Fourteen patients were identified with (1) pain and sensory changes in a brachial plexus distribution, (2) aggravation of pain with use of the affected extremity, and (3) pain on palpation over the brachial plexus. All patients had minimal or no intrinsic hand muscle atrophy. Only one patient had cervical ribs. Nerve conduction studies were normal, and electromyography (EMG) showed mild chronic neuropathic changes in 2 patients. None of the patients responded to conservative therapy over a prolonged period (7-12 months). A compressive brachial plexopathy from abnormally attached or enlarged scalene muscles that affected both upper and lower trunks of the brachial plexus was found at surgery in all patients. In 13 patients, at least one fibrous band compressed the lower trunk of the brachial plexus. Therefore, neurogenic thoracic outlet syndrome can occur from cervical bands and scalene muscle anomalies without intrinsic hand muscle atrophy, cervical ribs, enlarged C7 transverse processes, or EMG abnormalities.