Expatriation, as an integral part of the employment conditions of the International Civil Service, has its origins in the League of Nations and ILO and before that, in the personnel practices of colonial civil services in the late nineteenth century. The Preparatory Committee of the United Nations borrowed heavily from the policies of the League when developing the post war concept of an international civil service. Thus, a pay “margin” for expatriate service, education benefits for dependent children and home country travel were all based on the League’s practices. The creation of the UN and the first group of Specialised Agencies generated a review of conditions of service by the 1949 “Flemming Committee”, which reported its findings to the Fourth Session of the General Assembly. The Flemming Committee provided basic justifications for the major elements of expatriate service that are, in the main, still valid today. Both the Flemming Committee and the League of Nations were, however, concerned with a career service in highly centralised organizations located in mono-cultural environments. The 1960s saw the expansion of the international civil service into multiple locations, mainly in Africa, Latin America and Asia. Consequently, the conditions of service, previously defined for centralised organizations, had to be adapted to allow for greater flexibility. The 1980s then saw another extension of the concept of expatriation with a need to rotate staff from one assignment to another and to respond quickly to ever-increasing demands for humanitarian and development assistance.