We opened this chapter with a broad definition of the concept of policy advocacy encompassing many actors and approaches. However, the focus of the guide is specifically centered on advocacy to improve evidence-based decisionmaking, and more specifically research-based evidence. Therefore, in this section we take a deeper look at the process of how research evidence feeds into the decision-making process. The intention is to give an overview of this admittedly messy process and then to consider the nature of advocating a research-based position to achieve a particular result. This provides the foundation for the next chapter where we examine four in-depth cases of research-based policy advocacy and extract key approaches and lessons learned.