A study of visual evoked potentials (VEP) was carried out on a group of 30 patients (8 males and 22 females) with a DSM-III-R diagnosis of schizophrenia: disorganized (5 cases), paranoid (12), residual (6), or undifferentiated schizophrenia (6 cases). During the study 20 patients were treated with neuroleptics, while 10 patients received no psychotropic medication. A control group consisted of 50 healthy persons (25 males and 25 females). A full chessboard stimulation was applied. Differences between evoked potentials from electrodes located on the top of the head and in EEG points O1 and O2 were registered. Symmetry of registered VEPs and their amplitudes were assessed and compared with these obtained from healthy controls. Differences in mean amplitudes of P1, P100 and N2 were found. The mean amplitudes o Pl and N2 were higher in the group of schizophrenic patients, while the mean Pl00 amplitude was higher in the control group. The amplitude differences were symmetrical and pertained both to left-and right-sided VEPs. As regards N1 and P300 amplitudes, the differences in their distribution were statistically insignificant. Standard deviations of amplitudes in the group of schizophrenic patients were much higher than these in the control group, which indicates a much more marked inter-individual VEP variability in patients diagnosed with schizophrenia.