Epileptic seizures are frequently reported (4-32%) in autism. These values are higher than in the normal population of children and adolescents (0.5%). In the literature there is no uniform description of epilepsy in autism. We examined 106 patients with autistic disorder divided into three groups on the basis of presence or absence of EEG paroxysmal abnormalities (PA) and / or epilepsy including febrile convulsions (FG). Our patients presented an autistic syndrome unrelated to clear congenital or acquired encephalopathy. The prevalence of epilepsy and EEG PA was 23.6% and 18.9%, respectively. Significant differences between the three groups appeared for (i) familial antecedents for epilepsy / FC and neurologic and psychiatric diseases (P < 0.004), (ii) a different proportion between the three groups for mental retardation (P < 0.03), (iii) and EEG fast activity (P < 0.04). Our patients showed several types of epilepsy, including idiopathic forms with seizure onset after the age of 10 in 45% of cases. Seizures were mainly partial, not frequent and controllable by anti-epileptic drugs. PA were mostly focal and multifocal and in 45% of cases were typical of benign childhood partial epilepsy with centro-temporal spikes. The higher incidence of epilepsy and EEG PA is apparently not related to organic pre-, peri- and postnatal antecedents or cerebral lesions. On the contrary, genetic factors responsible for autism and epilepsy seem important in the genesis of these two disorders.