Concern over the structure and design of organizations has traditionally dominated the study of public administration. The focus may result from the absence of any readily quantifiable measures of organizational performance – such as profit – in public organizations, so that greater attention must be devoted to practical and theoretical questions of organizational design Moreover, the responsibility of public organizations to external political actors and institutions, and the general opprobrium associated with the word “bureaucracy” also have placed pressure on public administrators to design the perfect organization. For whatever reason, public administration has been almost obsessed with con structing the best organizational structures for implementing public programs (see Hult and Wolcott, 1990; Weimer, 1995). The tendency to focus on structural solutions for the problems of public administration reached one zenith during the 1920s and 1930s with the presumably scientific theories of administration, dismissed by Simon (1947) as the “proverbs of administration,” advocating concepts such as unity of command, span of control and POSDCORB management (Gulick and Urwick, 1936). The 1980s and 1990s have been another high point in the search for the best possible forms of administrative structure. The reforms implemented in this period have had a number of procedural and behavioral elements, but they also had a strong structural component (see Chapter 9). In addition, the structure of the public sector depends very significantly upon history and economic and social conditions, as well as upon ideas about the purposes of government. The reform of government is a common activity, but no reform, however well informed by organization theory, is likely to be able to overcome all the inherited traditions embodied within the machinery of government in any society (Painter and Peters, forthcoming). Unless that macro level of organizational constraint is understood, any attempt to alter the character of the internal functioning of the organization is doomed to failure. This chapter has two objectives. The first is to describe in a brief fashion five major administrative systems, representing a range of variation along a number of dimensions of public administration. These descriptions should provide the reader with some basic information about how administrative systems are structured, and how various components fit together to form a more or less coherent whole. Second, the chapter will examine several points concerning governmental structures that are raised by organizational theory and assess the responses made by governments as they structure and restructure their administrative systems. The range of these answers can be used to gain a better idea about the relationship of organizational structure to the functioning of the public sector.