INTRODUCTION: Muscle vibration (MV) influences the perception of movement and proprioception especially without visual control. In idiopathic Parkinson's disease, MV has a smaller impact on kinaesthesia than in healthy people; this impact may be enhanced by dopaminergic medication. This peculiarity is deemed to contribute to the genesis of hypometria and bradykinesia. The exact mechanisms of the reduced influence of MV on kinaesthesia in IPD are unclear. METHODS: The processing of proprioceptive stimulation of forearm muscles was examined in 10 IPD patients in the off and on state using transcranial magnetic stimulation (TMS) and compared to that of 10 age-matched controls. A paired-pulse paradigm to investigate intracortical excitability was used to record motor evoked potentials (MEP) in the extensor and flexor carpi radialis muscles (ECR and FCR) of the more impaired arm without and during proprioceptive stimulation − 80 Hz muscle vibration (MV) of the belly of the ECR. RESULTS: In contrast to controls, MV does not facilitate MEPs in IPD in the off state. In the on state MV causes, like in controls, a selective facilitation of MEPs recorded from the vibrated muscle. This effect is considerably smaller in IPD, though. CONCLUSION: The processing of vibratory input in IPD is disturbed and can be partially normalized by levodopa. This effect can be detected by means of TMS.