In the neoplastic progression of a diffuse astrocytoma, microscopically identifiable features arise that can be used to infer a prognosis that is worse than that associated with a diffuse astrocytoma, but better than implied by the diagnosis of glioblastoma. These features can be used to characterize the intermediate grade neoplasm, the anaplastic astrocytoma. The term, anaplastic, is unfortunate. Most pathologists recognize the term, in other systems, as referring to the most undifferentiated of neoplasms, not an intermediate stage. However, history and neuropathologic practice recognize it and we shall continue its usage.