Failed back surgery syndrome is a common problem with enormous costs to patients, insurers, and society. The etiology of failed back surgery can be poor patient selection, incorrect diagnosis, suboptimal selection of surgery, poor technique, failure to achieve surgical goals, and/or recurrent pathology. Successful intervention in this difficult patient population requires a detailed history, precise physical examination, and carefully chosen diagnostic tests. The diagnostic evaluation should endeavor to accurately identify symptoms, rule out extraspinal causes, identify a specific spinal etiology, and assess the psychological state of the patient. Only after these factors have been assessed can further treatment be planned.