Seven patients with infantile spasms, not controlled by the use of anticonvulsant drugs, were treated with Mogadon, 5 to 10 mg daily. They were studied from the clinical and electroencephalographic points of view. The authors concluded: 1. There was marked decrease on the intensity and number of groups of infantile spasms in all cases treated with Mogadon. 2. The best results were obtained in those children who had normal psychomotor development until the onset of infantile spasms. 3. The interval between the onset of infantile spasms and the treatment with Mogadon, and the previous unsuccessfull treatment with ACTH, did not interfere with the results obtained in our patients. 4. In 5 out of 7 patients there was slight improvement of the mental status, although not marked as the decrease of seizures. This improvement was more evident in those children who had previous normal psychomotor development. 5. In those cases who had hypsarhythmia the EEG changes disappeared at the end of the first week of treatment. 6. The patients who had grand mal discharge in their EEG before treatment experienced increase of this discharge after Mogadon. 7. Two children who had not grand mal seizures before treatment developed this type of seizure after Mogadon, coincident with the increase of grand mal discharges in their EEG. These changes spontaneously disappeared after 3 months of treatment. 8. In 3 cases, after the disappearance of grand mal discharges, the EEG showed focal discharges.