Additional Study Information: The purpose of this study is to measure how safe eflornithine is in combination with temozolomide in patients with newly diagnosed glioblastoma multiforme (GBM) following radiation therapy. Safety and tolerability will be determined on the basis of physical exams, laboratory tests, and questions about any problems you might experience during the study. This study will also measure levels of eflornithine in patients following dosing, and it will evaluate how effective eflornithine is as a treatment of GBM when combined with temozolomide. Eflornithine is an experimental drug, which means that it is still being tested in research studies and has not yet been shown to be effective in treating your disease or approved for use by the general public by regulatory authorities, such as the United States Food and Drug Administration (FDA). Temozolomide is approved by the FDA in the United States for patients with GBM. Temozolomide may promote cell death and reduction in tumor cells over a period of weeks to months, eflornithine may function to extend the strength of treatment benefit by making it more difficult for the treated tumor cells to re-start their uncontrolled growth by stopping the pathways needed to re-start cell division. These two drugs are being studies together to maximize how effective they are at treating this type of cancer. Patients will receive one of three dose levels of eflornithine. Initial groups of patients will receive a lower dose of eflornithine, and based on the observed safety and tolerability subsequent groups of patients will receive higher or lower doses of eflornithine. All patients will receive a standard dose level of temozolomide.