Eighty-five cattle (calves and yearlings) were allowed 1000 kg of onions (Allium cepa) a day. Signs of poisoning were observed after five days; 22 animals were affected, one fatally. New illnesses continued to occur for five days after the withdrawal of onions from the diet. Clinical signs included inappetance, tachycardia, staggering and collapse, with jaundiced conjunctivae and haemoglobinuria. Haemolytic anaemia with Heinz bodies in the red cells and leucocytosis were demonstrated.