Oral ingestion of soil and dust is a key pathway for human exposures to metal and metalloid contaminants. It is widely recognized that the site-specific bioavailability of metals in soil and dust may be reduced relative to the metal bioavailability in media such as water and food, and adjustments for oral relative bioavailability are becoming more accepted. Both animal models and 'in vitro' bioaccessibility models have been used to estimate relative bioavailability of metals in soil and dust. Although animal models are often considered the 'gold standard', they may be costly or otherwise prohibitive at certain sites and may not be sensitive enough to test environmentally relevant samples for all contaminants. Routine application of 'in vitro' metal bioaccessibility models in regulatory settings is being held up by different perceptions of what is required of these models in terms of validation. This symposium provided the opportunity for international experts to exchange their views on methods for assessing relative bioavailability/bioaccessibility for application in risk assessments at contaminated sites. The symposium speakers presented recent developments in animal models, new 'in vitro' models, the role of mineralogical analyses in assessing relative bioavailability, and the application of physiologically based models as research tools. In addition, two panel discussions addressed specific research questions and discussed future research needs in this area. Recognizing the multi-disciplinary nature of exposure assessment, this symposium included representation from many disciplines including risk assessment, toxicology, environmental geochemistry, geology, soil, and analytical chemistry from the U.S., Europe, and Canada.