The thoracic outlet syndromes of the upper extremities consist of many disorders. The most important two are the costoclavicular syndrome (compression of neurovascular structures between the clavicle and the first rib) and the scalenus anticus syndrome (compression of these structures within the scalene triangle). Congenital abnormalities of the clavicle, congenital small thoracic outlet, high first rib, cervical ribs of all configurations, pectoralis minor and pectoralis major syndromes, and others may occur. The costoclavicular syndrome and scalenus anticus syndrome have been considered the most prevalent compression syndromes and are amenable to surgical or medical treatment. Quantitative measurements of the microcirculation of the fingertip were examined with the shoulders and head in various positions to provide quantitative information relative to the costoclavicular and scalenus anticus syndromes. A laser instrument was ideal for this purpose, for results were quantitative and no counterpressure was applied during the measurement. The technic applied was highly successful in separating quantitatively the normal individuals from those with either costoclavicular syndrome or scalenus anticus syndrome.