Thoracic outlet syndrome (TOS) is the term commonly used to describe patients with symptoms attributed to compression of the brachial plexus and subclavian vein and artery in the region of the thoracic inlet/outlet. TOS remains extremely controversial with respect to its existence, diagnosis, conservative management, and surgical treatment. The diagnosis is based upon clinical evaluation, reproduction of patient symptoms with arm elevation, and the absence of other relevant pathology. Conservative management should be directed towards correction of postural abnormalities and muscle imbalance in the cervicoscapular region. Patient education compliance to a home exercise program and behavioral modification at home, work, and sleep is necessary for a successful outcome. Surgical decompression of the brachial plexus is best achieved through a supraclavicular approach and should be reserved for the few patients in which conservative management has failed to improve symptoms.