Chronic deep brain stimulation (DBS) has been a rapidly evolving area of neurotherapeutics since its initial introduction for the treatment of Parkinson's disease and essential tremor in the 1990s. For these conditions, DBS is now considered accepted therapy for patients failing to adequately respond to m- ical treatment. Since the 1990s, new clinical indications, anatomic targets, and technologies have contributed to an expanding role for DBS in the treatment of other movement disorders such as dystonia and Tourette syndrome as well as for other neurologic disorders such as epilepsy and cluster headache. Early experience has also been reported for psychiatric syndromes, such as obs- sive–compulsive disorder and depression. Experience with DBS in psychiatric disorders is very limited but is reviewed in this volume as neuropsychiatric indications are expected to grow in coming years. Because of the rapidly increasing application of DBS for neurologic and psychiatric indications and the recruitment of increasing numbers of neu- logic, neurosurgical, and psychiatric clinicians to the field, it is appropriate to provide a resource that updates the underlying scientific background, describes methodologies and standards of treatment, and provides information on new technologies essential for clinical success and to advance the field. Deep Brain Stimulation in Neurological and Psychiatric Disorders begins with reviews of the functional anatomy and physiology of motor and nonmotor aspects of the basal ganglia and their connections, which underlie the application of DBS to neurological and psychiatric disorders.