Efforts to address the major health, environmental, and social threats that can be found across the globe rely on changes in human behavior. Yet identifying effective and efficient ways to change behavior remains a vexing challenge. To meet this need, investigators need to design and evaluate behavioral intervention strategies in a manner that affords the creation of evidence-based guidelines that specify not only whether interventions work but also how and under what conditions. In this chapter, the design and testing of interventions are situated within the experimental medicine approach. This approach leverages the strength of the experimental method to test how behavior change intervention strategies work and to identify the conditions under which they operate effectively. Moreover, it organizes how investigators specify the questions that underlie the study of behavior change interventions and requires them to articulate precisely what intervention strategy they are using, how they think the strategy operates, and the outcomes it generates. Through the systematic use of this approach, evidence will emerge that addresses practitioners’ prevailing concerns directly – what intervention strategy is the most effective and efficient way to address the problem at hand. This chapter provides an overview of how to implement the experimental medicine approach, describes its key features, and addresses the importance of precision and, finally, considers this approach within a broader set of initiatives that have emerged to support a programmatic approach to the design, evaluation, and implementation of behavior change interventions.