Adult patients with a magnetic resonance scan suggestive of a supratentorial low-grade glioma should generally undergo at least a stereotactic biopsy to confirm the diagnosis and rule out an anaplastic glioma or a non-neoplastic lesion. Early tumor treatment should be given to patients with newly diagnosed low-grade gliomas who are over age 50 years, those who have headaches or neurologic deficits other than seizures, or those whose neuroimaging studies show tumor growth or mass effect. For younger patients presenting with seizures and no other neurologic symptoms, it is reasonable to defer therapy until there is clinical or radiographic tumor progression. When it is judged that intervention is necessary, patients should undergo the maximal surgical tumor resection, which preserves or improves neurologic function. For younger (>50 years) astrocytoma patients with a good tumor resection, radiation may be deferred until tumor progression. Early radiation should be given to astrocytoma patients who are older than 50 years of age at diagnosis (regardless of the type of surgery) or to younger patients who are judged to require early intervention but who are not candidates for aggressive surgical resection. The radiation dose for low-grade glioma should be 4500 to 5000 cGy, preferably with three-dimensional conformal ports. The same guidelines for management apply to patients with low-grade oligodendroglioma or oligoastrocytoma, except that chemotherapy is a reasonable alternative to radiation when it is judged that treatment other than surgical resection is required.