In visual backward masking, a target is followed by a mask which impedes perception of the target. Masking is much stronger in schizophrenic patients compared to controls. Visual masking is a potential endophenotype of schizophrenia reflecting the genetic underpinnings of the disease rather than the state of the disease. For example, the unaffected relatives of patients show also masking deficits when compared to controls. Here, we investigated the electrophysiological correlates of visual masking by means of high density EEG. We recorded from 192 electrodes and determined stable scalp topologies of evoked activity. Patients showed clearly different EEG patterns. Particularly, controls and relatives showed stronger evoked responses than patients at around 200ms after target onset. We localized these differences to left infero-temporal cortex and relate this abnormal activity to deficits in perceptual organization.