The incidence ofAspergillus terreus recovered fromAcremonium coenophialum-infected and non-infected tall fescue grass and from the rumens of heifers grazing on the grasses was determined. The recovery ofA. terreus fromA. coenophialum-infected grass was similar to that from non-infected grass. The same was true of the recovery from the rumens of heifers on infected and non-infected grass. All heifers grazing onA. coenophialum-infected grass showed symptoms of the summer syndrome manifestation of fescue toxicosis while those grazing on non-infected grass did not;A. terreus is not a factor in fescue toxicosis in cattle.