Inclusion Criteria: - Histologically confirmed germ cell tumor or elevated AFP or B-HCG in the setting of radiographic disease consistent with a germ cell tumor. Disease must be confined to the central nervous system. - Participants do not need to have measurable disease. Most patients will not have measurable disease at the time of treatment. - 3 years of age or older and 25 years of age or older a the time of diagnosis because this study evaluates this disease entity in the pediatric population which may differ from the adult population. - Life expectancy of greater than 12 months. - ECOG performance status of 0, 1 or 2 - Baseline MRI of the brain and spinal axis with gadolinium and prior to any chemotherapy is required. If surgical resection is performed a post-operative MRI is required. If the patient receives chemotherapy prior to radiation, a post-chemotherapy MRI of the brain is required. If spinal involvement was seen on initial MRI and prior to chemotherapy, a MRI of the spine is required after chemotherapy and prior to radiation. - Serum and lumbar CSF must be obtained to evaluate for alpha fetoprotein (AFP) and beta human chorionic gonadotropin (HCG). This is needed to stratify patients into pure GCT and NGGCT. - Women of child-bearing potential and men must agree to use adequate contraception prior to study entry and for the duration of study participation. Exclusion Criteria: - Patients will be ineligible if any prior therapeutic radiation therapy > 200 cGy has been delivered to the central nervous system. - Patients will be ineligible if chemotherapy was completed greater than 1 year from the planned start date of radiation therapy or if the patient is referred for radiation therapy after a relapse following a regimen with chemotherapy alone. - Individuals with a history of a different malignancy are ineligible except for the following circumstances: Disease-free for at least 5 years and are deemed by the investigator to be at low risk for recurrence of that malignancy. Individuals diagnosed and treated within the past 5 years for cervical cancer in situ and basal cell or squamous cell carcinoma of the skin. - Pregnant females