The science of exposure assessment has been expanding both its theoretical and experimental bases over the past two years. Recent theoretical work published by the authors in the Journal of Exposure Analysis and Environmental Epidemiology (Volume 4, Number 3, 1994) has defined a multistep process to couple measurement data with mathematical models of exposure and dose. The present manuscript discusses the need for improving the measurement of exposure in order to reduce uncertainties in the potential risk and, eventually, the occurrences of health outcomes in the community environment. The discussion focuses on hazardous waste sites and how improving or routinely introducing exposure measurements to the remedial investigation can lead to a better understanding of how the potential population can get exposed via single or multiple activities. This information can help to better understand the need for specific remediation actions and selection of the types of models that can be used to predict exposure for a large population and to estimate the reduction in postremediation exposure for a local population (National Research Council, 1991).