Between 1980 and 1993, 26 patients were treated for primary lymphoma in the central nervous system at the Norwegian Radium Hospital. This is a rare disease with poor prognosis and thus represents a great therapeutic challenge. Immunocompromised, e.g. AIDS patients, are a group at high risk, but the incidence has increased among immunocompetent patients as well. Median patient age was 64 years; and none of the patients had any signs of immunodeficiency. 23 of the patients received radiation therapy. 13 of the patients received some form of chemotherapy. The overall median survival was 19 months. WHO performance status 0-2, unifocal lesion, absence of steroid dependency and normal serum levels of LDH were all associated with longer survival. Although complete remissions were achieved in most patients, relapses in the central nervous system were frequent.