Thirty five mentally retarded girls, with epilepsy associated with behavioral troubles, were treated with carbamazepine in a medicopedagogic institution for 4 months to 7 years. Fifty percent got better, thirty percent showed a disappearance of the epileptic spells and 67% showed an aggravation of the EEG. Improvement of behavior and absence of spells are more frequent in primary generalized epilepsy as in secondary generalized epilepsy and even less frequent in secondary generalized epilepsy. Results are better in epileptics only showing tonicoclonic crises than in those with absences. They are also better in dementia epileptica than in epilepsy without dementia. The aggravation of EEG, consistent with the disappearance of epileptic crises and behavioral improvement, is most often observed in patients with epileptic absences or progressive dementia.