This chapter discusses the Latin American subsystem in terms of criteria applicable to any international regional subsystem with subregional components. It traces that subsystem change, has a dual concern: Latin America’s position in global politics, including external influences on Latin America and the various subregions; and relationships among the Latin American states themselves. The chapter emphasizes the last element—structure and change in the international system and in the Latin American subsystem as indicated by patterns of power distribution among the actors. Scholars have proposed differing definitions of regional subsystems, and their work on related issues is marked by conceptual disparity. In studying a particular regional subsystem, one must first identify the boundary that delimits the region and sets it apart from other components of the larger international system. Identification of the regional line of demarcation begins with the notion of a geographic boundary delimiting the region and enclosing a set of physically proximate states.