond the debate over "which one matters more" and seek to understand how each of the two hypotheses can explain both the fact of minority overrepresentation in the juvenile justice system and how best to address it. Piquero cites many sizable gaps in the research and policy-relevant literature. Work is needed especially, he says, in analyzing the first stage of the justice system that juveniles confront: police contacts. The police are a critical part of the juvenile justice decision-making system and are afforded far more discretion than any other formal agent of social control, but researchers have paid surprisingly little attention to contacts between police and citizens, especially juveniles. Piquero notes that some states and localities are undertaking initiatives to reduce racial and ethnic disparities. He urges researchers and policymakers to evaluate such initiatives, especially those using strategies with a track record of success. Researchers should also examine empirically the far-reaching consequences of disproportionate minority representation in the juvenile justice system, such as poor outcomes in education, labor force participation, and family formation. Finally, Piquero emphasizes that one critical research area involves updating justice system data systems and repositories, which have failed to track changes in U.S. demographic and immigration patterns.