Investigations using event-related potentials (ERPs) in brain-injured patients affected by neuropsychological disorders of perception, attention, memory, and language, and other special syndromes such as blind-sight, neglect, prosopagnosia, and apraxia are reviewed. These electrophysiological techniques can be used to assess the integrity of specific brain processes during the performance of cognitive tasks in which behavioral impairments are observed. A special feature of ERP technique is that it reveals ongoing and covert processing which may not be fully assessed by measuring only overt behavioral performance.