The emergence of theory-driven evaluation has drawn attention to the need for practical ways for evaluators to construct program theory to achieve the benefits of the approach. This article illustrates the use of concept mapping as a technique to explicate underlying program theory in the context of family support programs. In this example, 29 professional staff members from a statewide family support program brainstormed 96 specific benefits for participant families. Fourteen direct service staff members sorted and rated the items and interpreted the map produced by multidimensional scaling analysis and hierarchical cluster analysis. Some of the benefits of the technique for evaluators conducting theory-driven evaluations are highlighted. These include helping evaluators decide what to measure, capturing the complexity of programs in the context of implementation, and managing good stakeholder-evaluator relations. The general limitations and issues of concept mapping as it applies to theory development are also discussed.