The American chestnut, Castanea dentata, was devastated by an exotic fungal pathogen, Cryphonectria parasitica. Endophytes, organisms that reside within host plant tissue without causing symptoms, may be a reservoir for sources of biocontrol agents active against C. parasitica. Endophytes isolated from chestnut stems have shown antagonism against the blight fungus in in vitro dual-culture experiments and now need tested in living seedlings.