Movement-related cortical potentials (MRCPs), especially the premovement components seen only in association with voluntary movements, may represent the higher brain functions related to preparation for voluntary movements. Recent advances in many aspects (single unit and field potential recordings in animals, intracranial recording of MRCPs in epileptic patients, magnetoencephalography, and positron emission tomography) have provided new information about the physiological significance of MRCPs. In contrast to the findings on scalp recordings, in which the early potentials prior to movement onset are seen more widely, the main cortical generators appear to be discretely localized in bilateral primary and supplementary motor areas with a contralateral predominance. This review outlines the findings in scalp-recorded MRCPs and compares them with the results of invasive recordings, paying special attention to their physiological significance.