The elusive diagnosis of thoracic outlet syndrome and its controversial relationship with carpal tunnel syndrome is examined by a retrospective study of 1000 cases of carpal tunnel syndrome and 63 cases of thoracic outlet syndrome. Thoracic outlet syndrome is rare and difficult to accurately diagnose. The signs and symptoms of thoracic outlet syndrome lack specificity. The ancillary tests used to evaluate patients with expected thoracic outlet compression also add little objectivity to the diagnostic process. Carpal tunnel syndrome is still as inaccurately diagnosed as thoracic outlet syndrome. Carpal tunnel syndrome can easily be confused with thoracic outlet syndrome when it presents with shoulder pain. The spontaneous occurrence of these two syndromes in a single patient is extremely rare. The relationship of carpal tunnel and thoracic syndromes does not represent an example of the double crush syndrome. In this study, the incidence of combined carpal tunnel and thoracic outlet syndromes approached zero. Surgical treatment of the carpal tunnel syndrome alleviated pain from the upper extremity in the majority of patients.