A series of 18 patients with primary cerebral lymphoma (PCL) is presented. The clinical, radiological and histological findings are shown along with the results of treatment. Patients were aged 21-76 years (mean 61 years) with a male predominance of 1.6:1. Computed tomography (CT) scans were performed on 15 patients. Typically lesions were multiple, isodense, and showed uniform enhancement with contrast medium. Immunocytochemical studies demonstrated 15 B-cell and 3 T-cell lymphomas. The overall median survival from diagnosis was 3 months. Survival was improved with radiotherapy to 9 months. The difference in survival between those patients treated with surgery and steroids alone, and those who, in addition, received radiotherapy was statistically significant (p less than 0.05). We discuss the results of treatment of PCL in both this series and the literature. We also consider the increased incidence of PCL seen in this unit in 1987 and 1988 and the possible reasons for it.