Institutionalism has become firmly entrenched in legal scholarship.1 In particular, institutionalism has become a powerful and alluring theoretic for international law scholarship. Given the use of institutionalism in international law scholarship, and the importance of international economic organizations to theory and practice, it is natural that institutionalism has been prominently used to scrutinize international economic organizations, including the World Trade Organization. When international law scholars utilize the tools of institutionalism, however, they tend to draw only from two sources. International relation's regime theory3 has entered the mainstream of international law discourse, and has been applied directly to the World Trade Organization. Institutional economics,4 particularly transaction cost analysis, has also appeared in international law discourse, and has been directly applied to organizations that include the World Trade Organization. Regime theory and institutional economics, however, do not exhaust the universe of sources of institutional analysis. Virtually all of the social sciences are experiencing a revival in institutionalism.) In particular, this Article examines two schools of institutionalism: historical institutionalism, 6 vvhich is a ? roduct of political science; and sociological institutionalism, which is a product of sociology. Each of these iterations of institutionalism differs in critical ways from regime theory or institutional economics. Each also provides a rigorous framework for analyzing international law and for scrutinizing the World Trade Organization. To date, however, neither international law scholars nor trade scholars have availed themselves of these two means of inquiry. This lack of use raises an interesting question, which is analyzed in this Article: why have international law scholars and trade scholars not utilized historical institutionalism or sociological institutionalism? Ironically, historical and sociological institutionalism themselves provide insights. Historical institutionalism emphasizes path dependency: a brief review of the unfolding of institutional thought in international law scholarship reveals how regime theory and institutional economics obtained an advantage over rival schools. Similarly, sociological institutionalism emphasizes cultural factors in the creation or alteration of institutions: the culture of legal scholarship may not be conducive to these versions of institutionalism. The implications for both trade scholarship and the World Trade Organization as institutions are significant. Understanding why trade scholarship has not incorporated historical and sociological institutionalism may explain why trade scholarship has not established linkages with other potentially instructive schools of thought, such as business ethics. Moreover, understanding the World Trade Organization as an institution8 with a history and embedded in culture may explain why practical linkages, such as the linkage between trade and human rights, are difficult to accomplish. Before discussing the possibilities that accrue from understanding the relationship between trade scholarship and historical and sociological institutionalism, the current linkage between trade scholarship and institutionalism must be explained. This article begins with a discussion of institutionalisms that have been used to analyze the World Trade Organization.