Editors' Summary: From June 1 to June 12, 1992, the United Nations (U.N.) Conference on Environment and Development, commonly referred to as the Earth Summit, is scheduled to meet in Rio de Janeiro, Brazil. This conference has been hailed as a "constitutional convention" for the global environment. Conference organizers estimate that 15,000 representatives from more than 150 nations will participate. Issues on the agenda include such high-profile topics as climate change, forest conservation, and biodiversity. The authors discuss the background of the conference, beginning with the U.N. Conference on the Human Environment held in Stockholm, Sweden, in 1972. They review the U.N. preparatory committee meetings that have been held in preparation for the Rio conference, and review the principle items on the agenda. The authors next analyze the subjects of contention among the countries and regions that are expected to be the main players at the conference and in future international negotiations on global environmental problems. The authors conclude that it is still too early to predict the outcome of the conference. Although the negotiations leading up to the conference indicate that there is much disagreement on fundamental issues, the amount of public attention generated by the preparations for the conference at least raise hopes that the Earth Summit will produce some positive steps toward a new environmental world order.