The study of the adoption of activities to protect the natural environment has tended to focus on the role of organizational fields. This article advances existing research by simultaneously examining conflicting processes that operate in nested organizational fields at local, national and supra-national levels. It examines the recent spread of an environmental program for reducing emissions of greenhouse gases among local governments in three countries: United States, Canada and Australia. Qualitative data is used to identify the main factors that contribute to municipalities' decision to adopt this program, while event history analysis is used to test hypotheses regarding the effect of local governments' attributes, as well as of ties to state and global associations. Results show that widespread adoption of this environmental program is contingent on the development of national change agencies. (Contains 1 figure, tables and 24 notes.)