In the first detailed study of how a major environmental NGO works transnationally, Brian Doherty and Timothy Doyle examine the relationships between the 74 national organizations of Friends of the Earth International. Drawing from a rich mix of survey data, interviews, archival sources and access to internal meetings, they show how FoEI has developed a distinctive international environmentalism, which allows for the differences in context between regions and across the North-South divide. Following the expansion of FoEI into the global South, the challenges it then faced over questions of ideology, organization and campaign strategy are examined over a twenty year period. The book demonstrates the development of an FoEI tradition of solidarity which accounts for its ability to overcome internal crises and pursue joint campaigns despite conflicting understandings of politics between its national organizations.