The expert workshop on "Measuring the Impact of Peacekeeping Missions on Rule of Law and Security Institutions" was organized by the United Nations Department of Peacekeeping Operations, in collaboration with DCAF and with support from the Governments of Switzerland and the United Kingdom. The objectives of the workshop were to seek expert advice on how DPKO's Office of Rule of Law and Security Institutions could assess the impact of both headquarters and field-based rule of law and security institutions-related initiatives. A crucial message emerging from the workshop was that while there are numerous challenges to measuring impact, these should not inhibit evaluations that support lessons-learning and enhance accountability.