The neurophysiological approach to patients with disorders of consciousness allows recording of both central and peripheral nervous system electrical activities and provides a functional assessment. Data obtained using this approach can supplement information from clinical neurological examination, but also from the use of morphological neuroimaging techniques: computed tomography and magnetic resonance imaging. Neuro-physiological techniques, such as electroencephalography (EEG), evoked potentials, transcranial magnetic stimulation, and EEG in association with functional magnetic resonance imaging, allow monitoring of clinical conditions and can help in the formulation of a prognosis. The aim of this review is to describe the main neurophysiological techniques used in disorders of consciousness to evaluate residual cerebral function, to provide information on the neuronal dysfunction for outcome evaluation, and to differentiate clinically between the vegetative and minimally conscious states.