Eighty untreated patients suspected to have leprosy were submitted to neurophysiological examination and later compared with the clinical diagnosis. Among the patients who had leprosy confirmed, 98% had EMG abnormalities. Motor and sensory amplitude reduction was the earliest and the most frequent abnormality. Low conduction velocity of the ulnar nerve across the elbow was present in over 55% ot the patients. A «mosaic» peripheral polyneuropathy was the most characteristic finding, and seems to be helpful to the diagnosis of leprosy. All of the clinical forms showed BMG abnormalities, and even some asymptomatic contacts, however the abnormalities increase from ;he indetermined and tuberculous to the borderline and Virchow's forms.