A case of a choriocarcinoma within the third ventricle in an eight-year-old girl is described. The patient died suddenly five days after operation. The post mortem examination showed an intraventricular hemorrhage with obstruction of the foramina of Monroe. An additional case in a 16-year-old young man, with similar location and without necropsy, is described. Discussion of the primary origin and etiology of these tumors is presented.