Arbuscular mycorrhizal fungi (AMF) structures in roots of the naturally invading plant species and spore number in rhizophere soils of four coalmine overburden dumps (OBDs) ie 1-year, 5-year, 10-year and 15-year old after dumping and three adjacent natural forest (NF) sites ie NF-1, NF-2 and NF-3 of Tikak Colliery, Margherita, Assam were studied. The plant rhizospheres of coalmine overburden dumps and adjacent natural forest contained arbuscular mycorrhizal fungi (AMF). All thirteen naturally invading plant species on the OBDs investigated were positively mycorrhizal. AM fungal colonization in roots ranged from 15-82 per cent and AM fungi spores 100-1g rhizosphere soils ranged between 9-1771 comparatively more. AMF spores were recovered from OBDs compared to natural forest (NF) soils, except 1-year OBD. Coal mining reduces AMF status in younger OBDs. AMF spore number was found to increase with increase in age of the OBD and even more in number in rhizopheres of OBD spoils than natural forest soils. Moreover, number of AMF spore types decreased due to mining and thereafter, increased with the age of OBDs. Spores of Glomus sp. were found to dominate in the sites. The diversity of AMF in natural forest soil was higher than that of the OBD spoils. About nine types of AMF spores were detected in the NF soils, but only 5-7 types were detected in OBD spoils. The genera AMF detected in different natural forest sites and overburden dumps were Glomus sp, Entrophospora sp, Gigaspora sp, Scutellospora sp, Acaulospora sp, Sclerosystis sp and two unidentified AMF (Type-Margherita).