The extent of electroencephalographic (EEG) abnormalities in 23 consecutive patients with unilateral neglect was compared with the extent of EEG abnormalities in 20 matched aphasic controls. In the neglect group, 22 patients showed EEG slowing that extended over the entire hemisphere. In the control group only 8 patients showed similar hemispheric slowing. This study demonstrates that patients with unilateral neglect from discrete lesions may have EEG slowing in regions of the hemisphere that are remote from the lesion. This study also provides support for the hypothesis that neglect is a unilateral arousal defect.