A double-blind sham-controlled study demonstrated that high-frequency repetitive transcranial magnetic stimulation (rTMS) over the supplementary motor area (SMA) provided relief of motor symptoms in patients with Parkinson's disease (PD). However, it remains to be determined which parkinsonian symptoms were improved by this treatment. Subanalysis of Unified Parkinson Disease Rating Scale revealed that rTMS over SMA significantly improved bradykinesia in PD. Results support the hypothesis that neuronal activity of SMA was profoundly associated with hypokinetic symptoms in PD.