Brain tumors are among the most common forms of cancer in children and account for most cancer-related deaths in this age group. The incidence of brain tumors appears to be increasing in children, while therapeutic advances have been modest. Few genetic studies exist on pediatric brain tumors, in part because tissue from low-grade and brain stem tumors is not readily available, and also because individual centers have relatively few cases. Genetic changes in infiltrating astrocytomas involve genes in the p53 and RB pathways, and show alterations that are similar to infiltrating astrocytomas in adults. The PTC gene is mutated in a subgroup of medulloblastomas, and may lead to increased proliferation in granule cells that normally express this receptor. Further studies are needed to identify genetic alterations in pilocytic and low-grade astrocytomas, which account for 40% of brain tumors in children.