The course of 117 children with so-called centrencephalic myoclonic-astatic petit mal (Doose et al. 1970) was evaluated with the question, whether petit mal status can be the cause of dementia frequently seen in these patients. A dementia is found definitely more frequently in patients with petit mal status. With regard to the animal experimental studies of Wasterlain (1978, Lit.) and Meldrum (1978, Lit.) it seems possible that the prlonged generalized hypersynchronous discharges of the petit mal status lead to a serious disturbance of the neuronal energy metabolism and thus to cerebral organic damages or disturbances of the brain development.