The management of medulloblastoma in infants is highly problematic and suboptimal.1,4,26,27Owing to the high likelihood of severe neurocognitive damage secondary to whole-brain irradiation delivered as part of craniospinal radiotherapy, most efforts over the last 2 decades have focused on use of chemotherapy in children younger than 3 years, and in some studies, younger than 5 years, either to delay or obviate the need for radiotherapy.26- 28Results of such an approach have been mixed. Early studies using drug combinations such as cyclophosphamide, cisplatin (cis-diamminedichloroplatinum), vincristine sulfate, and etoposide phosphate demonstrated that approximately 40% or less of patients younger than 3 years could be successfully treated with chemotherapy until they reached age 3 years, followed by craniospinal irradiation.26Primarily, those children with extensively resected nondisseminated tumors survived, and in those who survived, craniospinal irradiation delivered at age 3 years likely caused permanent cognitive damage. Subsequent studies attempted to intensify chemotherapy and not use craniospinal irradiation. These studies intensified chemotherapy by increasing drug dosage, with or without peripheral stem cell support, or adding other chemotherapeutic agents including intrathecal agents, and demonstrated possible improvements in progression-free survival, although other factors may also be responsible for this apparent improvement.27,28Approximately 15% to 20% of infants who would previously have been diagnosed as having medulloblastoma harbor a different embryonal tumor, the atypical teratoid/rhabdoid tumor.29This tumor, which can be reliably diagnosed on the basis of immunohistochemical and molecular genetic findings, is associated with an extremely poor prognosis, with few, if any, infants surviving with currently available treatments. The removal of this subset of patients from the medulloblastoma study population will improve reported survival outcomes.