The prognosis for primary cerebral non-Hodgkin's lymphoma has improved markedly in the under-70 age group with the introduction of combined chemotherapy and radiotherapy. A review of our patients has revealed difficulty in obtaining definitive histology initially in 21% (9/43). We investigated the role of corticosteroids in these patients and found an idiosyncratic response in that there was no significance either of the cumulative dose (p > 0.424) or the length of treatment (p > 0.453) with the observed regression of lymphoma with corticosteroids. In order to avoid indiscriminate corticosteroid administration we have formulated a management protocol the entry point for which is a patient with enhanced computered tomography appearances of primary cerebral lymphoma.