This is a unique compilation on the use of leaching/extraction methods in different fields. The use of leaching test methods is increasing in various areas including: waste treatment and disposal; incineration of waste; soil clean-up and reuse of cleaned soil; sludge treatment. This has led to (and may increasingly lead to) the development of a large number of very similar tests in these different fields. However, these developments are taking place with no clear understanding of their mutual relationships. In view of these developments, efforts are needed to harmonize the leaching procedures that could be adapted for different matrices, as well as validate the use of existing tests in other fields. The development of a wide variety of leaching/extraction tests for different matrices is undesirable from a regulatory point of view and undesirable for industry. Clarity in testing is crucial in producer-consumer relations. This collective document will assist in improving the understanding of leaching from a variety of sources and will, where appropriate, help to bring together the approaches used in different technical fields and in different countries.