Primary central nervous system lymphoma (PCNSL) is widely regarded as one of the primary brain tumors most amenable to treatment. Although whole brain radiotherapy was the cornerstone of therapy for decades, recent work clearly indicates that chemotherapy has become the primary focus of treatment for this disease. The initial treatment of PCNSL for all patients, including the elderly, should be chemotherapy using a high-dose methotrexate-based regimen. Although cranial irradiation has often been combined with methotrexate, the unacceptably high incidence of late neurotoxicity, particularly in older patients, has caused many to eliminate radiotherapy, especially in those older than age 60 years. Emerging data support the validity of this approach, and the development of more efficacious chemotherapeutic regimens has been the focus of recent research.