During the last decade, it has become increasingly clear that DBS represents a useful adjunct for therapies to control various symptoms of Parkinson's disease. The stimulation sites include the thalamic nucleus ventralis intermedius(Vim), globus pallidus internus(GPi) and subthalamic nucleus (STN). The clinical data of DBS therapy currently available from the literature, together with our own experience, are reviewed. The results of our double blinded evaluation of the effects of GPi and STN stimulation are also summarized. DBS therapy affords the best effect on tremor when the Vim is selected as the stimulation site. DBS therapy is also useful for controlling rigidity when the GPi or STN is stimulated. Improvement of bradykinesia may often be induced by DBS therapy involving the GPi or STN. Dopa-induced dyskinesia can be attenuated effectively by the direct and/or indirect effects of DBS therapy. Two advantages of GPi and STN stimulation were identified in our double blinded evaluation. Firstly, the stimulation can supplement a reduced action of levodopa during the off-period. It thus improves the patient's daily activities through attenuation of the motor fluctuations. Secondly, the stimulation can replace part of the action of levodopa during the on-period. It thus attenuates dopa-induced dyskinesia through a reduced dose of medication. More importantly, the stimulation improves the daily activities in dopa-intolerant patients who are being administered a small dose of levodopa because of unbearable side effects. In addition, GPi stimulation has its own inhibitory effect on dopa-induced dyskinesia.