Society needs a quantitative and systematic way to estimate and compare the impacts of environmental problems that effect large geographic areas. This report presents an approach for regional ecological risk assessment that combines regional assessment methods and landscape ecology theory with an existing framework for ecological risk assessment. Risk assessment evaluates the effects of an environmental change on a valued natural resource and interprets the significance of those effects in light of the uncertainties identified in each component of the assessment process. The components of regional risk are defined, and the similarities and differences between regional and local risk assessment are discussed in this report. Unique and important issues for regional risk assessment are emphasized; these include the definition of the disturbance scenario, the assessment boundary definition, and the spatial heterogeneity of the landscape. We present an in-depth discussion of possible endpoints for regional assessments and criteria for judging endpoints. The nature of the assessment problem influences the appropriate choice of endpoints. A demonstration of a regional risk assessment is used to illustrate the components of the assessment framework, to test the utility of the approach, and to highlight unique aspects of regional assessment such as spatial heterogeneity, landscape pattern,more » and the need to link ecological systems through the use of models. 100 refs., 6 figs., 13 tabs.« less