Malignant gliomas are one the most aggressive form of brain tumors and the current standard of care, combination chemoradiotherapy, prolongs survival to slightly more than a year after treatment. Current chemotherapeutic strategies produce limited benefit due to the rapid emergence of resistance. New strategies, among other things, are looking to target the prolific vascularization that supports the rapid growth of these malignant brain tumors. Several anti-angiogenic agents are in clinical testing, primarily as “salvage” therapies, after initial disease progression, and among these, the most mature data are for bevacizumab (Avastin), recently approved for salvage by the FDA, having shown success in a few Phase I/II trials. A small number of phase II trials have also provided very preliminary results with the up-front use of this agent, and at least two large Phase III trials are underway to determine whether bevacizumab will provide added benefit to patients with glioblastoma, when added to the initial chemoradiotherapy regimen. This paper lays out the rationale behind using bevacizumab in combination with radiotherapy, and discusses the up-front trials.