OBJECTIVE: The authors examined the relationship between premorbid adjustment in schizophrenia and event-related potential data and neuropsychological data obtained after onset of the illness. METHOD: They interviewed 13 male veterans with chronic schizophrenia, 12 normal comparison subjects, and their first-degree relatives and also obtained objective data from the patients' school records and charts. They used interview and objective data to score the Cannon-Spoor Premorbid Adjustment Scale. Patients and comparison subjects were also given event-related potential tests, the Wisconsin Card Sorting Test, and the Wechsler Memory Scale-Revised. RESULTS: Worse premorbid adjustment in the schizophrenic patients was significantly associated with a marked reduction of the N2 component amplitude of the auditory event-related potential measured over the left temporal and central regions, but it was not associated with the P3 component amplitude. Worse Premorbid Adjustment Scale scores were significantly associated with more perseverative errors on the Wisconsin Card Sorting Test and worse performance on the visual memory span task of the Wechsler Memory Scale. CONCLUSIONS: Premorbid adjustment may predict the severity of specific neurophysiological and neuropsychological abnormalities in schizophrenia.