Radiotherapy in high doses has been used in cases of symptomatic epilepsy with the purpose of to act against the focal epileptic activity, as coadjuvancy to the common medical treatment. Patients with clinical manifestations of epilepsy in whom convulsive foci were demonstrated in the EEG, have been selected; these foci have been recognized as well localized and well circunscribed, and in all them the etiology has been the same (atrophic lesions), according to the clinical and radiological (craniogram, pneumoencephalogram and arteriogram) examinations. The purpose of a so homogenous group was to study the results to be obtained in similar conditions. Twenty patients have been selected from a group of forty-eight, because it was possible to obtain a good follow-up for at least three months in each case. In all cases, a medical treatment (barbiturate plus hidantoi-nate) has been used in uniform manner, with the purpose of avoiding influence on the judgement of the value of radiotherapy, for it was impossible to interrupt the drug therapy. Radiotherapy has been used in high doses over the epileptic lesion, which had been localized by the EEG. Two different techniques were used; in both 200 kv, 0.5 mm. filter of Cu were employed. Fourteen patients were irradiated in four different areas, of 4 cm. in diameter each one; they received 150 r daily, 2 areas by day, performing an average total of 3,000 r. In the other 6 cases the technique of kinetic convergent radiotherapy was employed, using the Siemens apparatus; each patient received, through a cutaneous area, an average doses of 3,000 r into the focus and 2,000 r in the skin; they received from 100 r to 150 r in the focus daily. Studying the twenty cases individually, there was marked EEG improvement in 4, relative improvement in 8 and no change in 8; there was marked decrease in the number of seizures in 8, relative decrease in 10 and no change in 2; the mental status was markedly improved in 7, relatively improved in 6 and not changed in 7. The authors call attentiori to the following points: a) Radiotherapy seems to act directyl over the focal electric activity, for there was marked improvement in 4 cases, and relative improvement in 8 cases, immediately after its use; in 2 cases there was exacerbation of the focal activity later; b) In all cases there was decrease in the number of seizures just after radiotherapy; it was not possible, however, to associate this improvement only to radiotherapy, for there was increase of seizures in 2 patients when medical treatment was stopped; c) There was improvement of mental status in 13 cases, although it is important to remember that there was also improvement of the cerebral physiology due to the decrease in number of seizures and improvement of the emotional status of the patient related to their better clinical conditions; d) There was no relation between the number of seizures and focal activity evidenced by the EEG; e) There was no relation between the intensity of cerebral focal activity and the mental status of the patient. The authors conclude: 1) Radiotherapy in high doses decrease the epileptic cerebral focal activity; 2) It is impossible to affirm that the clinical improvement is due to radiotherapy only; 2 patients had increase of focal activity far away from radiotherapy, and 2 others presented increase in the number of seizures when medical treatment was discontinued.