In a retrospective analysis of 80 patients with systemic lupus erythematosus (SLE) seen over a 10-year period, 41 (51%) exhibited neurological manifestations. Nervous system involvement was characterized by a significantly greater involvement of black patients (P less than 0-02), a higher incidence of renal failure after the first appearance of neurological features (P less than 0-05), and a significantly worse 10-year survival rate (P less than 0-05). Specific neurological investigations were generally unhelpful in diagnosis. The finding of hypoglycorrhachia in 4 patients was striking and may have pathogenetic significance. The lack of a specific diagnostic test for central nervous system involvement may have hindered recognition of a cerebral abscess in one patient. Treatment with massive doses of corticosteroids was not obviously more effective than treatment with smaller doses. Autopsy findings showed scattered small cerebral infarcts but vasculitis was apparent in only one case.