The complex nature of many health care interventions poses challenges for successful replication. This article presents insights on tackling these challenges primarily drawn from recent research and programs in the UK. These insights include the need to codify complex interventions in ways that reflect their social, context-sensitive, and dynamic nature; to capture learning as the intervention is implemented in new contexts; and to design programs in ways that respect adopters' role in the spread process. We argue that program leaders should have familiarity with theoretical approaches for conceptualizing complex interventions, that a discrete testing-and-revision phase should be recognized as part of the spread process, and that programs should be designed in ways that build and sustain adopter commitment. These perspectives complement the traditional focus on the innovator in models of spread by highlighting the role adopters play in adapting interventions and generating learning, and they have implications for the design of programs to spread innovation.