This International Standard provides guidance for the selection and application of methods to assess bioavailability for the characterisation of contaminated soil and soil materials. This International Standard does not give a selection of the best applicable methods, but specifies boundary conditions and principles of methods to be used and gives the minimal requirements for the development of methods. The results obtained from such methods can be used as an estimate of bioavailability in a risk-assessment approach. In this International Standard, when the term “soil” is only quoted for simplification, the broader term “soil and soil material” shall be considered. The contaminants considered in this International Standard are metals, including metalloids, and organic contaminants, including organometal compounds. This International Standard is also applicable to metals originating from natural geological and pedological processes (natural pedo-geochemical content). This International Standard can also be applied to sediments. NOTE An assessment procedure based on the bioavailable fraction of the total amount of contaminants in the soil or soil material can contribute to the development of regulatory requirements of risk-based assessment procedures for soils. According to the protection goals envisaged, applications of existing methods are recommended and their limitations discussed, with the intention of promoting the development and introduction of workable standard methods to be used in soil and site assessment. These methods are required to allow for the quantification of factors influencing bioavailability.