A series of thirteen patients with paralysis and sensory abnormalities resembling Erb's palsy, occurring in Air Force Academy Cadets, and caused by the abnormal posture called the military brace, has been presented. The syndrome is one of brachial plexus palsy of the fifth cervical nerve or of the sixth cervical nerve, or of both. The cause is thought to be an anomalous relationship between the nerve roots and the anterior scalenus muscle, which allows nerve-root entrapment to occur during contraction of the scalenus muscles.