The conflict in the Lake Chad Basin (LCB) region, which affects large parts of Nigeria, Cameroon, Chad and Niger, has displaced 3,0125,239 Internally Displaced Persons (IDPs) in the last decade. During that period, Boko Haram and the Islamic State in West Africa Province have perpetrated numerous attacks on security forces and civilians, exploiting community grievances over the lack of governance and public services (including education, health, justice, water, etc.) While new displacements continue to take place, some areas have become more stable, and have seen the return of displaced persons. As of May 2021, 1.75 million individuals have returned to their location of origin in the LCB region (in addition to the 3 million IDPs). In order to find durable solutions for internal displacement — whether through return to communities of origin, local integration, or relocation – and to prevent new displacements in the region, it is critical to understand the relative levels of stability in locations hosting returnees or displaced populations. To better measure this phenomenon and provide structured solutions, IOM has launched the Stability Index (SI), to evaluate the stability of areas hosting returnees or displaced populations in the LCB. The SI seeks to understand which factors influence a location's stability, in order to identify priority interventions for transition and recovery, with the goal of strengthening the resilience and stability in the conflict-and displacement-affected region. In practical terms, the Stability Index measures levels of stability and analyzes which factors are relatively more impactful on the decisions of population to remain in place or to move. The tool can serve as a measure of stability in targeted areas in the LCB to enable governmental authorities and partners to develop better strategies, and prioritize and plan resources in fragile, unstable areas for coherent and comprehensive interventions that link humanitarian, recovery, and stabilization approaches. While pilot SI surveys were carried out in Nigeria, Chad and Cameroon in 2019, the first round of a harmonized SI data collection in all four countries of the LCB took place in 2021. This report presents results from the March-April 2021 Stability Index round of data collection conducted in Cameroon, Chad, Nigeria and Niger.