IN a recent communication, Percival and Thornton1 referred to the relationship between fungal spores and a test for hepatotoxic grass. It has since been shown that the fungus is Sporidesmium bakeri Syd. and is the source of the hepatotoxin which causes the specific liver damage which occurs in the disease known as ‘facial eczema’. In connexion with this work, we have isolated a strain of B. subtilis which has a marked inhibitory effect on the growth of this fungus on culture media. Further investigations are being carried out to determine its spectrum of antibiotic activity and its relationship to the fungus in the field.