We have retrospectively examined the outcome of 41 patients with high grade non-Hodgkin's lymphomas (NHL) and central nervous system (CNS) involvement who were treated with and without radiation at a single institution. Group I consisted of 25 patients with CNS involvement at presentation and Group II, of 16 with CNS involvement at first relapse. All 41 had systemic disease at diagnosis and received systemic and intrathecal chemotherapy. Response to therapy did not differ whether patients received concomitant radiation or no CNS radiation. Thirteen of 16 non-irradiated (81%) and 8 of 9 irradiated Group I patients (89%) achieved complete responses. Three of 4 non-irradiated (75%) and 7 of 12 irradiated (58%) Group II patients achieved complete responses. CNS relapse patterns were similar whether or not patients were irradiated, and regardless of radiation dose. Most patients (18) failed systemically; there were few (6) isolated CNS relapses. Survival was not improved by the addition of radiation. Of the 15 patients who achieved long term survival, 13 remained disease-free throughout their clinical course: 7 of these 13 patients (all Group I) did not receive CNS radiation and 6 (4 Group I, 2 Group II) did. In this series, in which 44% of patients who presented with CNS disease and 13% of those who relapsed with CNS became long term disease-free survivors, there was no discernable benefit from radiation, but increased toxicity was observed.