The growing frequency and scope of externally supported security sectorreform processes has sparked demand for tools to assess changes in securitysector governance in states around the world. This paper takes a first smallstep towards this goal. By mapping the diverse indicator sets relevant forsecurity sector governance, it provides an overview of currently availabledata about the quality of security provision and security sector governanceamong states. In its first part, the paper specifies its understanding ofsecurity sector governance and discusses the uses and limits of qualitativeand quantitative indicators to measure security sector governance. Thepaper then provides a comprehensive overview of existing security- andgovernance-related indexes and assesses their contribution to measuringchange in security sector governance over time and across cases. Finally, thepaper’s extensive ‘source guide for security sector governance indicators’provides brief profiles of the discussed indicators and their data sources, andoutlines variations in the scope, coverage and methodology of the variousindicators.