During the first treatment day of each 28 day cycle you will receive Avastin. Your blood pressure will be monitored, and you will have a physical examination, a neurologic examination, and an evaluation of your performance status (how well you are functioning in daily activities). On the same day, you will begin temozolomide chemotherapy. You will have a blood sample drawn for laboratory tests (approximately 2-3 tablespoons), and a urine sample taken. You will be asked by the study doctor about any health problems you have and medications you take. Additional blood samples may be drawn at the discretion of your doctor as part of your standard care.