Results of this experiment indicate that Cassia occidentalis is a toxic plant capable of producing significant losses in cattle. The toxicologic syndrome in the acute form was characterized by sudden onset, recumbency, dark urine, and extensive myodegeneration. A chronic form of the condition may prove to be more important for livestock production, especially in areas where cattle have free access to the plant. Certain enzymic changes were marked a day or two before death. Hematologic changes were insignificant until 12 hours before death. Myopathic lesions in the hindlimbs were found consistently at necropsy.