Local field potentials (LFPs) recorded from deep brain stimulation electrodes implanted in the globus pallidus internus (GPi) of patients with hyperkinetic movement disorders (dystonia and Tourette's syndrome) have shown desynchronized activity at 8–20 Hz and synchronized activity at 30–90 Hz during voluntary movements. However, the impact of the speed of the motor task on these frequency shifts is still unclear. In the current study, we recorded LFPs bilaterally from the GPi in seven patients with hyperkinetic movement disorders during normal/slow and fast horizontal line drawing movements as well as during rest. In comparison with rest, the low beta band showed a significant decrease in power during the motor tasks. Low beta power was more suppressed with increasing speed of the movement on the contralateral side. In contrast, a significant increase in power was induced by movements in the high beta and gamma bands on the contralateral side. When comparing slow and fast movements, the power of the low gamma frequency band was significantly elevated on the contralateral side with fast movements. In conclusion, an increase in movement speed changes the power of GPi oscillations by means of a reduction of the activity in the low beta band and an elevation of activity in the gamma band. The current study yields new insights into the physiological mechanism of GPi during the execution of the motor task at low and high speed.