About two decades ago, Paul Sabatier (1991) urged scholars to develop better theories and empirics for understanding policy processes. Sabatier's proposition, in collaboration with Hank Jenkins-Smith, became the advocacy coalition framework (ACF). The original version of the ACF sought to make important contributions to the policy process literature by responding to several perceived needs: a need to take longer-term time perspectives to understand policy change; a need for a more complex view of subsystems to include both researchers and intergovernmental relations; a need for more attention to the role of science and policy analysis in public policy; and a need for a more realistic model of the individual rooted more deeply in psychology rather than microeconomics. This article introduces a special edition of this journal that offers a collection of eight ACF applications that continue to test and develop the theories within the framework. Adapted from the source document.