Brain tissue from six autistic mentally challenged individuals was studied as part of a neuropathological investigation of autism. In cases where the parents had not been seen prior to the patient's passing, diagnostic interviews using standardised questions were done. Areas of cortical abnormalities were found in four of the six brains, four of which were megalencephalic. The brainstem, especially the inferior olives, had developmental anomalies as well. In all of the adult instances, there was a decrease in the number of purkinje cells, which was occasionally accompanied by gliosis. The results refute earlier assertions of localised neurodevelopmental problems. They do indicate that the cerebral cortex is probably involved in autism.