Adult supratentorial gliomas continue to be one of the most challenging diagnostic and therapeutic problems for the neuro-oncologist. Despite a variety of therapeutic approaches, local control and survival rates remain disappointingly low, largely due to a relative inability to localize diffusely infiltrating glial tumor cells. FDG PET provides a relatively noninvasive method for studying glucose metabolism in normal and pathologic brain tissues. In order to assess the usefulness of FDG PET in a prospective cohort of patients, a group of 31 glial tumor patients underwent serial FDG PET scans at specified evaluation time points: initial or perioperative scan; scan following completion of radiation or chemotherapy; scan(s) at 3-month follow-up intervals until last follow-up exam or death. FDG PET score categories were established to provide a visual and clinically useful means for assessing tumor progression and response to treatment. Both progression-free and overall actuarial survival were determined. There were a total of 137 scans interpreted, on a semi-quantitative basis, by two board-certified radiologists. Patients with high FDG PET scores were more likely to progress clinically and demonstrated lower overall actuarial survival times and revealed statistically significant correlations with other determinants of survival (p < 0.05, Kaplan Meier). Further prospective studies on an expanded patient population are necessary in order to define the role of FDG PET, compared with conventional magnetic resonance imaging (MRI) and computed tomography (CT), in the evaluation and care of patients with malignant gliomas.