This chapter focuses on adaptations in the context of dissemination and implementation research and practice. Consistent with the existing literature, the authors recommend that adaptations be proactively and iteratively determined, strongly informed by a variety of stakeholders, and that efforts be made to carefully describe and document the nature of the adaptations and evaluate their impact on desired service, health, and implementation outcomes. While this chapter focuses on adaptations to interventions and the context of practice, the authors also note that adaptations may need to be made to implementation strategies. Following the call by Proctor and colleagues for further precision in defining and operationalizing implementation strategies, and based on evidence that scholars are not necessarily reporting what and how they are adapting the interventions, scholars are urged to define and evaluate the adaptations they are making not only to the interventions and context of practice but also to the implementation strategies.