Deep brain stimulation (DBS) at the subthalamic nucleus has been approved as an effective treatment for refractory symptoms of Parkinson's disease (PD). Studies have shown that bilateral DBS surgery in PD patients results in clinical improvement without reducing dopamine transporter function. Here, we report our longitudinal findings in one PD patient, ie, decreases in striatal dopamine transporter binding during one year of follow-up after unilateral DBS at the subthalamic nucleus. Based on this case, we hypothesize that clinical benefit after unilateral DBS may be not directly associated with changes in function at the subthalamic nucleus.