Brachial plexus injuries are uncommon. They are, however, complicated lesions because of the concomitant injury to adjacent structures and the imposing anatomy of the brachial plexus. Physicians who will be consulted in the management of such injuries should periodically consider the principles of management. Diagnosis of these injuries is based on clinical examination, myelography, axon reflex testing, and electrophysiologic studies. The lesion may be open or closed and supraclavicular or infraclavicular. It may be in continuity or there may be nerve disruption or root avulsion from the spinal cord. The anatomic relationships of the brachial plexus are reviewed, the pathophysiology of direct trauma, secondary trauma, and iatrogenic trauma is discussed, and the treatment of the various types of traumatic brachial palsy is surveyed.