The purpose of this study was to investigate the abnormality of premovement facilitation in patients with Parkinson's disease. Seven patients with Parkinson's disease and seven healthy subjects participated in this study. The subjects attempted abduction of the index finger in response to a visual start cue, and motor-evoked potentials were recorded from the first dorsal interosseous muscle before movement onset. The rate of premovement facilitation in patients with Parkinson's disease was slower than that in healthy subjects. Additionally, the rate of premovement facilitation as a function of delay from the start cue was positively correlated with the reaction time. These findings indicate that premovement facilitation is abnormal in patients with Parkinson's disease. This abnormality may be partially related to akinesia.