The clinical changes of 2 patients with axo-tonic seizures and of 10 patients with akinetic seizures treated by Nitrazepam were studied. With the treatment there was rapid reduction in frequency of the axo-tonic seizures, the best result being obtained in one patient with isolated seizures, resulted from an infantile myoclonic encephalopathy with hypsarhythmia, and which were abolished after two months of treatment. The other patient presented Lennox syndrome; there was decrease in intensity and frequency of other types of seizures which were occurying associated to the axo-tonic seizures but new types of seizures developed during the treatment. The occurrence of infectious processes aggravated the clinical picture of one patient. Among the patients with akinetic seizures, 5 presented rapid reduction in frequency and severity of seizures since the first day of treatment; in 4 patients the seizures were abolished on the first day of treatment. The interval of time between the onset of akinetic seizures and the beginning of the treatment, as well as the insuccess of previous treatments, did not influence of results. Relapses or intensification of the clinical picture were observed in 5 patients. The aggravation was not definitely related to infectious processes. The increase of dosage had inconstant effect.