Exposure evaluation is an integral component of the risk assessment process linking chemical contact to toxicologic manifestation or disease outcome. When exposure data are used to make decisions in the absence of corroborating data or disease outcome, human risk assessments rely on conservative assumptions that may overestimate true risk. A major theme of the symposium was that conservative assumptions in risk assessment could be replaced and uncertainties reduced as data on exposure assessment are coupled with health effect outcomes. Many of the uncertainties associated with exposure assessment are the result of a lack of measurement techniques, lack of understanding of differences in human susceptibility, interindividual variation, and differences in absorption, fate transformation and disease processes. Basic research and collaborative studies are needed to develop techniques, models, and data to reduce these uncertainties. Other important themes that emerged from the symposium are that social issues are as important as scientific issues in conducting effective exposure assessments, and that decisions will be made regardless of data availability or quality.