This chapter examines the role of impact assessment in shaping the field of transitional justice. Through exploring the origins and meaning of impact assessment, it raises questions about the agendas and challenges posed by those funding and conducting this research. The chapter provides a summary overview of examples of impact assessment, ranging from victim studies, community studies and institutional assessments to public opinion surveys and international comparative research in order to demonstrate the scope encompassed by such endeavours. These serve to demonstrate the centrality of impact assessment in guiding policy, but also raise important questions about how research is itself positioned in relation to transitional justice politics.