This cost-benefit analysis of implementing a Functional Family Therapy (FFT) program in the District of Columbia indicates that the benefits are likely to outweigh the costs. The analysis employed 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. Results indicate that there is a 66 percent chance that an FFT program serving 150 juveniles will yield benefits exceeding its costs.