OBJECTIVES: I. Determine whether the use of radiosurgery (stereotactic external-beam irradiation) prior to conventional radiotherapy with carmustine (BCNU) improves overall survival compared to conventional radiotherapy plus BCNU alone in patients with supratentorial glioblastoma multiforme. II. Determine and compare the frequency and severity of toxicities associated with these regimens. III. Compare the effects of these two regimens on neurologic function and quality of life.