Magnetic resonance imaging (MRI) of the brain is a sensitive method to detect parenchymal tissue lesions. Its value in the diagnosis of central nervous system (CNS) lupus is disputed. To address this question, we have conducted an open and prospective study in a population of 44 SLE patients. We investigated 24 patients (mean age 33 +/- 13 yr) with past or active CNS lupus (group A) that included organic brain syndrome (12), migraine (8), focal neurological signs (7), seizures (2), myelopathy (1) and narcolepsy-cataplexy (1), and 20 patients (mean age 32 +/- 12 yr) without CNS lupus (group B). Health controls comprising nine females and one male aged 31 +/- 9 yr were also studied for comparison (group C). MRI was performed using sagittal T1-weighted images, axial and coronal spin density, and T2-weighted images. All scans were read blindly. Thirteen patients in group A and 10 in group B had well-identified lesions on sequences with long repetition time. Lesions were mostly multiple, small, punctate areas of increased signal at periventricular or subcortical white matter of both cerebral hemispheres. The number and location of lesions were not significantly different in both groups. None of the group C patients had MRI lesions. The presence of lesions was significantly associated with age at study and disease duration, but not with the presence of CNS lupus. In summary, MRI abnormalities are detected in neurologically asymptomatic SLE patients. Whether this represents subclinical brain involvement remains unknown.