Deep brain stimulation in both the globus pallidum (GPi) and subthalamic nucleus (STN) has been reported to be effective in control of Parkinsonian symptoms. However, the relative safety and efficacy of long-term GPi versus STN stimulation has not been investigated. The goal of the present study is to determine in a prospective, randomized manner the safety of subthalamic and pallidal stimulation in the control of Parkinsonian dyskinesias, akinesia and rigidity and to examine the efficacy of stimulation at either target in the function outcome of patients with Parkinson's Disease.