 Bevacizumab, irinotecan, and temozolomide are three agents shown to have promising activity in a variety of central nervous system tumors. No prospective studies have been published or are currently in progress within the major consortiums with this combination of drugs. Brain tumors are the second most common cause of cancer in pediatrics and the leading cause of cancer death in children. For children with High Grade Gliomas or with relapsedrefractory brain tumors, new agents in new combinations are needed. Historical data shows that newly diagnosed high grade gliomas 5 year progression free survival is 28-42. Recurrent malignant gliomas median survival is 3-9 months. Recurrent medulloblastomas 2 years survival is 9. This study is a phase I study designed to provide an objective observation of toxicity and establish a maximum tolerated dose of this combination. In addition, this study will observe the response of children with relapsed or refractory central nervous system tumors. 