The current international framework for protecting migrants and refugees is often criticised as being fragmentary, with a multiplicity of categories of persons, and of organizations for addressing their problems. Many scholars have called for a new international regime and a more unified institutional arrangement, which would provide for the orderly movement of people. The basic weakness of the current regimes derives from the artificial distinction between 'refugees' and 'migrants' created after the Second World War. The article explores the institutional origins of the system and determines the major causes of the different treatment of refugees and migrants.The paper argues the following: First, the system, which might be in need of reconstruction in order to suit today's world of high mobility and diversified patterns of international movement, resulted from the battle between the United States and the international institutions (the ILO and UN). The conflict was over how to deal with the surplus populations in Europe. The US favoured an institution with specifically designed functions based on inter-governmental negotiations. The ILO-UN plan recommended international co-operation under the leadership of a single international organization. After the conferences in Naples and Brussels in 1951, the US plan was accepted and the Provisional Intergovernmental Committee for the Movement of Migrants from Europe (now renamed the International Organization for Migration) was created. Second, the distinction between migrants and refugees also emerged as a way of helping the restructuring and dissolution of the pre-war refugee protection organisations. Two parameters for the division -forced movement and violation of civil and political rights -appeared inadvertently rather than deliberately. From the perspective of the US government, the main goal was to limit international influence over national migration and refugee policies as much as possible.