A discrete aspen clone was sampled for ectomycorrhizal sporocarps over 4 years in an area impacted by copper mining in Butte, Montana. Locations of sporocarps were noted and species identified. A majority of the mycorrhizal fungi found in the aspen stand were early colonizers or species characteristic of disturbed sites, including Inocybe lacera, Laccaria laccata, Paxillus vernalis, and Tricholoma sclapturatum. Ectomycorrhizal rootlets were sampled to determine if above ground species reflected the abundance and distribution of species below ground. Over 94% of the mycorrhizae were identified to species by morphology and RFLP analysis, and 91% (excluding Cenococcum-type) were species which fruited. One fourth of the mycorrhizae were Paxillus vernalis which produced one sporocarp in 4 years. Fruitings exhibited a clustered “edge effect" at the canopy perimeter, in contrast to their mycorrhizae, which were found throughout the stand. The unusual vertical distribution of mycorrhizae to a depth of 48 cm, with few in the top 16 cm of soil is most likely due to moisture, nutrient, and organic matter considerations. Mycorrhizal members of the Cortinariaceae were an important component of the mycoflora of Populus tremuloides in Montana. Species of the mycorrhizal genus Inocybe, which is not well known in North America, were particularly prevalent in the aspen stands near Butte. Thirteen of the 16 species of Inocybe that occurred with aspen in these areas were in the Cortinatae group, having smooth spores, thick-walled pleurocystidia, and a cortina. Several of the species have previously been reported with aspen in Europe. A majority of the 16 species were linked for the first time to aspen in North America. This is the first report of I. flavella, I. longispora, and I. pseudodestricta from North America. / Ph. D.