In order to evaluate the possibility of compression of axillar artery by medial and lateral fascicle of brachial plexus, authors performed 26 axillar dissections on cadavers. Second part included analysis of 24 selective angiograms of axillar artery of patients with diagnosis of TOS. Third part included the use of modified hyperabduction test for determination of vascular bruit as safe test for diagnosis of axillar compression. Macroscopic changes of axillar artery by compression of medial and lateral fascicle of brachial plexus were present in 11.5%. Specific angiographic horizontal spike-shaped stop of contrast behind the surgical neck of humerus was present in 12.5%. Use of modified hyperabduction test revealed vascular bruit 29.5%. Specific relation of axillar artery and medial and lateral fascicle of brachial plexus revealed another possible etiologic factor in hyperabduction syndrome as a part of TOS. Use of modified hyperabduction test revealed subclinical phase of possible syndrome.