The following report is an evaluation of the performances of 35 schizophrenic patients and 35 of their siblings on the Wisconsin Card Sorting Test (WCST), a neuropsychological test considered sensitive to frontal lobe functioning. Thirty five normal subjects matched for age and education were the comparison group. The purpose of this study was to examine the relationship of the neurofunctional basis for schizophrenia to its familiar occurrence. Non-schizophrenic siblings of schizophrenic patients did not perform significantly different from normal subjects on the WCST; however, schizophrenic patients performed significantly worse than both their siblings and normal subjects. These results indicate that WCST dysfunction seems to be a characteristic related to the presence of the disease and that non-genetic factors could contribute to the WCST pathological profile.