Abstract:Event‐related potentials were recorded in 54 schizophrenics and 88 age‐matched controls during a two‐tone discrimination (odd ball) task. All the subjects were free from medication. In the schizophrenics, the mean amplitudes of the N100, P300 and Slow Wave latency ranges were decreased, and the amplitude of the P200 latency range was greater than that for the controls. These reductions and the increase were found both for the ERPs elicited by rare target stimuli and for those elicited by frequent nontarget stimuli. The peak latency of N200 to rare stimuli was more prolonged in the schizophrenics than in the controls. This finding confirms the prolongation of N200 latency that Brecheret al.(1987) found for a different visual stimuli task. Neither the N100 nor P300 latency differed between the two g