Twenty-one schizophrenics and 21 controls were exposed to a tenminute sequence of frequent and infrequent auditory stimuli. The amplitude of the third positive-going component (p3) of the average evoked response to infrequent stimuli was much larger in the control group (P<.0003). Using a P3 amplitude of 3.20渭v in the first 2.5 minutes as a dividing point, only seven of the 42 subjects were misclassified. This amplitude had a significant correlation of -.48 with patient's age at first hospitalization. Amplitude of the second positive-going component (P2) to frequent stimuli was also much larger in the control group (P<.003). This amplitude has a significant correlation of -.41 with medication dosage in terms of equivalent amounts of chlorpromazine. Behavioral scales failed to correlate significantly with evoked response measures. Evoked response latencies did not distinguish the two groups.