The Sustainable Development Goals (SDGs) built on and expanded a rich body of experience with targets and indicators associated with their predecessors, the Millennium Development Goals (MDGs). Yet in several respects, and in particular in Goal 16, the SDGs moved into uncharted territory, where agreement on the goal itself, and on the relevant targets and indicators, was difficult to achieve, and where the data itself was either very weak or non-existent. Goal 16 promised to promote peaceful and inclusive societies for sustainable development, provide access to justice for all and build effective, accountable and inclusive institutions at all levels. While a laudable ambition, it is extremely difficult to imagine what this means in practice, and how it could be measured either comparatively or longitudinally, as a guide to policy and programming. This chapter explores the broader challenge of monitoring and measuring the SDGs through the lens of SDG 16, beginning with a quick overview of the genesis of the goal itself, the selection of targets and indicators, and some of the debates around particular indicators. It highlights the exclusions and occlusions in the data, and what can (and cannot) be reliably measured, or even taken as a proxy for the goal. Finally, it reflects more broadly on the politics of measuring such things as the quality of governance, the level of violence, and abstract notions such as inclusivity or access to justice.