The study of 120 patients, 71 male and 49 female, with electroencefalographic pattern of hypsarhythmia is reported. The electroencephalogram of most of them (39%) was performed when the patients were from 10 months to 3 years old and the first convulsion was registered predominantly in their first four months of life (54%). In 56% of the patients more than one type of convulsion was registered by the anamnesis, the association of infantile spasm and generalized motor convulsion being the most common. In 44% of the patients only one type of convulsion was registered, the most frequent one being the infantile spasm; 18 patients (16%) having not presented infantile spasm. The electroencephalographic alterations were the most varied. The assymetric hypsarhythmia was registered in 22% and the fragmentation in 11% of the cases. There was no response to photostimulation in any one of the patients.