Frontal and vertex CNVs were studied in 8 selected nonschizophrenic patients subjected to unilateral or bilateral extensive prefrontal lobotomy. The dorsomedial thalamo-frontal pathways had been severed and their regeneration must be considered impossible. Standard CNV task (S1-S2-R) was followed in order to elicit CNVs from the frontal areas anterior to the line of sections and at Cz. In 7 out of 8 patients it was quite easy to evoke CNV with almost normal features and equal latencies in each case from all the cortical areas explored. These results show that CNV formation is not grossly altered in the prefrontal areas which have been irreversibly deprived of normal bi-directional mediothalamic-frontocortical connnections. This suggests that the role of the dorsomedial thalamo-frontal pathways are not essential in the genesis of the frontal CNV in humans. These findings would suggest that the CNV is a diffuse electrical event essentially related to a unitary cerebral process mediated fundamentally by nonspecific ascending meso-diencephalic reticular systems. The differences in morphology and polarity of the CNVs detectable in various brain structures are presumably related to their intrinsic anatomo-functional characteristics and to the method commonly utilized in recording the CNV.