This policy brief summarizes the first of many Urban Institute cost-benefit analyses employing an innovative statistical method that enables policymakers to assess the range of possible costs and benefits associated with specific evidence-based programs designed to prevent crime and recidivism. This particular study examined the costs and benefits of the District of Columbia's Community-Based Substance Abuse Treatment (CBSAT) program. The analysis found a 55 percent chance, on average, that the CBSAT program serving 150 people will yield benefits exceeding its costs.