A policy process framework that has been developed to simplify the complexity of public policy is the advocacy coalition framework (ACF). This essay reports on an analysis of 80 applications of the ACF spanning nearly 20 years. The review shows that the ACF is applicable to various substantive topics, across various geographical areas, and with other policy process theories and frameworks, including the stages heuristic. The most commonly tested hypotheses involve policy change, learning, and coalition stability. Although the hypotheses tend to be confirmed, questions remain about the membership, stability, and defection of coalition members; about the causal mechanisms linking external events and policy change; and about the conditions that facilitate cross-coalition learning. Emerging areas of research include policy subsystem interdependencies and coordination within, and between, coalitions.