Following traumatic retrosternal dislocation of the clavicle, the patient presented with thoracic outlet syndrome 6 months postinjury with swelling and cyanosis of the right upper extremity, and cramps of the right arm and forearm after heavy manual work. When open reduction of the dislocated clavicle failed, the medial half of the clavicle was resected. Four years postoperation, the patient is doing well, and is asymptomatic. A review of the literature, anatomy, mode of injury, mechanism of injury, pathology, clinical picture, diagnosis and treatment are discussed.