In this chapter, we consider strategies for producing behavior change on a large scale, analyzing various intervention efforts in light of their capacity to move people toward desirable behavior and away from undesirable behavior. Invariably, these efforts aim to restructure material and psychological incentives, often in very clever ways. However, as we will argue, their success depends ultimately on two rather subtle and often overlooked factors: (1) the motivational structure of the status quo before the intervention is undertaken, and (2) the complex and nonadditive relationship between material and psychological incentives. We will begin with a brief overview of how psychologists have traditionally approached the task of changing behavior, which provides the conceptual grounding for our subsequent analysis. In this chapter, we consider strategies for producing behavior change on a large scale, analyzing various intervention efforts in light of their capacity to move people toward desirable behavior and away from undesirable behavior. Invariably, these efforts aim to restructure material and psychological incentives, often in very clever ways. However, as we will argue, their success depends ultimately on two rather subtle and often overlooked factors: (1) the motivational structure of the status quo before the intervention is undertaken, and (2) the complex and nonadditive relationship between material and psychological incentives. We will begin with a brief overview of how psychologists have traditionally approached the task of changing behavior, which provides the conceptual grounding for our subsequent analysis.