Sodium phenylbutyrate is a biological-response modifier that acts as a dose-dependent inhibitor of glioma cell proliferation, migration, and invasiveness in vitro, possibly by inhibition of urokinase and c-myc pathways. Despite its biological activity in vitro, there have not been any prior reports of efficacy in the treatment of human malignant gliomas. We report a 44-year-old female with a recurrent, multicentric, malignant glioma who experienced a durable remission lasting more than four years. The patient initially presented with seizures caused by a biopsy-proven anaplastic astrocytoma of the frontal lobe. The patient was treated with radiation therapy and Procarbazine-CCNU-Vincristine (PCV). However, the tumor progressed and extended to the corpus callosum with midline shift, refractory to four cycles of continuous 72-h infusion of BCNU/Cisplatinum. Additional enhancing lesions appeared in the left frontal and left temporal lobes. The patient was started on sodium phenylbutyrate, 18 g daily in three divided oral doses, and reduced to 9 g/day and eventually to 4.5 g/day to eliminate mild, reversible side effects. Four years later, the patient has a KPS functional score of 100%. Phenylbutyrate is a well-tolerated, oral agent that shows potential for the treatment of malignant gliomas. Further studies should be considered to identify a subset of patients that have tumors sensitive to phenylbutyrate, either as a single agent or in combination with radiation therapy or other chemotherapeutic agents.