Twenty-two SLE patients were examined with Magnetic Resonance Imaging (MRI) and Single Photon Emission Computed Tomography (SPECT). Multifocal areas of cerebral blood flow (CBF) defects were found in 81.8% of the patients. These alterations were present in patients with severe neurological disorders, in those with neuropsychiatric symptoms only, and also in asymptomatic cases. Anticardiolipin antibodies (aCL) were detected in all patients, but no correlation was found between serum aCL positivity and neurological involvement. The high incidence of cerebral blood flow disorders found in asymptomatic patients, and their poor correlation with the MRI alterations suggest a primary defect of CBF in these patients.