It may seem odd to claim that the modern-day economics of organization actually pays far too little attention to institutions. Although its subject is itself an institution—the firm and its various alternatives—the economics of organization does not make much analytical use of institutions in the wider senses. This observation is related to the much more common claim that the economics of organization does not make adequate use of history. By contrast, the literature on business groups around the world is thick with both institutional and historical detail. This article discusses the economics of organization and the economics of institutions more broadly, and suggests the ways in which those theoretical strands can help to organize the institutional and organizational facts about business groups. It also examines the ways in which the facts about business groups can influence how people think theoretically about the boundaries of the firm.