The authors examined the differences between 30 patients with familial schizophrenia (those with a schizophrenic first-degree relative) and 83 patients with sporadic schizophrenia (those with a negative family history for schizophrenia). Although the two groups showed no difference in the intensity of 1) flattened, depressed, or elevated affect, 2) auditory hallucinations, and 3) delusions, more of the familial (56.7%) than the sporadic (18.1%) schizophrenic patients had severe thought disorders. EEGs were performed while the patients were taking neuroleptics; 72.3% of the sporadic schizophrenic patients and 43.3% of the familial patients had an abnormal tracing. The authors conclude that the division of schizophrenia into familial and sporadic forms may represents a valid subclassification.