The most important prognostic factor in malignant gliomas is histopathological diagnosis of the tumor. The survival of patients with anaplastic astrocytoma is much longer than that of patients with glioblastoma. The median survival of the former has been improved up to almost 4 years by the recent progress of multidisciplinary treatment, whereas that of the latter has still remained in less than 1.5 years. Other important factors proved to be associated with survival of patients with malignant gliomas are the age of patients, Karnofsky performance status on admission, surgery, radiotherapy and chemotherapy. There is substantial evidence suggesting an association between younger patient age and longer survival in adults with supratentorial anaplastic astrocytoma as well as glioblastoma. It is also consistent with evidence that the patients with better performance status on admission live longer after treatment. Gross total resection of supratentorial anaplastic astrocytoma is directly associated with longer and better survival when compared to subtotal or partial resection. For glioblastoma, however, gross total resection has not been proved to have a significant survival advantage over subtotal or partial removal. Radiotherapy has been proved to be associated with longer survival of patients with supratentorial anaplastic astrocytoma and glioblastoma. Chemotherapy has not proved effective in prolonging the survival of patients with glioblastoma. Multidrug chemotherapy with CCNU, procarbazine and vincristine has proved to have significant survival advantage over BCNU alone, suggesting chemotherapy is also a prognostic factor in patients with anaplastic astrocytoma.