Results of radiation given to patients with AIDS-related high-grade CNS lymphoma have been disappointing, with short survival times due to infection complications. However, complete response has been documented after radiation in some patients. High-dose MTX will be used to improve the possibility of a greater antineoplastic response than that obtained by radiation alone. Since the underlying immunodeficiency state is not affected by therapy directed against the lymphoma, patients are still prone to life-threatening opportunistic infections or relapse of lymphomatous disease within the CNS. Accordingly, AZT will also be used in an attempt to alter the overall natural history of the disease.