A 38-year-old woman suffering from systemic lupus erythematosus was treated with cyclophosphamide and prednisone. Two months later she developed mononeuritis multiplex. After one year, she showed a personality change with aggressiveness and paranoid delusions. Grand mal epileptic fits began to occur. An unenhanced CT-scan showed extensive and bilateral frontal hypodense lesions originally ascribed to vasculitis-caused infarcts. On autopsy, a primary intracerebral lymphoma with extensive necroses was demonstrated. The relationship between SLE, immunosuppressive treatment and primary intracerebral lymphoma is discussed.