Impairments of thought and cognition are among the principal characteristics of schizophrenia. Number of previous studies suggested that P300 evoked potential may serve as an useful diagnostic method for evaluation of patients with presumed cognitive impairment. Therefore, we recorded auditory P300 ('Oddball' paradigm) in 17 medicated schizophrenic patients, and compared them with normal controls. Additionally, clinical characteristics of the patients were quantified by PANSS and BPRS scales and possible correlations between P300 parameters and these scales were tested. The dominant findings were highly significant prolongation of mean P3 latency in group of schizophrenic patients and high percentage (almost 60%) of patients with abnormal prolongation of this latency. The mean latencies of other peaks were also statistically significantly prolonged, but overlapping of individual values between patients and controls was very extensive, and the number of patients with normal latencies was neglectably low. There was no statistically significant difference between patients and control in N1-P2 and N2-P3 amplitudes. Correlation of P300 parameters with clinical parameters revealed tendency toward longer P3 latencies with higher degree of global psychopathology (quantified by BPRS score), as well as tendency toward lower N2-P3 amplitudes with more prominent negative symptomatology (quantified by NSS score). In conclusion, it can be said that for schizophrenic patients P300 evoked potentials represent a promising neurophysiological tool for assessing functional integrity of the CNS structures involved in cognition.