In the greenhouse, subcrown internodes of wheat plants were inoculated withCochliobolus sativus(Ito & Kurib.) Drechsler ex Dastur,Fusarium culmorum(W. G. Smith) Sacc.,F. acuminatumEll. & Ev., orF. sulplureumSchlecht. and at various times subsequently withC. sativus; or the internodes were inoculated withC. sativusand subsequently with it or aFusariumsp. Using isolation of the fungi as the criterion for infection, it was found that prepossession of the internode byC. sativusdid not prevent later invasion by it or by the fusaria; however,C. sativuswas a relatively unsuccessful challenger toF. culmorumandF. acuminatum. The results suggest that whenC. sativusand one of these twoFusariumspp. appear together in isolations from common root rot diseased plants that the initial invader wasC. sativus.