Deep brain stimulation (DBS) is used for advanced and medically intractable patients with Parkinson's disease (PD), essential tremor (ET), and dystonia who meet strict criteria after a detailed motor, cognitive, and psychiatric evaluation. The potential targets are the ventral intermediate nucleus (VIM) of the thalamus for tremor, the globus pallidus interna (GPI) and the subthalamic nucleus (STN) for PD, and GPI for dystonia. The optimal target for PD has not been determined yet, although STN DBS has been performed more frequently in recent years. The mechanism of DBS effect is believed to be associated with disruption of pathological network activity in the cortico-basal ganglia-thalamic circuits by affecting the firing rates and bursting patterns of neurons and synchronized oscillatory activity of neuronal networks. Good candidates should be free of dementia, major psychiatric disorders, structural brain lesions, and important general medical problems. Although the risk for complications with DBS is less than with lesioning techniques, there is still a small risk for major complications associated with surgery. Bilateral procedures are more likely to cause problems with speech, cognition, and gait.