Many treatment programs have adopted or are considering adopting evidence-based treatments (EBTs). When a program evaluates whether to adopt a new intervention, it must consider program objectives, operational goals, and costs. This article examines cost concepts, cost estimation, and use of cost information to make the final decision on whether to adopt an EBT. Cost categories, including variable and fixed, accounting and opportunity, and costs borne by patients and others, are defined and illustrated using the example of expenditures for contingency management. Ultimately, cost is one consideration in the overall determination of whether implementing an EBT is the best use of a program's resources.