ISO 17402:2008 provides guidance for the selection and application of methods to assess bioavailability for the characterisation of contaminated soil and soil materials. ISO 17402:2008 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.The contaminants considered in ISO 17402:2008 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). ISO 17402:2008 can also be applied to sediments.