We describe a patient with systemic lupus erythematosus (SLE) with severe organic brain syndrome, who showed diffuse low density areas in the cerebral white matter on computed axial tomography (CAT) scans. A 43-year-old woman with SLE showed disturbances in various intellectual functions, followed by the development of consciousness disturbances and urinary incontinence. CAT scans, single photon emission computed tomography (SPECT) and cerebrospinal fluid (CSF) interleukin 6 (IL-6) were serially examined during the clinical course before and after treatment with high doses of prednisolone. CSF IL-6 activity paralleled the central nervous system (CNS) disease activity most consistently. By contrast, the diffuse low density areas in cerebral white matter on CAT scans as well as the decreased blood flow in the cerebral cortices on SPECT persisted long after the improvement of the CNS manifestations. Magnetic resonance imaging (MRI) scans also revealed the diffuse areas of increased signal intensity in the subcortical white matter on T2 weighted images. The diffuse lesions in the cerebral white matter are considered to reflect the edema as well as other irreversible changes that have resulted from the disturbed cerebral circulation presumably due to the diffuse microangiopathies in the cerebral cortices and not to be necessarily correlated with the CNS disease activities. Moreover, it is suggested that the inflammatory process evidenced by the elevation of CSF cytokines in addition to the disturbed circulation in the cerebral cortices might play an important role in the pathogenesis of CNS lupus in our patient.