Mainwaring and Scully's concept of party system institutionalization (PSI) has greatly influenced the literature on parties and party systems. This article contributes to the “revisionist” literature on PSI by exploring the recent evolution of the concept's four dimensions in Chile. It finds that the Chilean party system is not homogenously institutionalized (as conventionally argued) but is simultaneously frozen at the elite level and increasingly disconnected from civil society. In this regard, it approaches some recent descriptions of the Brazilian party system, a prototypical example of an “inchoate” party system that has gained stability over time without developing roots in society. This article argues that the current operationalization of the concept of PSI is problematic. Not only should all four dimensions of the concept be simultaneously measured, probably through multiple indicators for each one, but their trends across time and space should also be better integrated into the concept's theoretical structure.