Counting forced migrants runs into a number of hurdles related to their classification, to their experience of flight, and to the need to use myriad sources of data from governments, international organisations, and non-governmental organisations. To complicate matters, three organisations have mandates to count different groups - The un Relief Works Agency (UNRWA) for Palestine refugees, the un High Commission for Refugees (UNHCR) for refugees more generally, and the Internal Displacement Monitoring Centre (IDMC) for internally displaced persons (IDPS). All three face a range of common challenges in carrying out this vital aspect of their respective mandates. These include conceptual challenges, political concerns, competing interests and access. They also face their own political and institutional challenges, leading to individualised approaches and variance across and even within the organisations. In spite of these complexities, there have been significant improvements in the reliability of data and new technologies and registration methods are providing a way forward to a better understanding of forced migrant movements.