Subsystems developed as a solution to the problem of making policy in the rough and tumble world of the American polity. Whirlpools, iron triangles, capture, issue networks, sloppy large hexagons, presence politics, and advocacy coalitions have all been offered as subsystem-based frameworks of analysis. The rationale underlying the formation of a subsystem is that it allows subsystem members to shun competition for control and predictability. The dominant-coalition approach, however, assumes subsystem policy decisions are routinely approved by actors in the larger political system. Competitive coalitions can be distinguished from dominant coalitions by the increasing diversity of interests involved in subsystem deal making. Dominant coalitions are subsystems in which the policy minuet is danced to a tune composed almost exclusively by subsystem participants. The iron triangle variation of subsystem theory argues that subsystems develop as a means of distributing the spoils of the policy process. The chapter also presents an overview of the key concepts discussed in this book.