This chapter aims to build analytical and empirical bridges between the growing literature on performance and performance measurement, and the study of the European Neighbourhood Policy (ENP). It discusses various approaches to, and perspectives on, performance drawing mostly on the literature on public administration and organisational studies. The chapter reviews the European Union studies scholarship showing that research on performance, though on the rise, falls short of a systematic effort across different issue areas. It outlines five indicators for performance measurement – relevance, cohesion, effectiveness, impact and resilience – and discusses their application in the context of the ENP. The most commonly used indicators to measure performance of public or private agencies are the 'three Es' –economy, efficiency and effectiveness. Examining performance in relation to cohesion refers to the ability to articulate policy preferences consistently and to the consistent alignment of common policies among stakeholders, horizontally and vertically.