This IDS working paper examines the role of knowledge in the process of making and implementing poverty reduction policy. It focuses on the production of poverty knowledge through measurement and assessment, providing an overview of contemporary poverty assessment approaches, and the issues and dilemmas involved in applying them in the context of poverty reduction policy processes. The first section examines the policy process in order to understand the relationship between poverty knowledge and policy change. It looks at how legitimate knowledge is traditionally framed in the policy process as the domain of technical experts who reduce complex phenomena to measurable variables, and how this frame changes if policy is understood as a more chaotic process with multiple actors involved. Section Two discusses the broad questions of what poverty actually is and how it can be measured, focusing on the fact that a consensus appears to have emerged which then obscures the many debates centred around poverty measurement. Three policy events are examined in order to show how different objectives shape the methodological choices policy actors make. The third section focuses on a range of methodologies available for poverty assessments, with a focus on household surveys and participatory poverty assessments (PPAs). Lastly, the World Bank and Oxfam are examined in order to understand how two international development actors with different objectives made use of acquired poverty knowledge in constructing policy messages. The argument is proposed that the agency and objectives of the policy actors themselves are most important in shaping policy narratives.