This article reviews and synthesizes the uses of expert-based information in policy subsystems. The review begins by summarizing the different uses of information in the multiple streams theory, the punctuated equilibrium theory, the social construction theory, and the advocacy coalition framework. Three uses of expert-based information are identified as instrumental, learning, and political. The three uses of expert-based information are then compared across unitary, collaborative, and adversarial policy subsystems. This article synthesizes the findings in a set of propositions about the use of expert-based information in policy subsystems and about the factors that contribute to shifts from one policy subsystem to another.