This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book discusses the US international environmental policy in the context of the United Nations Conference on Environment and Development (UNCED) process. It focuses on the formative stages of UNCED process, especially as it relates to international equity and US foreign policy, but it also looks at how and why US policy has evolved since Rio de Janeiro. The UNCED agreements and conventions signed at the June 1992 Earth Summit held in Rio elevated norms of international equity to prominence in the environmental issue area. During UNCED negotiations on the Biodiversity and Climate Chang Conventions, the United States experienced internal dissension over appropriate policy. Ideas like international equity can become rooted and take on a life of their own in international relations, possibly becoming important determinants of—or at least constraints on—state behavior.