Two patients with negative spikes in central and temporal regions and positive spikes on the anterior projections were selected out of 36 patients with clinical characteristics associated with the Lennox syndrome. All 36 patients were submitted to clinical therapeutic and electroencephalographic longitudinal follow-ups. The electroencephalographic findings on both patients selected for the present study came from children with beningn functional epileptic syndrome. The clinical characteristics of our patients show how difficult it is to establish rigid criterions for the distinction between severe epileptic encephalopathies and childhood functional epilepsies. Frequency and duration of crises, the stage of cerebral maturation, and the incidence and frequency of previous cerebral lesions all are important factors on the establishement of severe epileptic syndromes.