Ponderosa pine (Pinusponderosa Dougl. ex Laws.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), Shasta red (Abiesmagnified var. shastensis Lemm.), and white fir (Abiesconcolor (Gord. & Glend.) Lindl. ex Hild.) seedlings were inoculated in a bare root nursery with basidiospores of Pisolithustinctorius (Pers.) Coker & Couch. The spores were applied at three rates with or without cold–wet pretreatment of 7 or 21 days. Pretreatment did not affect spore efficiency as inoculum. Only ponderosa pine responded to inoculation. Inoculations in the greenhouse with a wider range of spore application rates revealed that a higher concentration of spores was needed to induce an increase in growth and mycorrhiza formation of Douglas-fir than ponderosa pine. These levels were much higher than those used in nursery inoculations.