Twenty years after the landmark Stockholm Conference on the Human Environment in 1972, the United Nations has convened a Conference on Environment and Development (UNCED) in Rio de Janeiro in June 1992. The 1989 UN resolution calling for the conference singles out -- among other global problems -- issues of biodiversity, water and other natural resources, atmospheric integrity, and human health as ones whose management requires strengthened international cooperation and attention. Whatever explicit and effective commitments -- to control greenhouse gases that threaten global warming, for example -- are negotiated at UNCED, profound problems relating to the linked pursuit of environmental, natural resource, and economic objectives are certain to survive the two-week meeting of government leaders, technical experts, and representatives of environmental constituencies. To be sure, participants may well assert that the goals of environmental protection, natural resource adequacy, and economic growth are compatible. But a probing of the question of sustainability of development inspires less confidence that potential problems and conflicts in the pursuit of these goals are fully appreciated in the international community, much less that the consensus needed to easily achieve the goals will be forthcoming. In Global Development and the Environment: Perspectives on Sustainability, researchers at Resources for the Future examine some of the enduring issues, whether or not officially under consideration at the conference or raised there informally, that cannot be ignored in any attempt to pursue aspirations concerning the environment and development. The lasting value of UNCED may depend on the extent to which it diverse participants couple political rhetoric with willingness to confront these difficult issues once this 'earth summit' fades into history.