Cattle and sheep, grazed successively on the same pasture and given the same supplementary feeding, developed ataxia and several animals became recumbent. Three cattle died within two weeks and the worst affected sheep were killed for laboratory examination. The supplementary diet which consisted largely of a distillery by-product, malt culms, was submitted for mycological examination and fed to two housed lambs. Aspergillus clavatus was cultured from the culms, and both the affected sheep and the housed lambs showed cerebrospinal degenerative changes. The clinical signs and neuropathology were closely similar to a mycotoxicosis, attributed to A clavatus, which is seen infrequently in cattle in France, Bulgaria, South Africa and China.