In a world that is changing rapidly and constantly, public administration needs to be able to respond as rapidly and as effectively as possible to new challenges and priorities. The process of reinvention and revitalization requires vision, knowledge and capacity. The same qualities are required from the United Nations if they are to assist developing countries and countries with economies in transition effectively in their efforts to reform public administration. This article provides an historical excursus of how the conception of the role of the state has changed in the past decades and its impact on developing countries; how instrumental the United Nations was in re-establishing awareness of the role of public administration in development, and the significant preparatory work done in this area by the International Institute of Administrative Sciences (IIAS). The article also illustrates how the United Nations Programme in Public Administration has reinvented itself in order to help reinvent government and singles out some of the emerging challenges in the field of public administration.