There is an emerging realization that responsible management of chemicals requires a quantitative understanding of emissions, transport and fate and degradation processes in the environment. The most convenient way to demonstrate this understanding is with a verifiable contaminant mass balance compiled with the aid of an environmental fate model. --This seminar will describe the development and application of mass balance contaminant fate models on regional, national and continental scales. Models for Canada and the North American Continent that exploit linkages to Geographical Information Systems (GIS) software will be described. Through a series of case studies, the ability of these models to quantitatively describe the emission-to-environmental concentration relationship for chemicals will be demonstrated, and the prospects for extending the analysis to include a description of human exposure to environmental contaminants discussed.