These papers review and analyze mediation efforts around the world to extract lessons learned. Drawing on extensive fieldwork, they also make concrete recommendations to the UN on how to design and enhance its mediation capacities. The first set of papers (2014–2016) focuses on UN-led mediation processes. The second set of papers focuses on mediation processes where the UN did not play a lead role but supported specific aspects of negotiations or implementation of agreements. Several of these papers are available in French or Spanish.