The aim of the study was to discriminate the auditory event-related potentials (ERP) abnormalities in the P300 paradigm as the possible neurophysiological endophenotypes (pathogenetic predisposition markers) of schizophrenia. Deviations of the parameters of different waves of auditory ERP were determined in a sample of patients as compared to the controls, the influence of patient's clinical state (measured by PANSS) upon ERP abnormalities was studied. The comparison of neurophysiological characteristics was carried out also in mentally healthy parents from the families with so-called "sporadic" cases of schizophrenia and in parents from the families, in which the other spouse was either affected with mental disorder or had relatives with schizophrenia. The data obtained suggest that two neurophysiological abnormalities of auditory ERP - the decrease of N100 amplitude in ERP to non-target stimuli and reduction of P300 amplitude, fulfill the "endophenotype" criteria.