This part of ISO 23611 specifies a method for sampling, extracting and preserving macro-invertebrates from soils, including the litter zone. The proposed method is a prerequisite for using these animals as bio-indicators (e.g. to assess the quality of a soil as a habitat for organisms). The main premise of this method is rapid assessment (completing the sampling of a plot in one or two days with only basic equipment and a small number of field assistants) in order to be able to address all the taxonomic groups of soil macro-invertebrates at the same time and in the same place. The Tropical Soil Biology and Fertility (TSBF) method has evolved and some modifications have been introduced in order to use it in temperate regions. The sampling and extraction methods in this part of ISO 23611 are applicable to almost all types of soil, with the exception of soils in extreme climatic conditions (hard, frozen or flooded soils) and matrices other than soil, e.g. tree trunks, plants or lichens. A sampling design is specified in ISO 23611-6.