The diagnosis and treatment of thoracic outlet syndrome based on a personal experience with 473 patients resulted in relief of symptoms in over 90 percent of patients treated operatively. The diagnosis centers on a thorough history and the exclusion of other causes of arm and shoulder pain, utilizing a strict flow pattern of differential diagnosis. Angiography and electromyography are of limited value and should only be performed in selected cases. Operation should be reserved for the thoroughly evaluated patient who continues to have pain despite adequate conservative therapy. Transaxillary removal of the first rib, fibromuscular bands, and cervical rib, when present, is the operation of choice.