The author reports the case of a 47-year-old man who developed an acute polyneuritis in the course of the chronic Chagas'disease. Neurological examination on admission forty-five days after onset showed total ptosis of the left eyelid without internal and external ophthalmoplegia. There was moderate diffuse weakness in the limbs. Tendon reflexes were depressed. Plantar responses were normal. The cerebrospinal fluid cell count and protein level were raised. The relationship between chronic Chagas'disease and peripheral polyneuritis is discussed.