In-vitro gastrointestinal extraction, also known as oral bioaccessibility, is important when assessing chemical risk to humans. In use, it purports to simulate the release of chemicals from sample matrices (e.g., food and soil) that may be consumed intentionally or unintentionally in the diet, so in-vitro conditions are created to simulate, principally, enzymatic action in the mouth, the stomach and the intestines. This article reviews the current status of oral bioaccessibility in terms of the release of metals or metalloids from food and soil samples. We place particular emphasis on the parameters that influence gastrointestinal extraction, including gastric and intestinal pH, food constituents, residence time and particle size. It is clear that future development is needed to validate and standardize the methods.