As rational choice theory has moved from economics into political science and sociology, it has been dramatically transformed. The intellectual diffusion of agency theory illustrates this process. Agency theory is a general model of social relations involving the delegation of authority, and generally resulting in problems of control, which has been applied to a broad range of substantive contexts. This paper analyzes applications of agency theory to state policy implementation in economics, political science, and sociology. After documenting variations in the (...) theory across disciplinary contexts, the strengths and weaknesses of these different varieties of agency theory are assessed. Sociological versions of agency theory, incorporating both broader microfoundations and richer models of social structure, are in many respects the most promising. This type of agency theory illustrates the potential of an emerging sociological version of rational choice theory. (shrink)