This thesis seeks to promote a clearer understanding of relationships between trade liberalization and environmental quality in a free trade zone along an international border, between countries unevenly matched in development and infrastructure. Specifically, it examines whether theories of environmental degradation provide appropriate models for explaining the impact of NAFTA on the environment in the Paso del Norte. The relationship between trade liberalization and environmental quality is examined through an analysis of environmental indicators in the decade preceding and following NAFTA. Finally, the role of environmental governance is addressed, especially the intricacies involved in multi-jurisdictional governance of the environment. The research indicates that trade liberalization is not necessarily environmentally harmful. The data suggest that NAFTA had little to no direct negative impact on the region's environmental condition, but they also do not provide evidence that NAFTA improved the environment. One factor that could have helped to limit its effects may be local, interstate, and international initiatives that improved the health of the ecosystem along the border before NAFTA was even conceived. Another factor is the environmental governance in place before and after NAFTA. Thus, it may be beneficial for trade liberalization agreements to address environmental concerns as integral parts of the negotiations, and to set requirements for meeting infrastructure demands, as the agreements are implemented. Furthermore, it is important that international environmental institutions established to monitor environmental cooperation be more closely associated with the trade cooperation organizations and be given the authority needed to complete their directives more effectively.