Microdysgenesis is a subtle malformation, which is often found in specimens from epilepsy surgery. It is, however, not clear whether the changes are focal or diffuse. A recent autopsy case offered an opportunity to investigate whether microdysgenesis found after temporal lobe surgery was focal or widespread in the brain. The entire brain of a 20-year-old patient who died suddenly and unexpectedly was examined histologically. Microdysgenesis had previously been diagnosed after a left temporal lobectomy performed because of therapy-resistant seizures. A light microscopic examination was performed on specimens stained with Luxol-fast blue-cresyl violet and polyclonal antibodies to glial fibrillary acidic protein. Widespread microdysgenesis with irregular nerve cell distribution in the cortex and an increased number of nerve cells in cortical layer I and in the white matter was found in the right temporal and parietal lobes and bilaterally in the frontal and occipital lobes. The post-mortem examination confirmed the previous diagnosis of microdysgenesis and showed that the changes were widespread in a patient who was operated on because of focal epilepsy.