A reliable technique has been developed for inoculating loblolly pine (Pinus taeda) and slash pine (P. elliottii var. elliottii) seedlings with Fomes annosus under aseptic conditions. Experiments during 2½ years revealed no differences in ultimate mortality due to light, aeration, nutrient substrate, moisture content or pH of substrate, nitrogen source/thiamine levels, seedling age, or isolate variation including host, geographical origin, and antibiotic (fomannosin) or cellulase production. Seedlings died more rapidly in some treatments than in others. One noncellulase-producing isolate killed seedlings more slowly than other cellulase and noncellulase producers. Forest Sci. 16:280-286.