Sudden increase in mortality was observed in 2 different flocks of mature breeder geese fed green onions. At necropsy, birds had pale epicardium with random petechiation, sanguinous fluid accumulation in the pericardial sac, and mild swelling of the liver and spleen. Histologically, there was accumulation of hemosiderin in hepatocytes, Kupffer cells of the liver, macrophages, and renal tubules. There was also moderate to severe hepatic necrosis, vacuolation of hepatocytes, splenitis, and renal tubular nephrosis. To assess the effects of green onion ingestion, 2 feeding trials were carried out in 3 mature White Chinese geese. In the first trial, onions were thoroughly mixed with pellet maintenance ration. In the second trial, onions were offered in a separate trough from the pelleted diet. During the 21 days of experiments, the red blood cell count and hematocrit decreased, whereas the polychromasia and reticulocyte estimate increased. The blood changes were more marked in birds from the second feeding trial. Gross and histologic changes were similar in both trials. Mild swelling and severe darkening of the liver were the only significant findings at necropsy. Histologically, the liver looked similar to that seen from the field outbreak. The liver contained moderate amounts of hemosiderin in the hepatocytes and Kupffer cells, and had centrolobular necrosis and vacuolation of hepatocytes. This experimental study demonstrated that anemia and liver pathology could be caused by ingestion of onions. Furthermore, Heinz bodies are not a consistent finding in the blood of geese fed onions.