The largest corporations in the world are increasingly adopting international corporate responsibility (CR) reporting standards from organizations such as the Global Reporting Initiative to meet stakeholder expectations for reliable and comparable social and environmental performance data. At the same time, significant geographic variations in reporting rates remain. The goal of this paper is to explain the diffusion of international CR reporting standards within the Americas. Reporting rates cannot be explained fully by a country's population size or level of economic development. Based on a unique statistical analysis of the relative impact of institutional environments, corporate resources and strategic orientation, stakeholder pressures, and transnational trade and learning networks, this research concludes that the diffusion of CR reporting throughout the Americas to date has been fueled by a rather narrow set of corporations with the capacities necessary to implement CR reporting and the strategic orientation to benefit from it. Moreover, corporations' internal capacities and the external demands for CR reporting have been enhanced in select countries by national and transnational CR advocacy and training organizations. This has led to an uneven development of CR reporting thus far, and this unevenness is expected to continue even as overall reporting rates increase.