Seventy cerebral lymphomas from 37 men and 33 women were reviewed and reclassified using the modified Kiel classification. Fifty two of the patients were over the age of 50 years (age range 23-85 years). Only two patients were known to be immune deficient--one case of AIDS and one renal transplant recipient. Necropsies only were performed on 31 cases, biopsies only in 23 cases, and both biopsies and necropsies in 16 cases. Systemic tumour was found in 16 of 47 necropsy cases. All the tumours available for review were classic diffuse non-Hodgkin's lymphomas. Where immunocytological studies were positive, the tumour cells were of B cell origin. None was of T cell origin, although reactive T cells in the tumours were frequently identified. It is concluded from this and other studies that the incidence of intrinsic cerebral lymphomas is increasing.