This study evaluated the effectiveness of a supraclavicular brachial plexus neurolysis, without a first rib resection, in relieving the symptom complex traditionally termed "thoracic outlet syndrome." The hypothesis to be tested was that patients with a history of trauma may sustain stretch-type injury and subsequent scarring in and about the brachial plexus which is left untreated during transaxillary first rib resection. This prospective study included 14 patients who each had a neurolysis of the five roots and three trunks of the brachial plexus, plus an anterior scalenectomy through a supraclavicular approach. The results were determined on 11 patients with a mean follow-up of 26.4 months. The results of surgery were five excellent (45 percent), five good (45 percent) and one who failed to improve (10 percent). It is concluded that, with a history of trauma, the symptom complex commonly referred to as "thoracic outlet syndrome" may be primarily due to entrapment of the brachial plexus at sites proximal to the interval between the first rib and the clavicle. It is suggested that: 1) the term "brachial plexus compression" best describes the syndrome without directing the surgeon to remove any one specific anatomic structure and 2) the supraclavicular approach permits excellent surgical exposure of the compressed neurovascular structures. An unexpected observation was the formation of the lower trunk from C8 and T1 proximal to the first rib in the majority of these patients.