Fifteen range cows died of oxalate poisoning caused by ingestion of Rumex venosus. Ecchymotic and petechial hemorrhages were prominent on the abdominal serosal surfaces. Approximately 2 L of thin, yellowish fluid was in the abdominal cavity, and mesenteric lymph nodes were enlarged and edematous. Other findings included catarrhal abomasitis; enteritis; pale, edematous kidneys; congested lungs; fatty infiltration of the liver; and nephrosis. In the kidneys, birefringent crystals resembling oxalate crystals were demonstrable only when frozen sections were examined.