This volume presents the proceedings of a symposium on the Environmental Monitoring and Assessment Program (EMAP), held in Albany, NY, USA, in April, 1997. A research program of the U.S. Environmental Protection Agency, EMAP has been advancing the state of the science in ecological indicator development, statistical sampling design, landscape characterization, and other tools of environmental monitoring since the program's inception in the late 1980s. EMAP's goal is to develop and demonstrate the science necessary to monitor status and trends in the condition of ecological resources at multiple spatial and temporal scales. These proceedings feature the latest research on ecological indicators, plus results from seven years of EMAP monitoring in estuarine, forest, and freshwater ecosystems. Contributors to this volume have worked closely with EMAP or are conducting related research within U.S. federal and state environmental agencies and academic institutions. Chapter topics include causal relationships, landscape ecology, carrying capacity and sustainability, statistical issues in large-scale surveys, and approaches to integrating data from multiple scales and media. Publication of these proceedings is intended to facilitate the development and application of techniques for ecologically based assessments of environmental condition in the US and abroad.