The evolution of public policies in the United States has been characterized as a process involving long periods of stability followed by abrupt episodes of substantial change. In this project, we identify strands in the literature and synthesize policy theories into a policy regime model useful in explaining both stability and change. This model focuses on power arrangements, policy paradigms and organization - factors that operate to maintain long periods of stability. We demonstrate how stressors - catastrophic events, economic crises, demographic changes, shifts in modes of production, and others - impact policy regimes and create pressures for change. We argue that the process of policy regime change - the abrupt episodes of substantial change - occurs with changes in the policy paradigm, alterations in patterns of power and shifts in organizational arrangements. The old policy regime disintegrates and the new one emerges with a new policy paradigm, new patterns of power and new organizational arrangements that operate to maintain long periods of stability.