This chapter reviews some of the medication adherence interventions, with a special focus on reinforcement-based behavioral economics interventions. Traditional economics theory predicts patients will adhere to their prescriptions when the long-term benefits of doing so outweigh the short-term costs. In other words, this theory suggests patients will pay a relatively small monetary fee today for a medication that will produce relatively large health benefits in the future. However, this theoretical perspective does not take into account the behavioral economics of intertemporal choice or, more specifically, delay discounting. The short-term beneficial consequences of medication adherence often go unnoticed. Consequently, patients may not recognize the benefits of adherence for many weeks, months, or years after they start taking a drug. In a systematic review of adherence studies, the mean rate of medication adherence was 76 percent among patients with physical disorders compared to 58 percent among patients with psychiatric disorders.