In this introduction, the editors suggest a framework for the study of globalization and environmental governance, review important contemporary developments in supranational environmental governance, and introduce individual contributions to the special issue. Held, McGrew, Goldblatt, and Perraton's distinction between hyperglobalist, skeptical, and transformationalist perspectives on dynamics of globalization is useful in the study of the transformations in environmental governance around the world today. Three important innovations are examined: the development of supranational environmental institutions, increased use of market-based regulatory instruments, and the rise of global civil society involvement. Emergent transformations in global environmental governance are not inevitable, and neither are they sufficient for sustainability. Rather, they are constantly threatened by the interests and actions of economic actors and constrained as well by politics, geography, and global inequality. Persistent efforts by interested parties are required to retain salience, maintain momentum, and extend effectiveness of the new forms of environmental governance.