The etiology of developmental stuttering is still unknown. In some patients, stuttering re-emerges or is aggravated with the onset of Parkinson's disease (PD). We here report on a patient with PD treated by deep brain stimulation of the subthalamic nucleus and severe deterioration of stuttering under effective stimulation. Positron emission tomography (PET) of regional cerebral blood flow (rCBF) in stimulation on- and off-conditions showed overactivation of cerebral and cerebellar motor systems during speech activation and was in line with recent PET studies investigating brain activation during stuttering. The abnormal rCBF pattern increased in the stimulation on-condition and was associated with a marked worsening of stuttering. Clinical and imaging findings in this patient support the hypothesis that the basal ganglia circuitry plays an important role in the pathophysiology of stuttering.