Standard economic theory fails to address the economic and political significance of modern multinational corporations. In this module explanations of firm growth based on economies of scale and scope are supplemented with a discussion of the transnational mobility and influence of large corporations. The social and environmental responsibilities of multinationals are considered, with an emphasis on externalities and the need for a “triple bottom line.” The module concludes with a discussion of ways to encourage large firms to adopt goals that are aligned with the broader goals of society.