Edible Ectomycorrhizal Mushrooms (EEMMs) live in the soil in association with the roots of plants, other ectomycorrhizal fungi and soil organisms, all of which compete for space and nutrients. Consequently, the success of introducing an Edible Ectomycorrhizal (EEM) fungus into soils with the intention of cultivation is entirely dependent on its ability to survive in this competitive environment. Studies on the composition and structure of Ectomycorrhizal (EM) communities in both productive and non- productive EEMM areas have contributed to a better understanding of the relationship that EEMMs establish with other EM fungi and the environment. These have included morphological studies, the use of molecular tools, and most recently metagenomic methodologies leading to new insights into soil EEMM ecology. In this chapter, we briefly describe the methods that have been used to study EM fungal communities and web databases that can be used for the identification of ectomycorrhizas such as the recently released eMyCo. We also illustrate the studies that have been conducted on the EM communities in natural and cultivated ecosystems where the most important EEMMs are found.