Patients may consent to provide tumor tissue, blood, and CSF samples for biological studies. Tumor tissues are analyzed for the activation of the WNT signaling pathway, activation of the SHH signaling pathway, validation of novel patterns of gene expression via immunohistochemical (IHC) analysis; validation of genetic abnormalities via interphase fluorescence in situ hybridization (iFISH); construction of gene expression profiles via microarray analysis; construction of DNA methylation profiling via microarrays; single nucleotide polymorphism (SNP) analysis for DNA copy number aberrations; potential oncogenes and tumor suppressor genes via DNA sequence analysis; expression of a number of cell signal proteins implicated in the biology of medulloblastoma via western blot; expression of additional proteins encoded by genes associated through SNP and gene expression array analysis with clinical disease behavior. Blood samples are analyzed from patients whose tumors contain gene mutations via sequence analysis of constitutional DNA. CSF and blood samples are analyzed for identification of potential tumor markers. Parents may consent to have blood samples analyzed for inheritable gene mutations associated with medulloblastoma.