Introduction: The coexistence of epilepsy in patients with autism spectrum disorder (ASD) is a 30% and an electroencephalographic alteration reaches up to 90% according to series described. The implication that these alterations occur in language development, intellectual coefficient and the final prognosis is a matter of discussion.

Objective: To describe the electroencephalographic characteristics of patients with ASD monitored in the child neurology service.

Materials and Methods: A cohort study. Descriptive analysis of 59 patients admitted record to polyclinic pervasive developmental disorder, divided into 3 groups (Classic autistic disorder, Pervasive nonspecific and Asperger syndrome).

Results: n = 59 (boys n=52). Mean age 8.3 years (range 3-15). Clinical epilepsy in 3 patients. 41% abnormal EEG. Classic autistic patients 9/21 had abnormal EEG (generalized n=2, focal n=3, slow n=2, pharmacological n=2), 2/9 have epilepsy. In the pervasive nonspecific group, 13/31 had abnormal EEG (generalized n=1, focal n=9, slow n=2, pharmacological n=1), 7 anticonvulsant treatment them all with focal EEG. In all treated patients showed abnormal development of language. In Asperger syndrome group 5/7 with normal EEG, 2/7 with generalized abnormal EEG without current treatment.

Conclusion: Our series is similar to that described in the literature, with 41% of EEG abnormality. The decision of use antiepileptic drugs was based on the location of the electric bulb (frontal and/ or temporal) and its implication from theory in language development. However we cannot conclude if their response was only by drug treatment or as part of their evolution.