Thoracic outlet syndrome refers to compression of the subclavian vessels and brachial plexus at the superior aperture of the thorax. it was previously designated according to presumable etiologies such as scalenus anticus, costoclavicular, hyperabduction, cervical rib and first thoracic rib syndromes. We experienced a case of thoracic outlet syndrome[costoclavicular syndrome] which was caused by posttraumatic left clavicular fracture. Patient had suffered from swelling and cyanosis of left forearm and hand. preoperative vascular doppler test, angiography and venography were performed. First rib resection was done with transaxillary approach. After operation preoperative cyanosis and swelling of left forearm and hand were disappeared. Postoperative course was uneventful.