Pinusbanksiana Lamb, seedlings were inoculated with nine mycorrhizal fungi and outplanted on an oil-sands containment dyke that had been amended with muskeg peat. After one growing season, E-strain (Complexipes), Hebeloma sp., Thelephoraterrestris Ehrh.:Fr., and Laccariaproximo Boudier each formed mycorrhizae with greater than 40% of the new short roots within 10 cm of the stem. Cenococcumgeophilum Fr., Pisolithustinctorius (Pers.) Coker & Couch, Astraeushygrometricus (Pers.) Morgan, Lactariusparadoxus Beardslee & Burlingham, and Sphaerosporellabrunnea (Alb. & Schw.:Fr.) Svrcek & Kubika each formed mycorrhizae with less than 6% of the short roots on egressed laterals. Of the introduced fungi, only E-strain was present in substantial quantities after 3 years. The quantity of short roots converted to mycorrhizae by indigenous fungi was 4, 33, and 72% after 1, 2, and 3 years, respectively. The change in mycorrhizal fungi appeared to be a noncompetitive replacement process, in which the original short root resident fungus died in the near absence of mycorrhizal fungi. At the end of the 3rd year, the major indigenous fungi converting short roots to mycorrhizae were E-strain, Tuber sp., Suillus-like spp., Myceliumradicisatrovirens Melin, and an unidentified basidiomycete. Inoculation with E-strain and Thelephoraterrestris resulted in a 2- to 3-fold increase in shoot weight after 2 years compared with uninoculated seedlings.