This work was developed in order to verify the rate of occurance of the etiological factors which may actuate in cases of behaviour disturbs, when the basic symptoms are irritability, agressiveness, impulsiveness and psycho-motor instability; 100 observations were reviewed, of patients of both sexes, whose ages varied withing the range of 5 to 16 years old and who were assisted at the Child Psychiatry Service, University of São Paulo School of Medicine. In 15 of these patients it was not possible to make clear the organic circumstances or psychological factors which might be directly related to the etiology of such above mentioned disturbs. As to the remaining patients, etiological factors were found which are probably related to the clinical chart in the following rate of occurance: cerebral disrythmia, in 69 cases; unfavourable environment conditions, in 37 cases; oligophrenia, in 35 cases; cerebral damage, in 3 cases. The importance of the environment factors and oligophrenia in the genesis of behaviour disturbs is already well known and, therefore, their rate of occurance does not cause any surprise. It was unexpected, however, the high incidence of cerebral disrythmia in this work: 68% against approximately 10% found among the population in general, according to the monographs about epilepsy and electroencepholography. So great a difference exempts any statistic analysis and indicates an extremely important factor in the origin of behaviour disturbs which, however, is not usually valuated and not even mentioned in the studies about that subject. The final conclusions of this work suggest a reviewal in the therapeutics of behaviour disturbs. Together with the pedagogic and psychotherapic methods, the sole ones usually recommended, also the anti-epileptic treatment must be included, once in our experiments this treatment can provide good results over irritability, agressiveness, impulsiveness and instability shown by patients with cerebral disrythmia.