Clinical and neurophysiological findings for 28 patients (mean age 15 years) with mental retardation, autism, and epilepsy were described, including classification of seizure type and epileptic syndrome, etiology, severity of autism and epilepsy, electroencephalography findings, and neuroimaging findings. No particular epileptic syndrome correlated more frequently with autism, and autism severity was not correlated with tendency to develop seizures. (Author/DB)