A lot of 150 brains were studied and some anatomical aspects were found peculiar to epilepsy. Macroscopically in most of the cases a crossed cerebrum-cerebellar assimetry was observed. The frontal and temporal lobes, sometimes only the latter ones, were assimetrical, considering the major and the minor hemispheres. The skulls were, sometimes, equally assimetrical. Unilateral changes were noted in Ammon's horn (hypoplasia and sclerosis) of the smaller hemisphere, accompanied by less development of the fimbria, mamillary bodies, the mamillo-thalamic tract, thalamus (chiefly the anterior nucleus) in the same side. Cirsoid aneurysms and dilatation of the septum pellucidum cavity were frequent. These findings are consequent of impairment in cerebral development and are responsible for epilepsy. Hypoplasia and gliosis of the Amnion's horn is a data of the general abiotrophic involvement of one hemisphere or part of it. The author states that in epilepsy there is an anatomical and funtional imbalance of the hemispheres or part of them, which predominates in the rhinencephalic structures. The epileptic seizure may be explained by palliocortical discharge from Amnion's horn or from the archi-encephalic nuclei related to it, with neocortex inhibition and liberation of older structures.