Neurography of the brachial plexus was carried out in 180 patients with suspected thoracic outlet syndrome and in 30 normal subjects. In the thoracic outlet syndrome, abnormalities were found in 85% of suspected cases. Narrowing was seen in the scalenus triangle (30%), in the costoclavicular-space (75%) and at the subcoracoid level (6%). Translucent lines were present in 53%, and in 28% of the controls. After successful operation, the appearances returned to normal. Neurography was helpful in making the diagnosis and in determining the correct surgical procedure.