The surgical treatment of chronic epilepsies is increasing rapidly and involves neuropathologists in the care of patients with chronic and medically intractable seizure disorders. Herein we review the histopathologic findings in 279 consecutive surgical specimens of patients with chronic pharmacoresistant epileptic disorders. Aspects that are relevant to the diagnostic surgical pathologist such as the terminology of developmental lesions and Ammon's horn sclerosis are discussed. In 87 cases (31.2%), there were tumors in which all but two were of low histopathological grade (WHO grade I or grade II). The most common tumors were gangliogliomas, pilocytic astrocytomas, oligodendrogliomas, fibrillary astrocytomas and dysembryoplastic neuroepithelial tumors. Among the most frequent non-neoplastic focal lesions, microscopic glioneuronal hamartias, circumscribed vascular malformations, glioneuronal hamartomas and porencephalic defects were most frequent. The hippocampal formation was structurally well preserved in 71 specimens of patients with temporal lobe epilepsy. In 51 of these (71.8%) cases, Ammon's horn sclerosis was present. The findings suggest that the structural lesions observed in the great majority of the specimens are closely related to the pathogenesis of intractable seizures.