One hundred infants with intracranial tumors symptomatic during the 1st year of life were studied. They differed from older children in having a higher percentage of supratentorial tumors and in the fact that 90% of the tumors were of neuroectodermal origin. Vomiting, alteration of psychomotor development, and macrocrania were the most common presenting features. The "diencephalic syndrome" was seen in 5 infants, and subarachnoid hemorrhage due to tumor was diagnosed in 4. Computed tomography as the primary investigation is increasing the number of neoplasms diagnosed in this age group, although review of the skull roentgenograms in the series disclosed an abnormality in 92%. Eighty of the tumors were verified, 68 by a cranial operation and the rest at autopsy. Of the verified neoplasms, 20% were medulloblastomas, 12.5% were choroid plexus papillomas, and 10% were cerebellar astrocytomas. The cumulative average survival was 27 months but, for those who underwent a tumor operation, the average survival was 37 months. The operative mortality was 30%. Thirty-nine patients were irradiated, and this subset had a 5-year survival rate of 43%. The morbidity was high irrespective of radiotherapy; 60% of those who survived 1 year were moderately or severely disabled. Those infants receiving more than 5000 rads of whole brain radiation tended to have greater deficits in the long term. When analyzed separately, patients treated after 1970 had greatly improved mortality and morbidity rates.