The concept of a transnational system applies well to a study of labor in North America. For one thing, the chief characteristics of the labor market and of the institutions, procedures, and practices of labor relations are broadly similar in Canada and the United States as compared with other parts of the world. Although such similarities are not alone sufficient to suggest a system, there is also a persistent structure of relationships and interactions in labor matters extending across the boundary between the two countries. American investment in Canada and the so-called international unions are at the heart of this structure of relationships. Other segments of labor, whether organized in trade unions or unorganized, are connected with the heart of this transnational system through the continental flow of economic transactions.