This report explains the conditions under which governments might promisingly negotiate with terrorist groups so as to end their violence. It is drawn from a larger United States Institute of Peace–supported multiyear research project on how terrorist campaigns meet their demise. Based on qualitative and quantitative research that explores the lessons of negotiations with terrorist groups and analyzes other potential pathways for a group’s decline, including decapitation, repression, reorientation, and implosion, the conclusions herein offer general guidance to policymakers who must decide whether to enter talks with a given terrorist group. The report applies those lessons specifically to the current debate over negotiating with “al-Qaeda” and “the Taliban.”