The brachial plexus and its associated structures demonstrate a propensity for certain disease processes not common to other areas of the nervous system. Brachial plexus disease produces a gait disturbance that may mimic musculoskeletal disease. When evaluating a case with possible traumatic brachial plexus disease, one relies heavily on historical, physical, and neurologic information when differentiating musculoskeletal disorders, although both may sometimes be present simultaneously in the same limb. With inflammatory disease, electromyography is extremely helpful, although an empiric dietary change may help confirm a suspicion. Brachial plexus surgery requires careful planning and meticulous technique. Attempts to remove malignant schwannomas have not been as successful as one would hope (Table 2). To a large extent, these dogs are treated late in the course of their disease because they are often treated for extended periods of time for musculoskeletal disease first. Early diagnosis and prompt surgical intervention would help many of these dogs. New histopathologic techniques, electrodiagnostic equipment, and radiographic techniques are helping to define peripheral nerve disease in the companion animal. These techniques will help us categorize and treat these diseases with greater success in the future.