Pinus rigida × P. taeda seedlings in a nursery was inoculated with basidiospores of Pisolithus tinctorius (Pt) either collected from Suweon, Korea or introduced from U.S.A. to compare the effectiveness of the spores from two different origins as mycorrhizal inocula. Nursery beds were fumigated with methyl bromide and lg of spores was used to inoculate 1㎡ of soil surface just before seed sowing. Seedlings inoculated with American Pt (#250 strain from Georgia, U.S.A.) were 15% taller than Korean Pt at the end of the first growing season. The seedlings from fumigation treatment only (no inoculation involved) was slightly taller (statistically unsignificant) than those with Korean Pt, but slightly smaller than those with American Pt. In a subsequent year experiment, the seedlings inoculated with American and Korean Pt after soil fumigation were 66% and 60% taller, respectively, than seedlings infected by natural fungi without soil fumigation, suggesting the dual effects of Pt and fumigation on the seedling growth. Therefore potential of Pt spores for an effective inoculum exists and selection of Pt strains which have adapted to specific local environments is needed to develop better sources of mycorrhizal inocula.