Little is known about brain tumors in early infancy. Investigators reviewed the records of 27 patients (12 boys and 15 girls) diagnosed within 120 days of birth. The median age was 66 days (range, 0-110 days) at diagnosis. All patients underwent surgery; 18 received adjuvant chemotherapy, and 3 received adjuvant chemotherapy and radiation therapy. The median follow-up was 2.1 years (range, 0.2-21.6 years). At last encounter, 15 patients were alive, and 11 had no evidence of disease. Ten patients died of progressive disease, and 2 died of treatment-related complications. All survivors experienced late effects, including endocrine, neurologic, and cognitive deficits. Of the 13 patients who completed neurocognitive assessments, 7 had an IQ score less than 70. Children in whom brain tumors arise during early infancy can be cured with conventional therapy; however, contemporary approaches can adversely affect long-term function, and families need to be aware of these effects when making therapeutic decisions.