Weather conditions in northern Illinois favored infection of pasture grasses with Claviceps purpurea. A herd of 52 Holstein heifers selectively grazed the seedheads of an orchard grassbromegrass pasture infected with C purpurea and were poisoned. Peptide alkaloids were found in the sclerotia. Clinical signs of intoxication included lameness, edema of the hind limbs, epilation, areas of skin necrosis, and diarrhea. Pathologic findings included myopachynsis of arterioles in the deep dermal areas, lungs, kidney, spleen, submucosa of small intestines and cerebral cortex, focal cracks on the hoofs, and multifocal areas of detachment of the hoof wall. Of the 52 heifers, 3 died on the farm, 1 was euthanatized, and 3 were sold. The remaining heifers conceived without difficulty, and subsequent calvings were uncomplicated.