The January 2011 referendum on self-determination could result in Sudan’s partition, and the country’s North-South border may ultimately become the world’s newest international boundary. The 2005 Comprehensive Peace Agreement (CPA) that ended two decades of civil war called for the border between the North and the semi-autonomous South to be demarcated within six months. Five years later, the task remains incomplete. The sooner the parties break the border deadlock the better, though the process need not necessarily be completed prior to the referendum as Khartoum has argued previously. Furthermore, a solution to the border is about not only drawing a line, but also defining the nature and management of that border and the future relations of communities on both sides. A “soft” boundary is ideal, one backed by a framework for cross-border arrangements and, if necessary, safeguarded by a joint monitoring mechanism. Progress toward both demarcating and defining the border will prevent it from becoming a source of renewed conflict in the post-CPA era.