Terfezia, Picoaand Tirmania, so called desert truffles, are mycorrhizal fungi mostly endemic to arid and semi-arid areas of the Mediterranean Region, where they are associated with HELIANTHEMUM and Carex SPECIES. The aim of this work was to study the identification, molecular analysis, distribution and hosts of these pezizalean hypogeous fungi in Iran. Among the specimens, Terfezia claveryi, Tirmania pinoyi, T. nivea, Picoa lefebvrei and P. juniperi were identified. Field, laboratory and anatomical studies showed that HELIANTHEMUM ledifolium, H. salicifolium, H. lippi and Carex stenophylumhave ectomycorrhizal associations with five SPECIES in the studied areas. The results of molecular analysis showed that C. stenophylum roots form mycorrhizal associations with T. claveryi. Hyphal mantle was absent from sections of the mycorrhizas. The results of physico-chemical analyses on soil samples from different parts of the Fars Province in Iran showed that the genusTirmania was more prevalent in soils with high CaCO3 and silt contents than the T. claveryi, P. lefebvrei and P. juniperi. The Canonical Correspondence Analysis (CCA) indicated that soil structure were an important environmental parameter influencing desert truffles distribution.