Achievement testing is the centerpiece of the state accountability systems mandated by the federal No Child Left Behind Act (NCLB). The public attention directed toward achievement scores, however, has largely eclipsed the crucial role that graduation rates play in NCLB accountability. As a result, we are only now beginning to appreciate the complexities of several key issues. Those include the origins of the law's concern about graduation rates, the status of graduates and dropouts for NCLB accountability, the consequences of using different ways to define and measure graduation rates, and state strategies for incorporating graduation rates into their federal accountability plans. Drawing on recent research at the Urban Institute, this brief clarifies these issues and offers a foundation of knowledge upon which to ground ongoing discussions and analyses of the law.