Approximately one-sixth of all brain tumors occur in children under fifteen years of age. French (8), reporting from the University of Minnesota Hospitals, stated that 1 per cent of all patients admitted to the pediatric service had a brain tumor. There seemed to be a peak incidence at two years and again at six years. Stern (16) states that over onehalf of the brain tumors in children occur during the first five years of life, and in Pilcher's (15) series 40 per cent of the children were seven years of age or younger. Of 427 tumors in patients under fifteen years of age, 6 were seen in infants less than a year old. Gross (9) studied 9 cases of primary brain neoplasm occurring in the first two years of life. Of our group of 34 brain tumors in patients whose ages ranged from eleven months to fifteen years, 19 were in children six years of age or younger. Most authors agree that two-thirds of the brain tumors in children occur beneath the tentorium. The majority of these are highly malignant. In a study of four large series of cases, gliomas were found to make up 70 per cent of the total. Of 154 brain tumors in children studied by Cushing (3), there were 116 miscellaneous gllomas, 21 congenital tumors (of which the majority were suprasellar cysts), and 6 tuberculomas. The cerebellar and fourth ventricle tumors and tumors of the pons and medulla make up the group of subtentorial tumors. Davis (5) groups the medulloblastomas, astrocytomas, and ependymomas under the term “midline cerebellar tumors.” The medulloblastomas may arise from the roof of the fourth ventricle, vermis of the cerebellum, or posterior part of the middle of the cerebellum. The astrocytomas usually arise from one cerebellar hemisphere, but may take origin in the midline above the fourth ventricle. In many cases these tumors are cystic. The ependymomas arise from the walls and floor of the fourth ventricle. The tumors of the pons and medulla are most often highly malignant, infiltrating gliomas. Cushing stated that the astrocytoma of the cerebellum is twice as common in childhood as the medulloblastoma. French found astrocytomas nearly four times as common as medulloblastomas, but he had a large group of supratentorial tumors and included the astrocytomas in this region. Bucy and Haverfield (2) reported that 25 per cent of their subtentorial tumors were astrocytomas and 20 per cent medulloblastomas. Keith and his associates found astrocytomas and medulloblastomas of equal frequency beneath the tentorium (11). Stern, however, had 11 medulloblastomas in his series, with 6 cerebellar and 6 pontine astrocytomas. Our subtentorial tumors included 5 astrocytomas (Fig. 1) and 7 medulloblastomas (Fig. 2), all of which arose in the cerebellum or the fourth ventricle.