Research by social choice theorists has revealed much about the fundamental properties of institutions such as legislatures and voting systems. Almost no attention, however, has been paid to the properties of institutions such as bureaucracies. This essay attempts to lay the foundation for a social choice theory of bureaucracy. First, the properties of decentralized bureaucracies, which stress the importance of expertise in decision making, are illuminated through application of a theorem by A. K. Sen. Sen's theorem suggests that decentralized institutions are susceptible to several different kinds of problems. Next, it is shown that adding some degree of hierarchical does not solve these problems: hierarchies are prone to the same kinds of problems as decentralized institutions. Thus it appears that the design of a bureaucracy requires making some unpalatable trade-offs among several desirable, but incompatible, organizational principles. Sen's theorem points out the kind of research necessary to understand the full implications of these trade-offs. Bureaucracies are usually expected to conduct their affairs according to a variety of procedural and substantive standards. First and foremost, decisions are to be based on technical expertise. This accounts for the near universal employment in bureaucracies of scientists, technicians, or other experts. But knowledge about any particular problem is seldom complete, and in a competitive or changing environment there may be advantages to making some decision, however imperfectly grounded on expertise, rather than none at all. This accounts in part for the hierarchical structure of bureaucracies. In the absence of expert knowledge some chief executive is given authority to impose his own best judgment on the matter. Expertise and decisiveness are of course not the only standards. As Wilson (1967) noted, bureaucracies are also expected to be efficient in their activities, to maintain fiscal integrity, and to be accountable to responsible officials. Public bureaucracies are further expected to make equitable decisions, that is, to treat people with the same kinds of problems in the same kinds of ways. They may also be expected to be responsive to the unique needs and concerns of those dependent on them. They are sometimes even required to make decisions via legally defined standards of due process.