This in-depth study on the reintegration of internally displaced people (IDPs) returning to Southern Sudan and the Three Areas in the wake of the signing of the Comprehensive Peace Agreement (CPA) was initiated by the United Nations Mission in Sudan’s Return, Reintegration and Recovery Section (UNMIS/RRR), with the specific aim of informing future strategic planning on how best to support return and reintegration over the coming year. The study seeks to understand key determinants of sustainable reintegration and the role of different actors in achieving this goal. It focuses on key obstacles to, and opportunities for, successful and peaceful reintegration, paying attention to different interventions (implemented by federal and state governments, by UNMIS and by other international agencies), and the extent to which these have addressed obstacles or harnessed opportunities.