Primary lymphomas of the CNS are rare tumors accounting for less than 2% of all extranodal non-Hodgkin's lymphomas. The treatment for this disease has been disappointing. Radiation therapy and surgery have produced consistently poor control of this disease, with a median survival of 15 months. We have reviewed ten cases of primary lymphoma of the CNS treated at the Joint Center for Radiation Therapy or Dana-Farber Cancer Institute (Boston) from 1968 to 1981. All patients had biopsy-proven CNS lymphomas without systemic disease at presentation. In our series, control of CNS lymphoma was seen only in patients receiving craniospinal radiation or CNS-penetrating chemotherapy.