Surgical specimens of malignant, supratentorial, astrocytic gliomas from 503 patients randomized on an RTOG-ECOG treatment protocol were examined by central pathologic review. The diagnosis of glioblastoma multiforme (GBM) was made only when one or more foci of coagulation necrosis involving astrocytic tumor cells were identified histologically. Malignant astrocytic neoplasms without necrosis were classified as astrocytoma with atypical or anaplastic features (AAF). The median survival stratifying for treatment for patients with GBM was eight months compared to 28 months for patients with AAF. In most cases the specimens were received with a Kernohan grade. On the basis of these grades, patients with astrocytoma Grade 3 had a median survival of ten months as compared to a median survival of nine months for those with astrocytoma Grade 4. Observations demonstrate that necrosis is a reliable, decisive prognostic factor associated with malignant, supratentorial, astrocytic gliomas. The Kernohan system is of limited value in assessing prognosis for this group of tumors.