Magnetic resonance imaging was sued to examine the brains of 13 patients with systemic lupus erythematosus (SLE) who had experienced symptoms and signs of encephalopathy. All the patients had normal computerized tomographic scans. Four patients with abnormal magnetic resonance imaging studies had active central nervous system disease. None of the 9 patients with normal scans had active nervous system involvement at the time of study. Parenchymal lesions were usually located in the region of the corticomedullary junction or in the deep periventricular white matter. In coronal sections, some of the corticomedullary lesions extended centripetally as thin irregular lines into the white matter approximating the course of penetrating arterioles of the brain. The parenchymal lesions resolved in 4 months in 1 patient, but persisted unchanged in the others despite clinical improvement or a stable clinical course. It is likely that the parenchymal lesions of these patients represent intrinsic vasculopathy of small cerebral vessels and perivascular microinfarctions associated with SLE.