The patient, a 44-year-old female, was admitted to our department because of right hemiparesis and left oculomotor nerve palsy on February 7, 1986. Neither lymphadenopathy nor hepatosplenomegaly was present. She had been treated with prednisolone for systemic lupus erythematosus (SLE) for one and a half year before admission. The CT scan revealed a homogeneously enhanced mass lesion from the midbrain through the thalamus on the right side. The whole body gallium scintigram showed no abnormal uptake except in the brain. Stereotaxic biopsy was performed. Histopathological diagnosis was malignant lymphoma, diffuse, large cell type (International Working Formulation). The enhanced mass lesion disappeared after radiation therapy. Subsequently, she received chemotherapy. She remained well until May 1988 when she died because of the systemic lymphadenopathy. The association of malignant lymphoma and SLE has appeared occasionally in the literature. Primary intracerebral malignant lymphoma associated with SLE is much rarer but it should be considered in the differential diagnosis of symptoms of the central nervous system in a patient with SLE. Therefore, biopsy of a cerebral mass lesion is mandatory if appropriate therapy such as radiation and chemotherapy is to be administered.