A comprehensive investigation of nerve motor conduction velocity was carried out in the ulnar nerve of 70 patients in the chronic stage of Chagas disease. It was found that 2.6% of them, had slowness of the large motor axons at distal segments and 14% at proximal segments. Twenty seven percent of them had also slowness of conduction at the smallest motor fibers. These observations signal that some patients in the chronic stage of the infection may develop a motor neuropathy.